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MISC: 1984 FLOOD PLAIN MANAGEMENT STUDY - BIG PIPESTONE CREEK MISC: 1984 FLOOD PLAIN MANAGEMENT STUDY - BIG PIPESTONE CREEK • FLOOD PLAIN MANAGEMENT STUDY BIG PIPESTONE CREEK JEFFERSON COUNTY, MONTANA `#rz s c ' oa J-GS`{ ' x , ^ . tl' ;E«+tpst e,7 t4 pq F „iibi "... r. r Prepared by UNITED STATES DEPARTMENT OF AGRICULTURE . • 50 5 SOIL CONSERVATION SERVICE 9 % ' p� Bozeman, Montana 'veer cow • In cooperation with JEFFERSON COUNTY WHITEHALL TOWN COUNCIL JEFFERSON VALLEY CONSERVATION DISTRICT MONTANA DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION FLOOD PLAIN MANAGEMENT STUDY ' Big Pipestone Creek ' Jefferson County, Montana 1 Prepared by ' UNITED STATES DEPARTMENT OF AGRICULTURE SOIL CONSERVATION SERVICE Bozeman, Montana 1 in cooperation with ' Jefferson County Whitehall Town Council Jefferson Valley Conservation District ' Montana Department of Natural Resources and Conservation 1 September 1984 1 T A B L E O F CONTENTS Page INTRODUCTION 1 ' STUDY AREA DESCRIPTION 2 LOCATION MAP following page 2 NATURAL VALUES 9 ' FLOOD AND EROSION PROBLEMS 10 FLOOD PLAIN MANAGEMENT 17 ' APPENDIX A Map Index and Flood Hazard Maps APPENDIX B Flood Profile Sheets ' APPENDIX C Selected Cross Sections APPENDIX D Supplementary Data Tables ' Table 1--Flood Discharges for Selected Frequencies for Study Reaches D-1 Table 2--Flood Frequency-Elevation Data D-2 I Table 3--Increased Depth-Remaining Floodway Width Values . . . D-5 Table 4--Acres Flooded D-7 APPENDIX E Elevation Reference Marks E-1 APPENDIX F Investigation and Analyses F-1 ' APPENDIX G Glossary of Terms G-1 ' APPENDIX H Bibliography H-1 ' APPENDIX I Legal Reference I-1 ' BIG PIPESTONE CREEK FLOOD PLAIN MANAGEMENT STUDY Whitehall, Jefferson County, Montana ' September 1984 INTRODUCTION ' This study was requested by the Jefferson Valley Conservation District in ' cooperation with the Whitehall Town Council and the Jefferson County Commissioners. 1 The request for the study was carried forward in accordance with the Joint ' Coordination Agreement between the Montana Department of Natural Resources and Conservation (DNRC) and the Soil Conservation Service (SCS) which was originally signed on June 20,1975 and later revised on March 16, 1979. 1 A plan of study. for this Big Pipestone Flood Plain Management Study was ' prepared to develop detailed information relating to hydrology, hydraulics, and flood hazards for the study area and to develop possible solutions to problems in the area. The plan of study was signed by the Jefferson Valley ' Conservation District, the Jefferson County Commissioners, the Whitehall Town Council, DNRC, and SCS on August 23, 1983. The study was then authorized by the Chief of the Soil Conservation Service on October 12,1983. 1 1 •1- The objectives of the sponsors for this study were: ' 1. To obtain detailed flood plain and related information. 1 2. To identify feasible measures to reduce the flood hazard, high water tables, and sediment deposition along the south edge of the town of Whitehall. 3. To identify potential alternatives to stop further channel , headcutting and bank erosion resulting from past channel straightening activity west (upstream) of Whitehall. ' 4. To establish sound flood plain management in accordance with Montana law. , The only existing information relating to the study reach was a preliminary , study prepared for the Jefferson Valley Conservation District which addressed the channel erosion problem on Big Pipestone Creek. Other information for this study was obtained from the sponsors, the U.S. Forest Service, the U.S. , Geological Survey, the U.S. Army Corps of Engineers, and local residents. 1 STUDY AREA DESCRIPTION The study reach involves a 6.5-channel-mile reach on Big Pipestone Creek, which flows from west to east along the south side of Whitehall, Montana. This reach was studied in detailed intensity. (See Location and Study Area Map. ) -2- I R 8W R.7W R.6W R.5 W. R 4W r J s jJ�`f ;. .-f� Vic' 4i I i „1+�.2- �:lc--4-4'--t\��S� (1( l,,,\\m -11 ; a ., s C�j}- "°I l l 0-144 mrrrr_7 a�.=,{ •i •ii i ,�j., ,•• �.1 VII*�T;}, �' 77 1 /��'. 5 1 r I; ( ,r. Fee -•'r Prt J-' .o IIC t�h ` I, '1- • � \m• Net j* � . �- Mine \ i ±s' ir „ a /)j VI�� :�r� ��11 � e��j� r � ` I h� -lr rr( ka Fc- r - -4 I �. n 1 H � 11 '4 4 r. Fgr �.� �1 I} ■' y— r 61 ' t i dt e' $Jt; k - 4± .o D rr455 1.er I , � arB,v SitNrF'AA3F s 1 ( n-r, fu,� ;01'7 Cato w. a �K\'‘. ' 1 I " -- P ill 1 f/4 Vedom ■ � r- 1 -21 2( ill\ 7--- ( _ t f I { r DRAINAGE AREA BONY 4 dame `�-'`I STUDY AREA �-:5� rE * 'I_ � ,,®' -...____./ a l s - _ yyp^^\\�� 1 JEFFERSON CO �■ LOCATION MAP 1 study area BIG PIPESTONE CREEK FLOOD PLAIN MANAGEMENT STUDY I LOCATION MAP JEFFERSON COUNTY. MONTANA NOTE: Location map base is from the Butte ' and Dillon AMS Quads, 1:260,000. SCALE: 1 inch=4 miles 1 Whitehall is in Jefferson County in southwestern Montana, about 22 miles east of Butte, Montana, and about 16 miles east of Homestake Pass on the Continental Divide. According to the 1980 census, the population of Whitehall was 1,030 (Reference 1) . In 1982, the population of Jefferson County was estimated at 7,300 (Reference 2). 1 The downstream end of the study reach for Big Pipestone Creek begins at the confluence with Jefferson Slough, a secondary channel of the Jefferson River. This point is located about 1 mile southeast of Whitehall near the southwest corner of Section 2, Township 1 North, Range 4 West. The upstream end of the ' study is about 4 miles west of Whitehall at the U.S. Highway 10 crossing in the southeast quarter of Section 35, Township 2 North, Range 5 West. 1 The Big Pipestone Creek drainage starts at the Continental Divide to the west and north of the study reach. A major tributary in the Big Pipestone Creek ' watershed is Little Pipestone Creek which joins the main creek just below U.S. Highway 10 near the upstream end of the study area. The Little Pipestone Creek drainage borders the Big Pipestone Creek drainage on the south and also heads at the Continental Divide. The drainage area of Big Pipestone Creek just above the confluence with Little Pipestone Creek is 114.4 square miles. Little Pipestone Creek adds 46.9 square miles of drainage area, giving a total area at this point of 161.3 square miles. The total drainage area increases to 169.3 square miles at Montana Highway 55 which crosses Big Pipestone Creek ' on the southwest edge of Whitehall. From that point downstream to the confluence with Jefferson Slough, the channel flows out onto an alluvial fan -3- 1 and the drainage area is increased only slightly to a total of 170 square , miles. The highest elevation in the watershed near the Continental Divide is 8,625 National Geodetic Vertical Datum (NGVD) . This drops to about elevation 4,450 NGVD at the upstream end of the study reach and then to elevation 4,330 NGVD at the downstream end. Delmoe Lake Dam, a major irrigation storage reservoir, is located in the upper part of the watershed on Big Pipestone Creek and controls an area of 23.5 square miles. The dam and reservoir are owned and operated by the Pipestone Water Users Association, a private nonprofit organization consisting of 14 stockholders who are the sole users of the stored water. Delmoe Lake Dam was constructed by a private developer in 1913 and 1914 for the purposes of developing and selling irrigated lands. In 1942 the project was purchased by the Association. Delmoe Lake Dam is a 60-foot-high hydraulic earth fill structure with a ' central concrete cutoff wall. The dam is 290 feet across the top. It has a top width of 40 feet, an upstream slope of 3:1 and a downstream slope of 2:1. The upstream face is riprapped for wave protection. There are two 24-inch barrels incased in concrete that go through the fill for the purpose of releasing water. The operation of this outlet is manually controlled by a gate structure on the upstream end to regulate the storage in the reservoir and the release rates from the dam. The emergency spillway consists of a 1 25-foot-wide, 300-foot-long, unlined channel section on the right abutment cut in decomposed granite and rock (Reference 3) . _4_ 1 ' Originally, a concrete wall was built across the spillway flush with the crest. However, in 1983, a new concrete weir wall was built across the spillway, raising the crest about one-half foot. This structure also has ' provisions to add stop logs which could raise the crest an additional 2 feet. The storage of the dam at the original spillway crest is 6,585 acre-feet. The elevation of the original crest was 60106.4 NGVD. The top of the dam is about 9 feet higher at elevation 6,110 NGVD (Reference 3) . The storage at the top of the dam is about 9,300 acre-feet. The present maximum capacity of the emergency spillway is approximately 1,600 cubic feet per second. About half of the entire Big Pipestone Creek watershed is within the Deer Lodge National Forest boundary. About two-thirds of the area is typical ' forested mountain terrain. The lower third is open rangeland on foothill ' terrain. The study reach is almost entirely pasture or hayland, much of it irrigated. Urban development is limited to areas within or near Whitehall. ' Very little activity is presently taking place in flood plain areas in the study reach. The climate in the watershed is continental, characterized by warm summers, cold winters, and semiarid precipitation. The weather station at the airport ' 7 miles southwest of Whitehall (U.S. Weather Bureau Station Whitehall FAA AP) provides the following climatological data for a 21-year period (Reference 4) . ' The average annual temperature was 43.6 °F. The hottest month was July, with an average maximum temperature of 84. 1 °F. The coldest month, January, had an average minimum temperature of 9.7 °F. The extremes ranged from 104 °F in 1 1 -5 1 August to -37 °F in January. The average annual precipitation was 9.64 inches , with 40 percent occurring in May and June. The average annual precipitation at the upper end of the Big Pipestone watershed on the Continental Divide is about 25 inches (Reference 5) . Soils in the watershed consist of shallow sandy and silty soils over granite , bedrock with several areas of exposed bedrock in the upper mountainous area. The soils in the lower foothill areas vary from shallow to deep and consist of granitic sand, silt, and loam. The flood plain area in the study reach is deep unconsolidated alluvium consisting of lenses of granitic sand, silt, loam, and clay. Depth to bedrock material in the study reach varies from about 15 feet at the upper end to about 40 feet at the lower end. i The study reach has been subjected to two severe channel changes from man's past activities, particularly in the upper part west of Whitehall. These channel changes have led to some dramatic consequences. The early-day 1 construction of what is now the Burlington Northern Railroad track placed the roadbed parallel to the Big Pipestone Creek channel from Whitehall upstream to the end of the study. Not only did this construction produce the first major channel change, it also served to cut off part of the flood plain available for flood flows. The channel was cut off and straightened for a distance of 2,300 feet between cross sections AO and AQ, about 1 mile east of the U.S. Highway 10 crossing. (See Appendix A, Flood Hazard Maps.) This action ' accounted for reducing the original channel length by 3,500 feet. -6 ' 1 ' The second channel change that precipitated the most drastic channel change occurred about one-half mile below the Smith Ranch in the fall of 1947. This change was probably made by the owner of the property at that time. ' Apparently, the purpose was to move the stream from the middle of his pasture out to the north edge of the pasture along the railroad to allow easier access (Reference 6) . The stream was diverted directly down the south borrow ditch of the railroad and created a 1.3-mile straightened reach. This reach begins near cross section AH about 1.7 miles west of Whitehall and ends near cross ' section AD about 0.3 mile west of Whitehall. (See Appendix A, Flood Hazard Maps. ) This change had the effect of shortening the original channel length by 7,500 feet. This 7,500 feet, plus the reduction of 2,100 feet along the railroad, accounts for a total reduction of 11,000 feet. The original 25,300 ' feet of channel were shortened by 11 ,000 feet to the present length of 14,300 feet, which amounts to a 43-percent reduction in channel length. The result of these channel modifications is to greatly increase channel slope and flow velocities. The stream responded rapidly and started headcuts which have progressed upstream in the straightened channel reaches, eroding tremendous volumes of material by vertical deepening and lateral bank movement. Presently, three headcuts exist in the upper study reach. The first of these is at the Smith Ranch crossing just south of the ranch headquarters at cross section AK. The progress of this headcut is presently halted with rock riprap in combination with the culvert crossing at this ' point. The drop in the channel across this headcut is about 8 feet. This crossing has been maintained by the Smith Ranch as needed. The second headcut is about 1 mile farther upstream near the beginning of the straight section created by the railroad at cross section AR. This headcut is presently I located at an irrigation diversion site on State-owned land leased by Smith I Ranch. Over the years , Smith Ranch has held this headcut at this location ' through the addition of rock riprap and other maintenance. The drop in the channel at this point is about 7 feet. However, the channel does not appear I to have reached astable grade between this headcut and the first one below it. Additional channel erosion wil cause an increase in the drop at this ' location and increase the difficulty of preventing the headcut from ' progressing farther upstream. A third headcut of smaller proportions is present about 0.5 mile above the second headcut. It is just above the old ' county road at the McArthur irrigation diversion structure at cross section BA. There is a drop of about 4 feet at this location. I The volume of material that has been eroded from the straightened channel ' section through the headcutting process is estimated to be about 300,000 cubic , yards at the time of this study. The eroded channel sections average about 13 feet deep and 50 feet wide at the top, and the banks are nearly vertical. The II original channel section was approximately 5 feet deep and 30 feet wide at the top. II 1 The eroded material has been transported into and through the channel reach from Whitehall downstream to the Jefferson Slough. The bulk of this material ' appears to be in the Jefferson Slough; however, it has filled in the Big Pipestone Creek channel in the lower reach. This has decreased the capacity ' of the channel, increased the chances of flooding in Whitehall, and raised , ground-water levels . 1 I _B_ I I PHOTO PLATE 1 I I I I a ` a` + L. (L.C. Hanson Co. Photo Reference 6) Downstream end of second headcut on Big Pipestone Creek at irrigation diversion on State land west of Smith ranch near cross section AQ. (See Appendix A. ) ... .„..H,.: c„.... , t x k t I I (L.C. Hanson Co. Photo Reference 6) ' Looking downstream at the eroded Big Pipestone channel below the headcut at the irrigation diversion near cross section AP. I PHOTO PLATE 2 I 1 IrA I ..yew a,. I t }yy?? ¢ b b c of • _y. t Sinai � e WA. 46e P?"L (L. C- L. C. Hanson Co. Photo - Reference 6) I Upstream end of headcut at Smith ranch crossing on Big Pipestone Creek near cross section AL. $4 aFaxa. K. I ileks r X y } (L.C. Hanson Co. Photo - Reference 6) I Looking downstream on Big Pipestone Creek just below the headcut at the Smith ranch crossing near cross section AJ. I PHOTO PLATE 3 I , t F l I 4R s 'r,3 "3 " in'.," eT, I i I (L.C. Hanson Co. Photo - Reference 6) ' Looking downstream at the straight, eroded Big Pipestone section west of Whitehall. This picture is near cross section AF. A �, L X8` ac..= .. I r Il - (L.C. Hanson Co. Photo - Reference 6) iOriginal Big Pipestone channel located south of present deep eroded section in the photo above. II I PHOTO PLATE 4 I .a pp' - Rip .fir r r. & � . . t Tom ° ei ' 4 .wan - f " av# r I (L.C, Hanson Co. Photo - Reference 6) Big Pipestone Creek channel in the lower reach on south edge of Whitehall near cross section Q. I 3 �pp wt- mow r 2.C. Hanson Co. Photo - Reference 6) I Minor flooding on Big Pipestone Creek on south edge of Whitehall. This picture is located between cross sections R and Q. ' NATURAL VALUES ' The flood plain and accompanying riparian environment of Big Pipestone Creek within the study reach provides limited habitat for wildlife. This is due in ' part to the deeply incised, straightened channel that supports very limited vegetation. The lower reach of the study area is exposed to disturbance resulting from human habitation. The reach of stream above the Smith Ranch 11 brushy shrub and tree vegetation in essentially a natural state. Excellent brushy habitat remains along the length of the original channel now bypassed ' by the modified channel. Woody vegetation of the old channel way consists of western water birch and a variety of willows. This area provides good habitat ' for and is used by mule and white-tailed deer. Much of the upper reach of the flood plain is pasture grazed by domestic ' livestock, while the lower area is hayland. ' Above the channeled section, the stream is rated by the Montana Department of ' Fish, Wildlife and Parks and the U.S. Fish and Wildlife Service as a Value Class IV moderate fishery resource stream. This section of the stream ' supports a modest trout fishery. Fishery values in the study area are low because of active channel erosion and sedimentation. Limited numbers of trout occur in this reach of stream because of its altered and unstable state. No threatened or endangered plants or animals or areas of archeological, historical, or cultural significance are known to exist within the study area. 1 1 -9- 1 The study area contains a vivid example of the consequences of careless channel modification and encroachments. Nature uses a meandering channel and flood plain system to maintain flood flows at low depths and normally safe velocities when healthy streamside vegetation is present. When these natural features are altered, destroyed, or bypassed, erosion is the result. FLOOD AND EROSION PROBLEMS Flooding has posed some minor, but apparently increasing, problems to those ' who live near Big Pipestone Creek in the lower part of the study reach in the vicinity of Whitehall. Flooding potential and ground-water levels have increased to some degree because of partial filling of the channel from , upstream erosion. However, the channel in this area has retained some capacity despite the huge volumes of material that have been transported ' through it. , The most recent flood occurred in May 1981. This flood was somewhat unusual ' for a mountainous area because it was caused almost entirely by rainfall with little or no contribution from snowmelt. Snowpack in the mountains in this area was among the lowest on record, and there was almost no snowpack left when the storm hit on May 21 and 22; however, soils were saturated from previous rain and snowmelt. The major rainstorm centered to the north of the Big Pipestone Creek watershed and produced flood peaks of 100-year frequencies and greater on streams to the north, such as Boulder River, Prickly Pear Creek, and others. Big Pipestone Creek received only about half the rainfall amounts that were experienced in the storm center. From readings taken at weather stations surrounding the Big Pipestone Creek drainage, rainfall over 1 the basin averaged 1 .6 to 1.9 inches over a period of about 24 hours as 1 -10- 1 ' compared with the main storm center which produced rainfall up to 3.5 inches (Reference 7). While escaping major flooding, there was still enough flow to ' cause considerable concern and some flood damages on Big Pipestone Creek. ' There was enough runoff created to cause the emergency spillway to flow 2 or 3 feet deep at Delmoe Lake Dam. This runoff severely eroded the hillside below ' the dam where flows were returned to the channel from the spillway. The flow washed out a 6-foot by 8-foot arch culvert that was at the Smith Ranch ' crossing at cross section AK. (See Appendix A, Flood Hazard Maps) . ' Additional material was eroded out of the straightened section of the channel west of Whitehall. Buildings and houses just above the county road upstream from Montana Highway 55 were flooded. In Whitehall, about six residences along Big Pipestone Creek were flooded or threatened. In addition, two ' residences had basement flooding because of high water tables. The water ' spread to the southeast from Whitehall and ponded against the old Burlington Northern railroad spur fill. From that point, flows found their way to the Jefferson Slough, primarily through the main Big Pipestone Creek channel. ' Results from this study indicate that the 1981 flood was about a 10- to 20-year frequency event. It is not possible to estimate exact frequences without gage data or other flood data over a long period. 1 This study indicates that a 100-year event (a flood expected to be equalled or ' exceeded once every 100 years on average) on Big Pipestone Creek would cause serious erosion damage and some flood damage. The peak flow for a 100-year flood would be about four times as great as that which occurred in 1981. The ' Smith Ranch crossing at cross section AK and the irrigation diversions at cross sections AR and BA are presently holding back the advancement of present ' -11- headcuts will wash out, allowing the headcuts to advance upstream. This , process will add a large volume of sediment to the already eroding stream system. 1 In the upper natural reach above cross section BA, the 100-year flood will spread over the existing brush-covered flood plain. Flood flows in the , channel will be 5 to 7 feet deep with velocities between 3 and 5 feet per second. Flood plain depths will be between 1 foot and 2 feet deep with velocities of about 2 feet per second. Because of the existence of fairly ' healthy bank and flood plain vegetation in the upper area, erosion is expected to be minimal. The flood area will be relatively wide in this area, and the only damage should be to the old county road. For the area between the upper natural reach and Montana Highway 55, which ' contains the deeply eroded, straightened channel reaches and major headcuts, erosion will be the major concern. The vertical bank sections of the ' straightened channel reaches will suffer severe bank erosion during any large flood equal to or greater than the 25-year event. The erosion problem is greatly intensified over what it would be if Big Pipestone Creek were still in its original natural channel. There are several I reasons for this. The first and most obvious is the existence of vertical, raw banks. The second reason is that the straight reaches are now so deep , they have the capacity to carry the entire flood flow. Concentrating the entire discharge in these sections causes velocities to be increased by virtue of the increased depth. Prior to straightening, the original channel would • 1 -12- 1 overtop, pushing excess flows onto the flood plain where they were dispersed over a large area and carried more safely. The third factor is that the straightened sections have steeper channel slopes, which also increases ' velocities. Flow velocities are expected to reach values of 6 or 7 feet per second--far in excess of stable velocities of 3 or 4 feet per second. The ' flow depths for the 100-year flood will be 10 to 12 feet, which is near bankfull for most sections in these reaches. From just above Montana Highway 55 through Whitehall, flooding and deposition will be the concern. The 100-year flood depths will be about 1 foot deeper ' than they were in the 1981 flood. Flooding will extend farther north into the residential area, spreading into most of the first block, which borders the stream. Flood depths will be about 1 foot deep in these areas. (See ' Appendix A, Flood Hazard Maps.) All roads except Montana Highway 55 and U.S. Highway 10 will be overtopped and may wash out. The old Burlington Northern ' railroad spur will also be overtopped. From the railroad down to the Jefferson Slough, flood flows will be split between bankfull flows in the main ' Big Pipestone Creek channel and overflow areas to the southeast. Flow depths in this part of the study reach will be 4 to 6 feet in the channels and about 1 foot or less in the overflow areas. Velocities in the channel sections will ' vary from 1.5 to 5 feet per second. In the overflow areas on the flood plain, velocities will be about 1 .5 feet per second. The tremendous erosion that is expected to occur upstream for a flood of . 25-year and greater magnitude is a factor that adds uncertainty to the ' predicted flood boundaries, depths, and damages. It is impossible to make accurate predictions on the impact this erosion will have on the flood picture 1 ' -13 1 in the lower study reach from Whitehall downstream. No attempt was made to estimate this impact. Flood flows were routed assuming channel capacities that existed at the time the field surveys were conducted for this study. The impact of upstream erosion will probably cause more overflow to the southeast than is currently predicted. After the peak of the flood passes and flows start to recede, large amounts of material can be expected. to be deposited in the channel and on the flood plain in this area. A great deal of reclamation work may be required to restore channel capacity to pre-flood conditions. The flat, irregular nature of the alluvial fan in this lower reach also makes flooding patterns difficult to predict. Flow patterns often vary in such ' areas for similar flood events. This is because of the diverging flow pattern typical of alluvial fans. Minor changes to ditchbanks, roads, fences, debris ' accumulations, and other features can easily change the course of flooding. Therefore, shallow flooding could quite easily occur in areas not identified on the flood maps in this report. ' The 100-year flood is expected to inundate a total of 580 acres in the study , area. This includes about 11 acres of residential area in or near the town of Whitehall. The rest is 298 acres of pasture and hayland and 271 acres of channel, riparian, and brushy habitat. Approximately 51 residences and 2 businesses would be flooded or threatened to some degree within the study limits. Depths of flooding for most existing buildings will seldom exceed 1 foot. (See appendix D, table 4. ) Floods below the 10-year frequency can be expected to stay within-bank and ' cause only minor problems. Floods of the 25-year frequency and above will start causing serious problems. ' -14- 1 ' Description of Information Developed for Present Flood Potential 1. Appendix A contains flood hazard maps showing the limits of the 500-year ' frequency flood, the 100-year frequency flood, and a 100-year floodway. (The concept of a floodway is discussed later in the Flood Plain ' Management Section. ) These maps show the location of all cross sections listed in the tables in appendix D. Location of survey bench marks is also shown. The maps give a good visual display of the extent of the area subject to flooding. ' However, because of limitations of the extent of the survey data, certain areas subject to flooding may not have been included or vice versa. The ' actual surveyed elevation of any point in question should be compared with the computed flood elevation at that point to determine exact flood hazard (see appendices B and 0) . Flood elevations were computed assuming that main channels and bridges ' are not blocked by debris or ice. These conditions can increase flood 111 elevations over those computed. 2. Appendix B contains flood profile sheets showing profiles of the channel bottom and the 10-, 50-, 100-, and 500-year flood elevations. These profiles were prepared for the main channel only. The cross sections shown on the profiles correspond to those shown on the ' flood hazard maps in appendix A. These profiles can be used to estimate the actual elevation of flooding at any point along the channel. ' -15- 3. Appendix C, Selected Cross Sections, contains plots of selected cross ' sections that show size and shape of typical channel sections for the various channel reaches. 1 4. Appendix D contains several tabulations of data. 1 Table 1 shows peak discharges for the 10-, 50-, 100- , and 500-year flood frequencies developed for this study at selected points. Table 2 lists the elevations of the 10-, 50-, 100-, and 500-year floods for all cross section locations. These correspond to the elevations , shown on the flood profiles in appendix B. Table 3 gives information relative to floodway widths. The table gives the widths of flooding remaining if the flood plain were confined or encroached upon from both sides so as to raise the water surface 0.5 foot and 1.0 foot. These are theoretical values computed by a computer program. The 0.5-foot increased depth floodway is the floodway defined by Montana law. This is shown on the flood hazard maps. Seethe Flood Plain Management Section for an explanation of the floodway concept. Table 4 shows the number of acres and buildings flooded for the study reaches. 5. Appendix E, Elevation Reference Marks, is a list of survey bench marks and descriptions. These are referenced to the reference marks shown on the maps in appendix A. -16- 6. Appendix F, Investigation and Analyses, discusses the technical aspects of how the study was done and the data sources used. 7 . Appendix G is a glossary of terms. 8. Appendix H is a bibliography. 9 . Appendix I is a legal reference--a copy of the Montana Floodway Management and Regulation Act. 1 FLOOD PLAIN MANAGEMENT Existing Measures and Programs ' The Town of Whitehall has been in the Emergency Phase of the National Flood Insurance Program since May 2, 1975. Jefferson County also entered into the ' emergency phase of this program on June 3, 1981 . This program is administered by the Federal Emergency Management Agency. Flood insurance is available at subsidized rates to owners and occupiers of all buildings and mobile homes and their contents in Whitehall and throughout Jefferson County. It is recommended that owners of buildings and mobile homes within or adjacent to ' the delineated flood hazard area carry flood insurance on the structure and its contents. i ' Structural Alternatives - Flood Prevention The flooding problem in Whitehall could be eliminated or reduced using several ' approaches. These could include any of the following: ' -17- 1 1. Levee on south edge of Whitehall. A low dike or levee about 3 or 4 feet high could be constructed along the north bank of Big Pipestone Creek, as needed, from Montana Highway 55 down to Brook Street. From Brook Street, the dike could then follow Lucille Street down to Division Street. This would prevent flooding from the 100-year and smaller events in Whitehall; however, provisions would have to be made for drainage of runoff from the area between , the Burlington Northern railroad to the north and the dike. This alternative would not change the flooding potential for those areas outside Whitehall city limits. This alternative may be economically feasible if coupled with street improvement. 2. Flood diversion and floodway. A flood diversion could be constructed on Big Pipestone Creek just below Montana Highway 55 to divert ' excessive flood flows into a floodway on the south side. The floodway could be constructed to carry excess flows from floods of 10-year and greater frequency to the southeast across the alluvial fan and through the county road to the Jefferson Slough. This alternative would offer flood protection to all existing development below Montana Highway 55; however, it does not appear ' economically feasible based on analyses performed during this study. 3. Channel improvement and maintenance. The present Big Pipestone channel could be improved by removing snags, debris, and other obstructions . This alternative has been implemented to some degree and has had some success. ' Keeping the channel open and as clean as possible will also allow for better sediment transport through this reach. This alternative would be reasonably effective for floods less than the 25-year event. It is probably the most practical and has the best economical feasibility. -18- 1 ' Structural Alternatives - Erosion Control While the above-listed alternatives would reduce flooding, there is no ' guaranteed determination of how their performance would be affected by the ' large volume of sediment from the erosion of the upstream reach. It is recognized that, because of granitic sands in the watershed, Big Pipestone has ' always had a certain amount of sediment transport. However, the presence of headcuts and deep, vertical bank sections makes large amounts of erosion ' likely during large flood events. Several alternatives were investigated to determine ways to maintain the location of existing headcuts and to reduce bank erosion. These are discussed below. 1 1. Concrete drop structures and channel bank protection. This ' alternative would control the 100-year and smaller flood flows within the ' present channel alignment. Three large concrete drop structures would be constructed at the three existing headcuts at cross sections BA, AR, and AK to ' prevent further upstream movement. (See Appendix A, Flood Hazard Maps. ) In addition, the existing vertical bank channel sections would be shaped, revegetated, and riprapped as needed. The cost of this alternative is estimated to be more than $600,000. This would not be justified based on the apparent low number of benefits received. 1 2. Concrete drop structures and floodway. This alternative would ' include three moderate-sized drop structures with the drop structure at the ' irrigation diversion on State land at cross section AR also acting as a flood diversion structure. This structure would divert excessive flows from floods ' up to the 100-year event into the old original channel area, which would act as a floodway. A dike would be added to keep the excessive flows in the 1 ' -19- 1 original channel area until it rejoins the present channel just west of Montana Highway 55 at cross section AD. This alternative would be designed to limit flows in the present deep, vertical bank channel sections to values that would keep erosion to a minimum. The cost of this alternative would be more than $300,000 and would probably not be economically justifiable. A less expensive option under this same concept would be to construct just one concrete drop structure at the irrigation diversion site (cross section AR) . ' It would still act as a flood diversion structure and divert excess flows into the old channel area. The difference is that the other headcuts would be , maintained as they are now. This would be possible because they would be protected from high flows by the existence of the new concrete structure. This structure, with the dike needed to keep excess flows in the old channel ' area down to cross section AD, is estimated to cost about $160,000. 1 3. Rock chute drop structure and improvement of Smith Crossing. This alternative would replace the irrigation diversion on State land (cross section AR) with a rock chute drop. Additional rock riprap would be added to the Smith Ranch culvert crossing at cross section AK to protect it from washing out. An additional culvert drop with rock riprap may be added between t the above-mentioned structures to reduce the present channel grade between ' them. The estimated cost of rock riprap and its placement is about $200,000. This alternative will not prevent bank erosion from large floods, but it may serve to prevent progression of the headcuts and the erosion from that source. Considerable maintenance would probably be needed as it is expected that these , structures would be damaged to some degree during,floods larger than the 10-year event. This alternative appears to be impractical from the viewpoint of limited benefits downstream. -20- 1 ' Nonstructural Alternatives The citizens of Jefferson County and the town of Whitehall have several nonstructural flood plain management alternatives they can employ to reduce ' present and future flood damages. A sound program can be developed with implementation of sensible landuse regulations using provisions in the Montana Flood Plain Law (appendix I) . The law is structured around the concept of floodway and flood fringe areas within the 100-year flood plain. It is ' appropriate to discuss these terms to better understand how various flood plain management options may be employed. The concept of a floodway was devised because encroachments on flood plain areas with buildings and landfills will increase flood depths and damage to existing property in the vicinity of the encroachment. A floodway is defined as an area within the existing 100-year flood plain where floodwater could be restricted while limiting the increase in flood depths to some specified value. In other words, the floodway boundary at any tpoint is computed by assuming that there are walls or dikes on each side of the flood plain which can contain the entire flood flow between them. As these walls are squeezed together, the water surface is forced to rise by some ' amount. A computer program is used to compute how much these "walls" must be moved together to achieve a specified rise in the water surface. The computed ' location of these "walls" defines the floodway boundaries. The specified rise by Montana law (appendix I) is one-half (.5) foot for the 100-year flood. The ' area between the actual 100-year flood plain boundaries and the floodway ' boundaries is called the flood fringe area. (See Isometric View of Flood Hazard Areas on next page. ) Montana law officially refers to the two areas as ' the designated floodway and the flood plain fringe. -21- 1 1 Basically, Montana law provides for many landuses as being compatible with , periodic flooding and they are permitted in the designated floodway. Some of these uses include agricultural uses, industrial and commercial loading or parking areas, and open-type recreation areas. Buildings for living purposes , or commercial structures are not allowed in the designated floodway. However, buildings are allowed in the flood plain fringe areas if their lowest floor elevation is 2 feet above the 100-year flood elevation. (See appendix I, figure 1. ) Flood plain management options within the framework of Montana law could include, as an example, the following items: , 1. Individual levees or dikes. These measures may be feasible for some ' properties in the flood plain fringe zones. To be effective, they must be properly designed and constructed to prevent underseepage and embankment failure. 2. Elevated pads and fills. On an individual basis for new construction, this is probably the most foolproof and effective method of floodproofing. (See appendix I, figure 1. ) 1 3. Floodproofing. For existing structures , practices such as raising foundations, installing watertight seals on doors and windows, ' eliminating low openings, installing valves on sewer lines to prevent backup, and installing sump pumps could be considered. Constructing small masonry walls around residences with openings that can be sealed is also a possibility. (See appendix I, figure 2. ) 1 -22- Ma a i n a la OM all a a al a a I= a a a a a PREVIOUS FLOOD PLAIN FRINGE WITH ALLOWABLE J ENCROACHMENT .# ON FILL ; .4% f • a �,,- , �,,, `mod% {,°`f r.: a,� ,.y�• �,p,L 4 ,5 / 1 [ 4. ...:-.-.. .4 4 @ �,f/�Fe' ;et ci, ■ <,,, T / J✓ • �,�Lh 4 p r. 1 ,.,‘14.,,, (J / :;: / .. ••••••••••••••1:•;•.•'?.••••••••■••:•'.:• 4"Vf 4. %.,"*" •••.11::•••••••:•••••• / et ','l y.a'k..., : 3b3 1n` ,.:k f. / ..............-..........--...-........c.7.s- _re,- ,-;:,..1:Sser'::::::ilirt:::1:::::::::;;;I: / Visal:- . lie r7, r, Ay,„.,, r• ' , � •:::::::::::•::: •a . � n. SURCHARGE . .� ik, �.c�' -•++_+.mow y. r :'�.Y rl� _ .�x� �� �p T Ty ^'. y T�.f _A -S• a; s a - r Ili iii F- o%� 7j. ISOMETRIC VIEW OF FLOOD PLAIN FRINGE FLOODWAY FLOOD PLAIN FRINGE FLOOD HAZARD AREAS 100 YEAR FLOOD PLAIN - _ 1 ' 4. Flood insurance. Federally subsidized flood insurance is available through the Federal Emergency Management Agency (FEMA) and is sold by local agents in communities and counties that are participating in the ' flood insurance program. While insurance does not stop flooding, it covers the costs of flood damages to property. Flood insurance will pay for damage caused by high ground-water tables if the rise in the ground-water elevation is directly related to a natural flood event. 1 5. Relocation. It may be advisable to consider relocation of certain buildings or dwellings that are subject to frequent flooding. Under the FEMA Flood Insurance Program, relocation assistance is possible. 6. Flood warning. Provide a means of warning those who may be flooded during rainfall or snowmelt events with enough time to move belongings away from danger of flooding. The National Weather Service provides flood forecasts and assistance with local warning systems. ' 7. Flood plain zoning. Develop regulations that limit future development and encroachments in flood-prone areas. This is a very sensible approach that works with--rather than against--nature. 8. Debris control. Measures should be considered to minimize the amount of ' trash and debris that is deposited on the flood plain. Besides being unsightly, trash and debris contribute to water pollution and offer ' potential obstruction to bridges and culverts. Snag and debris removal ' should be an ongoing maintenance item in the lower channel reach near Whitehall. -23- 9. Maintenance and improvement of riparian vegetation. Because of the importance of erosion control, vegetation along the channel should be maintained and improved whenever possible. This vegetation is critical in helping to reduce streambank erosion and maintaining stream channel t stability. Vegetation will not be very effective in the straightened and vertical bank sections; however, vegetation also improves water quality and provides wildlife habitat and scenic value. ' 1 1 1 i 1 1 1 i 1 1 1 -24- APPENDIX A 1 MAP INDEX ' AND FLOOD HAZARD MAPS 1 1 1 i i 0 1 et c,) Izd co 21 22 23 24 19 20 21 22��- 23 24 19 F / ' ••■••■ Ilk C.- 7 90 '-$ 6 25 30 29 27 26 25 30 411141 c^ N P, 4L,p'y -------------_ ,Iliiiiiiiiii! OM1 33 4.' � 31 i 34 35 36 31 Pipestone ~ � w� . 2 N. 3 pilliy ..------ so, - .. ." .. 1. 1. 1,..... ftliiiriZ vf•�t"�_�_� 2 14°° 4 IrliFFP". 2 1 6 CANAL 5 / �4 ;IP 3 BURL INC.ppAt 6 r,e `.9 ��o.` f zi4o Q AIL t r- 1' ❑ ►► 1' r _ \,_,,,,E, Little 9 10 11 12 7 '_, $ 9 a— h' 11 Crzzh V 12 47 1 / 7 Q =�._ G ' Frsh �� e" � �� PHOTO INDEX MAP / Wr' BIG PIPESTONE CREEK e° FLOOD PLAIN MANAGEMENT STUDY I3 PHOTOMAP AND NUMBER �I� 13 18 X - / JEFFERSON COUNTY, MONTANA V pr 16 15 APPROXIMATE SCALE: 1 INCH=3200 FEET 4 ML WNSe TNIfN xiwice X -- o®U9 OEPARTMCNT Or A0111C1,I�TL scs.ro.r.__ _ lass MT-N-8500 �{ tiT " '0;" .;.- t < � x f„` LEGEND � 1 f --7-i- — � 4"'e--L. ” �i 4'. y 00 Year Flood Plain h • `uly j � $• N.,- . r z ` I 1 100 Year Flood Plain < ? 7a i x. 100 Year Floodway Area•,a k i fi y .aF ✓ ... -_ t �� ,. -.4..r 1�. p�. Y . r' s x fp_! T (4351.2) 100 Year Flood Elevations v ✓ ',\'' ' Valley Cross Section and Symbol \ ' . •,..,...;::-. 9 Section corner and Number s RM-6 Reference Mark and Number • A.'. ,w .` -- A 500 0 500 1000 scale feet t d' r � ► • \ ea 1- t J74:t.- -., yam, ; * = PHOTOMAP 1 = x, ' : , , , �, y s FLOOD HAZARD PHOTOMAP BIG PIPESTONE CREEK a . ; � .> 'ice FLOOD PLAIN MANAGEMENT STUDY .4., _ , . T- #' .. . JEFFERSON COUNTY, MONTANA {! z. ..,.y, =, ;'' * ?' 't` :► 1979 AERIAL PHOTOGRAPHY ` v `fw. aa.}l 'v. 'r . � r" ter _ s �.' -,�,: �Tty,� m ,` � - _ O 501E CONSERVATION SERVICE '' s � ?� `! . y ,a ' t .g `.f U.S. DEPARTMENT OF AGRICULTURE MT-N-85002-1 . ......,.• „,,,,„,_ .. . - tPr,' -4,, .... .e. 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"•• '•.'••-••.• '• t'-' ' •-it". ■ . ; ; .. ;IP:, •7-.:... . • •',i ' .1. ••''' • ::: 4.,: - • .%• - . 410 .k. • , . ., . ,..1,1,..• ',., . • ' .. .-• , .. • , .',.,.:-::7,•,...y . , :. . ....„1 ,. .`if;:;1..:;:o. :'••••''',,.'..., 'J.* '. -4';:.....r. • ' ' ' -....'..'-'";':::a-',.:,..-'1,.,r;,- . ''.... '', - •- —- -. • ' . -.. II -.• ;... (,-tl':'''''.- ...;.;;•1.'"..:•‘k..4-.14.. • • ... . ,•-• . .. ... ,,.. .. ' ,fk • . l' . - LEGEND - 2,-",3---3- r 'e , ,( 2 K• Sj, 500 Year Flood Plain • ¢ A `N• T 1 N• s- Q W" 100 Year Flood Plain ,. 1, L I 100 Year Floodway Area 1 fl . `R 1:1 4336.9J 100 Year Flood Elevations ©RM-5 I AE� Aj _97/0 _ © Valley Cross Section and Symbol N HEH,,r I RAILROAD _-_- _ r ----, ," — r r 31 Section Corner and um er v • �. `'' ` 1 ^I` AF -" Reference Mark and Number Big �1^ -- t' —== . ti , -- ., '''.. -, ,,,to N4 i • 4. , 006i , 0 / iri . n. =fir\. t..1 w-tl.. / e .% ' _.; y 500 0 500 1000 a scale feet co p r t rr ?,'''' as t t 1 t ' r ti. 4041" - * ' y, KE ! !ti'" 1 t t r 4 r :, r ;1,A.. 'j. el y t k PHOTOMAP 2 •i,• , d ti% R ,� x • � LOOD HAZARD PHOTOMAP t , r� > A'. BIG PIPESTONE CREEK ¢gin , " �,- ` FLOOD PLAIN MANAGEMENT STUDY ■,... ' ` JEFFERSON COUNTY, MONTANA r y ' V 1979 AERIAL PHOTOGRAPHY '.� / ,z r 1 t i. 0 SOU, CONSERVATION SERVICE v US. DEPARTMENT OF AGRICULTURE MT-N-85002-2 3 A r W t ?i 5 A R• 4 �•+ �• 1 k, I. Y 4 `E AD 4 I______L R 0 A L______) .,,,,,,,.:_____________ ---- A estan U. RLI Pipes R. � TM 5 T '- !r v, '''5'''5"- '3 / i d . v ~^ s fiako j } • � '' " $ — J ,' ., x a5 i may m x ;4 _.y :r x , .,• .r, ..,y; _ a:y f.+.,...a I':,`,$. '" 4,M'... .. h iF 4 � y ry kc * t y % fi L S f - " �Q � � ' �, It, \YI KY 1 14 '^e ,e�,. - .r _., TSs y_ �a `-hae ; 't.4k - T ;.: ti y`d a k' o ,. - ,y„�'. ,# �$ s ' n'r'a .rk .�.. r y.,• i^ " fi ' a a . k I + 1/ A • . .-. - 'V LEGEND . 500 Year Flood Plain I 100 Year Flood Plain ?" ,«a Y• a ; �: 1 100 Year Floodway Area i /t r 4 (4421.4) 100 Year Flood Elevations 1. �'� O Valley Cross Section and Symbol a V S t , t - . Y Y + 35 Section Corner and Number y b ri Ir { .a, w AT s r ?4n p r , C., / R _3 QRM-3 Reference Mark and Number•It TON , RM" Y I f y. • NORTHERf! kt a RadIl140s,O »: ".TM , °t a :; `may hi ft wf 4.1:',72:„•,.`..,7i'.4� ; ..I �g� r• { r''''''''''PL 4` f a l H r ear n' i t ;nc*-t rhRk 500 0 500 X000 f �.�lf. " i°* m r� � ` w �r 4 G s r f a` s — fJ SC81@ f @ @t a•w. k.. a i � ; � , R L J 1 2 S 4.y a,t-ij O • 531 r` •' ; N. 3 + -: • �, 1 M`' �?� �P �? , 4r • I - j PHOTOMAP 3 . r FLOOD HAZARD PHOTOMAP • BIG PIPESTONE CREEK • .,� FLOOD PLAIN MANAGEMENT STUDY JEFFERSON COUNTY, MONTANA 1979 AERIAL PHOTOGRAPHY I f ^ �(�p SOIL CONSERVATION SERVICE U.S. OEPARTMENT OF ASF,ICULTURE MT-N-85002-3 x 1 F 'Q '` s•• } m I a f {� QRM- ® RM Ar C NORTHEAN 5 A'AILAOHD BURLNUQTON O ;I i t. , .r.''."'='''',,.• :lif.'',,. . . ,,-• ,--, . .• .' ., '41.474,:',' i CD, ., '.. UOni BB Pipestone i � f, ti ,, A ' .. . •-a e ..., ---Th ...lig ,,..„ . ,,_ • Ar.' ..V .. . .. , t >,t',., / I. .:..0, - �„�.,,...^+-"""rte )Q 2 1 w L.,-,re!, ‘ . ...1 . . 1 1 • APPENDIX B 1 1 FLOOD PROFILE SHEETS 1 1 1 1 1 1 1 1 1 1 1 1 1 r 1- -. a n 1 M t _ 4365 cc i 0 rn E c , - y-. 4360 -0 `s 1 g. o �. 3 Z ��,, - 0 >: m - W '4 I/ 0 gg 2 - / a r1 © 4$55 _ - 4-355 1 0 (0 ' �' �-- _ I 1 115 -Oft , [ I t 1 APPROX FATE CHANNEL BOTTOM.-. ' I r 1-. 1 - J ¢ } �� / , 4350 m 0+06 , I Q j 8, / "� 4•. HgNNEL STATIONS 'IT, , `, I f I � 1-` .11 ls T. r_ . C 75}bRF � 11 I I I I , I' I -I . j L IL tl// LI _ -� ' t T , rI_ _ MiANMEL S AT10N$ I I I h'` AF�PROXIMATE CHANNEL BOTTOM r rte- ` 1 r BIG PIPESTONE CREEK -,r- 4,..,„ 25-00 1 valley Section WATER SURFACE PROFILES and Symbol 0 0 0 *a 600 year ' - . BIG PIPESTONE CREEK Bottom of ..`of Deck Top of Calvert •`1O year FLOOD PLAIN MANAGEMENT STUDY j $GALE Culvert JEFFERSON COUNTY, MONTANA Horizontal: 1 inch=500' feet channel Bottom of Deck I _Verficapc. _1 inch=5. feet ' - Bottom CULVERT/ / BRIDGE PROFILE SHEET LEGEND O U& MTMt cr. fl C 1 OF 4 MT-N-85003-1 I I ' 1 I 4365 4364 V I - --/ --4360 0 �" —� ' 4360 � 0 ,_, — o 0 i i� - ., ■ -4355 i — 4355 , ■ _ . - CI I , i I APpRO TE CHANNEL 8 "' _ - I � 1 of / I l al I +- , 4359 y� � I IQNS ADO+O 1 aHANNE, $'TAT I 1 I----.4345---- , g 75}00 � I 1 � ! 1 I r l- ILI 1:.J , I 1 Ti 1 , w o 4349 L� _ { O . c G ��� a 4335 a. '; .i cS Off` ���. m r"'%✓��� HANNEL St ATIONS F mss---` .A PPDXµ}A`TE O�IANNEL BOtT*M I I 4339 - 1 '. a,._ I V��/ ■�/• /� 0 I Valley Cross Section WK e and Symbol FLOOD I ELEVATIONS. 4325 a5�o' 0 0 O `LE500 year ._j 0+00 Top or Road _ too rear wee rear FL00 GALE Top of Culvert— — �10 year • . . I '$ Bottom of ToP of Deck JEF Horizonte. 1 Inch=500 feet Culvert Bottom of Deck Channel Yertic.n�c a.inot=�& feet Bottom v -�� BRIDGE`- ' CULVERT BR LEGEND O s L o I i I f 1 • j - rr � t '= 1 ; i 395 1 � : i 1 r t , 1 l � t I 1 I , ' l . [ ..lr Iti. . II I , � 1 I I r 4 I r I J . I L~ II .. IF 1 . '- . , 1C`_ -1 I t- 1- l ' . 1 ' I Jy ' 1 '' 1- f� Y4__11-" 11 '� ] 1 � in : 111 � I -V--1-1-1-E I , I- Il i , rr to F {-�r - 1 L i,/� / X3$0 li I t I 'I tr in }I11tttttl II t� * it'-Yt 1 � .' Ll Li -i rl '�F ' i . L I..- ' 4r 4 `'e! rr'7 ' Y� {— 4 ` _ tll r '. 1 I I 11 ' 1{ 1 f� _i. ' i f 1 , ' rl L i .,/ • 1p 11 i J , I , r t I t 1.4.1._ F H { --r 1: 1 r 7 11 t ' • -- , i I I r- + , Jr ( I it . `'t f _ I rkl l f ' r_f4 _4- _I- f tt'[44.1 ' y'! I . j t ' t , `� ' F- r }- �- - 4j I t , r _t .+._i_.i ' 1 `1I 1 1 I 11 _ ,,-,]-1--C4-..F 1 1 r-, +t , I I I -,'�1 t ' r+t.-1 _ ` t` __ , r. . l 1 t - +1 �Lr _.:i_ r� -'_.!+:_i 7 -1 ��r� 44-� r' 1-. '-i 11 r J�'r' J/) 111 4. }t 1 1 1 t r t I L� !:.' I ` t { 1 1 I r) 4-IL r- [ . , I -tr _ :, .�... ,—i I t � 1_1 -, J. '1 I 1 �--�� 1 -r E 1 �ry� I - j t j-' ICI -,,-� . IL . I ' J �. } ��._. .r - .8Q y ;_ II it I 1+ i '�� 1 fll,- ' ` I , ;.. � - , ' - ....1,-,▪ i . � rl"`� - I+ I , } I _ ., � �. i � I � � � r � I I I , 1- _ � _� � �1 I L -F- I 1 f - 1'r f i 1 { L i__ -,--r -I _ F r J { 4 ▪ ,-' 1 i I� sz �y � rt + -,i-� -_ 1 . ` f ' 1 +�C I i- II , , , L H f 1 1 t'y�r �--1 { `Y., t �_I_ t t '...,1 1 1 -{ { • t ` • + .le 75J t c� it , , If, f II l . . r 1 0 OQ 's � e 1 11 }_ —��I 111 . 1 I' v✓ I . . ., 1 . t . , 1 [ 7 .r 1 . ,� f - . ___— I � ^ I r I 1 • ' 175-m�J, I I . _I` , , 1 f . 'APP 6 4ATE C ANNEL BOTTO ; I I-- r r I II Lit., j. --------- I 1 I 1 I I•` I sir.°✓i III I I _ { r o✓�.o�� i ,sq ©b I .;. -1 1 -1- ' OHANNEI4SThTIONS , ` BIG PIPESTONE CREEK I , i Valley Dross section i WATER SURFACE PROFILES• , . and Symbol FLOOD ' 12s+oo } 0 ELEVATNS: I BIG PIPESTONE CREEK Top of Road —+ 700 year I : SCALE Top of Culvert year • FLOOD PLAIN MANAGEMENT STUDY Bottom lv rt Top of Deck JEFFERSON COUNTY, MONTANA Horizorlta': 1 Inch=500 feet Channel Bottom of Deck Bottom �� r -. Vertical: IDCh=a~. feet CULVERT BRIDGE • /� �,� ,rwt,a, PROFILE SHEET LEGEND y ua � rn v earence .e wuune 2 OF 4 MT-N-88003-2 I + I { I ! r . I - , i 1 I ' F f 11F . r I 11 I 'i - � f 1 ' .' 1 � ..' I � . 1111 It : F 1 I it 1 . t : 1 AEI- [ I . 1 f Y r 4 L r l 1 r I 1 tI ;! + , t is Ir 1 -r ' rI 1: : ; ;-; - ,, Cr. Cr 'Yr f Yt 1 rr I , ..- f r h " 1 ,j- -.i' r 1 flat 111 tt I r t 1 IT t1 , 1 , 1r ' I k;H , I- . ' 1 . Li-i-_t 1 � ■ 11 1 1 t I '. 1 r , 1 1 , r I ' 11 ! 1i I I I G' ' r r 1 I _ Yr +_ t: L r 1 ■� I r1. , -- " + ` t�T -- ' 1... i J --"---11--/; _.,. I .. t,1 4 ..L:: rt 1-1 .1i Ir t 1� !� IJ • t. 11 1, _hill' >, }1 ,-1-41 j { ,p .- - l T`I r , , 1 Y-- ' � �4 t .4 ..--;--,--f-;-.1--y -' Y ; ;. I T' i.,- : , j:-.� �l �- r � I. ! f '- [1 H. _jilt? T 1� Jam_`}L 1 I -r° S.a _: _ I F_ _1 r-- -t tt rr r � . •. I : . I '-Y rr�`- ,--, J. �...JI.II ■` r1�..4 - � 1 r1:. 11 h Ft ! ..I�}° � + ! 1�1i1 , t k rr, 1 ; -I { ! 1 I !1 I I J•W ! I ' 1 - LT' ��" r :- - F 1 1 .' ..I- t i 1�t-1_ 1 $-r t _j �T ' i , : r".?- 1. .. ;. 1 1 I II-•' 11 � t i- ,• - I - '.j -k,- _. {-1 ,l Ali. / �yL.�- F I f,n I i i. S ` r " L. 1 r , 1•i 1 + L 1 1 -r{ 11 T• 11 1 } { I 1 y .-r 1 1 t a-- -L 4- `` 1 1 (--1-'-1-1-4--,t-°`'L 41 , t + 1�T'LI 4079 - 01"1 1tr ,_ t,- T I 1 :-f 1 11 : 1 'f , tt j Y 1 .r 1 • �' _ f� / ' �� �� A8 ham. �/ mil/ / 0 4-370 v/• o 1-1 I - . 1 4 1 _ --�' ` • tT5=4A p • 4 — ,OR % 7- 1 APPPO$IMATE CHAt NIEL a9rTo 1 4366 1 , — _l t � ' r � s� ! , I . i I " r / tsot© . I .f// ---I 4360 - I 1- i i s L�arivr1orts L . � i I Iri Venev Craea Section 1 t and symbol FLOOD 1 i 1254-00 . O O O ELEVATIONS: ._ _ _ _ ; -_ _ I ( � 600 year 4355 I Top of Road —.—too year Top of Culvert 60 year F 115+00 1 I f SCALE '`,D Deck t Bottom of Top of Deck I : Horizonta': 1 Inch=5,00 feet Culvert =ottom of Deck Channel 1 • v Bottom _-. _ _. . _. •.,.. I. V @rilCe�: ipoh 5, feet CULVERT BRIDGE LEGEND O -. ._.1_ 4420 P O I — ! ® / 4415 I I ! 9 ,' I V 1 , ' 4 ---------I pmj I ' .�/� ''J �,�f/// 4,410 2 I' [ _ .L 1 { ; t 'MI -�' _I _ I I - - i I .–�"'/, ,_1 , i , , �. t' I I II � i 1 F ' ` f - I -'1 Tl J I i t �� U r f - i Ad I I,=�,y-,--�' ����'� I 4405 ff ' CAI –_—rte _ ;__ I,.�, i T re Z I I 7 .- 265{00 I- 1 Y IC I .rfl 4400 'q J� - II 4e/� i= ________.-.-1-_ �i ' I I :��l4ll 1 4 1 —t-- { . ✓i i , °'f 1// 250+00 ��, I / . t —1-- : I I 1 APPROXIMATE CHANNEL BOTTOM j . I I i i ' ��. . I � –1 — I- 1i 225+00 . CHANNEL STATIONS BIG PIPESTONE CREEK . r�I/�. // - .... Valley Cross Section /�"'`�� ' Symbol 0 p 0 ELEVATIONS. WATER SURFACE PROFILES -- - 600 Year - BIG PIPESTONE CREEK Top of Road —am...100 Year 80 Year FLOOD PLAIN MANAGEMENT STUDY 1 Top of Culvert - —....."".10 Year SCALE Bottom of Top of Deck JEFFERSON COUNTY, MONTANA 200+00 I i Horizonta$: 1 inch-560 feet Channel Vert Bottom of Deck f _ 1 _ -�. 1Lartiaal:- I inch=51teet Bottom CULVERT / BRIDGE I PROFILE SHEET I eac axmoT�ATaN eem.ce LEGEND y ua oerraTMENT or uTOUVUaa 3 OF 4 MT-N-88003-3 r , , , i , . r . . : : . r Valley Cross Section 1 WATER SURFACE PROFILES 500 year BIG PIPESTONE CREEK _.— 50 year , FLOOD PLAIN MANAGEMENT STUDY ' Bottom of Top of Deck JEFFERSON COUNTY, MONTANA Culvert ' , . ' ' ' ' 1 Horizonte!: 1 Inch=spo feet Channel Bottom of Deck 7 • Bottom . .___,. __. , VatTLIbai: 1 inch—S'feet : CULVERT BRIDGE PROFILE SHEET mr-w-e6003-+ 1 , - I . , , , j ; ■ 1 , 1 I _ I I.• I 1 1II ¢ 1 14 L 1I w I 1—f ,— . . I F I -f 1 l I 1 J 'n T i ' t 1 I , �.._1 0�� ' + f- ` I .� I r } - L - - +I r , t F 1 { t r— _ . r r h F t + , f I.n- i' - f 1 I I I + t � F f _ _ f I 'S{+rt-- I4L+ r` fl 4 r,.` 1 r t- T+ —1.--.; i 1 F jI, r t Sri L j.1 + _1� vj1-rt y++..+,. ' _. . _ tI Ii-' 1 '$ ' 11 - 1 ^� i ✓ - a' I ::�t i . i ` 4. . . 1_„ , . . . t .4 ' I J ,, ! ■ i. a� r+� i-� I ri hi__ �fTI 1 j r lde -IiF f � t . : r C 1 ' r f r I -1 rf p I ' I r7 Its I r/�rc 1 r f v+/�. t 1i r _ Lt T; tL4 t1 �•Y >fiT1� ` r I . � • ! I C 4„-_-7 t +� I I I ! -� ♦- r I I F • �Cr i II I 32.5 p O:� H I �' -t 1 yr_ �f ...:�� rr r I: 11 ! r /y, y/ r II �, r � A II- 1 . ., ,, r } : I h l 1 it ' t . I {1A.� . �,,�+ fi I � I 1 : r 1. 'M - +tom- rill LL F F I I `+ ■ �,.,✓ APP.KQ7 INAY$ GHAn-- eQTY6M• I 14 y 1 —I .r I t .I Y ' ' I ti 1 /•/i; IF I Ii I I /I , : : : . i 1• 11 . I { g , J� �1f/CNhIE}� ^aTAh'IO�V / i I j t P H 1 Valle Cross Section 1 I BIG end Valley Symbol WATER 1 FLOOD t O 0 0 ELEVATIONS: BIG __- _ - 1 600 Yeer I , Top of Road _��SOO year•2�5-00 Tp 60 year FLOOD PL/ P of Culvert ~`10 year SCALE Bottom of J Top of Deck JEFFERS 1 Culvert Bottom of Deck I - rizonte?: 1 inch=6QO feet Channel �_I —,-_. H 1fectl�aL 1 IGCh-6 f§flti. Bottom � � � 44O5 CULVERT BRIDGE 1 .2q6 00 ' SOIL cMaamnwx LEGEND O ua oaaalMSNT 1 i ' APPENDIX C 1 ' SELECTED CROSS SECTIONS 1 1 1 i 1 1 i 1 1 .- ammo- fi 4+00 .4•.• 8+00 12+00 16+00 20t00 24{0Q • 28-00 8 Cross Section "D" (main channel) C s'Section "DD" [overflow iom are l I , I 1 I I I I TT : -- [OS ' Q f i� Y 1 Y � it 12+00 4+00 8+00 T ^ t t 00 1 28 00 Cross Se ta0n "(� 00 t6 00 20 00 �4— --T u Fi II I , f . I 1 j • i ! et { _ 1 Horizontal I ihch=24 feet ! � r - . 4 Yert(ce 1 inch-5 e0i 460 BIG PIPESTONE CREEK •: : fi ... . .: : TYPICAL CROSS SECTIONS 1 CENTER LINE •S•-• OF CHANNEL�.,I j BIG PIPESTONE CREEK FLOOD PLAIN MANAGEMENT STUDY 600 year "f"' "';: :-:::::::::•:::,:. 4+00 8+00 12+00 60 year JEFFERSON COUNTY, MONTANA 1 ' 161- '•• � FLOOD ELEVATIONS l I GROUND LINE ' 70 year Cron$ Section."0 -1-------' 1- - [1 LEGEN6� SOIL mNSCRa,WN aemmCa D L A.ua OlRNrTN[NT Cr I43%1QSTUNa SHEET 1 OF S MT-tl-86004-I I 4340 4,-4.:::::::::.:::4::4::44‘::4:-::•:-:...74.--.4.4• .... I 4335 I 0+00 4+00 ..% 8+00 12+00 16+00 2000 24+00 Cross Section "D" (main channel) Eioss Section "DO" [Qierirlohr irp 1 1 4, 1 I . ,LI Ei , l , tl ici 1111 , II , . I � a I I l . L_ , . I �. I 4355 ? I ' � T t,. . I 1 0 r >D r J k ..,. a 4 4850 jp, .., ... ......• I I cl 0+ +00 • 12 0Q 16+0 20 00 1 24-0Q 00 4+00 8 { Q Cress Sullen O j W I " J I I 1 1 1 f I S�0i4LE:- }_ _ I Norizoht8� t ihch=`2Ub'teet' . 1 Vertical 1 inch-5 feet - 4360 4360 I BIG PI ,„ . ••• CENTER LINE I TYPICAL 1 t .:i. --,4, . :;:- .r OF CHANNEL I • 4355 °7 BIG P I FLOOD PLAI r :'•600 year JEFFERSO +00 4+00 8+00 12+00 16t ` ' so yea year ♦ pp OROUND LINE ' 10 year Cross N I "'• '..' FLOOD ELEVATIONS Section I LEGEND �� a } I 1 Cr ss Section ` B" I � S " D" �,1 1 I Ctoss ectiep A 1 T } • r - f--r -, t .r.,,::::,-.17::.:::•••••••• T' ' r _ d r �r' , -1- •r � y ___ y r `y. +.- t _ „ 1 . T-r � - r ..,,L� +....: L ..... ` ' ' 43�fJ 1 I , ( a�Qp { . ; � "_-- ,1-$�'-Qn _ .� I L❑ .—Y 1 [ f41D_ I 19 , 1 _:� '., . y, :k. 1{ f .. 'F-t `Lir�C k 44 I.{' { . 1 t� '�� ' 4 ' I� li-, L ���� i.11 ; -. ; 1 - ' .— . r rI 1 I =■ f h 4fl r x I y iT r '..� 4 Ii , I I , r I Q Q I t i • r r _-f I I I 1tt I 17 tL I— r h I ( F r•�� { `r-• r ' ir f • 1 I l.? I I I r,4 : , 1 ; , r1 j , , , tt; , 1 .I1 �1li .m.� � : r, r ._1 , .�, , _. . Ir� ,, , , 1' r. II ;I � IhI -•— '. ,. 4. ' . �w.; .L _',,..4 1 I ,.,—.--4---,T +,.{ ,.± r. -,-, ,H7-177-1-7- -1 I rt r I I 1 , �T $ 19 I 1 II � I ' . J. r 1 IF i -1- Ifr ;tll 1 I i 3 . I f . lr C I- �. 7 I �I _•,r1'ybvts ,, ' , I . I 1 r r -r i • i i JfH4J+ r t 1 1 F i {I 1 r �,I '.:'.1 ; tt. r ( 4 j.}. _ 1 1r , i4 ± r _ I I ,f, I { + I i , � 'll ;; I .. H 1 1n 1 'L I : . , it irk} f � � I 1 � 1 � . , �d :' Ir r I1 I E4 I ! 4 p{-3.1.- 111 r I- 1 . I I i- y3 allr9 Kcer6 • � ILI I tit. I ' � r� 1 f4 r Y7 . Y' Y w-- n _x`a •. y_k..'3.e.,_� --r '-1 ; I I •4b 1 - _.'_ �w�i -.ice{I > Y: ; ` `r •try ir_ III r ItFF �� �_. fi ti }.a x.+•rf II. I � I ' il._ 1 ;I �1 },y. l ( - Illh�\7 �leet�Q �� K' IsoO 1, ir rz •t • ,, _ `.?. I . ' ;.? `i' I _.F. I II I.�. I l . I i v ', j r. !,- - e R { 14-40-€1.----r-1 II .z r/ `t I � � y � t � 144?i II A� .0 ` � � t1 , 1 . 11 . 4 11 I r}}�I-�� r )) I ' I t I � ;tll r It F 1 I -1 LT i9 �� 411.1 �I 1-1i....6161�� L 'T . , , }� -: �fr � [ -1 . . II LI II 1 III -!- r , 1-:-, -1' If' I j 1 . I ` i,.. �L31(y I - , it.T rr t II _ I 7I cI II. l L.;rr I , i , 7t i BIG PIPESTONE CREEK - t EEK f I r � , t"I '7 I t , - I 1 y lyl - I - , ' ' f r + i C k I '' i CENTER LINE TYPICAL CROSS SECTIONS TY I I 1 I H • I I I I iIF ' I OF CHANNEL i ': • i `''a ` ' J r ''" -1 1 r i' r ' ` ` `:;.c: F BIG PIPESTONE CREEK ;I . j, { t (� .'ooYBBfr FLOOD PLAIN MANAGEMENT STUDY I k ri 4Gte c 'I 1 ���n oq teat I JEFFERSON COUNTY, MONTANA . 1 ' l _I`- VerO aicl 1 i inch= feel' , I' 1 ' 1..if — 10 year GROUND LINE •r:'3 I I � t ' - I 1—'. _ 'r•: ;i:• FLOOD ELEVATIONS• US OePARTMCNT O AORICIJLTUne SHEET 2 OF 3 k . I LEGEND O MT-N-85004-2 f ' I _ .- I I I. "•[ j ' : I I 4 I I Crass Section ` [ ICtoss Section `AD° ___ _ _. I 1-- ._T_ r•f — _r- 1 t y /h • d r r 1 I '-':•:•;:':'*.:.... ..., . e 3 t h r .•; ,.:..s-• , ,.L1,--._ i-r 7 - � .1.t !n' r v k t' r � .r•_..•s:_ F-{ .�' • S, �'. '' I '' ..: .. .. T tit I , } } . r �y { f t• _# 4Q00 �� gfrro Boo t F }y ' ijr' ± 8 ph, Q L + LLB} I , lir tl. 11: ',4—I i `' L_ h � 1 ' i , il+ Y ( r, 1 ' � r{- ' I , { 1 II ; o QO I r t FI t { j 4-1- ♦- 4.t t I I � t t r , ' + r r ' h I r Y I fiI,- 1 I_I r � {" ; Lfif I 4 r ' �- I- • j y-- � r I , -' I I { . . r . I , : I } .. , - H I I I i t > - , �} r II • I 1 , r .' •{ � _I •I . 1 r . 1 • I 71 r1' i_ I . . I , i ' � I 52 Y , L 1 1 b. rV 3 ` 1 II 1 I I LC -+{ - I ' r , 1 1 I-I •i 1"`�' [, I ` I I 1 I i' I I• L I : L '+•r -I-r- 1.1-} ,-}.FI I F +_+ F , I + IJ I I I f 1 I [�Y' 4' ' �' O r. . 1;r.,.e. 1 1 r l 1. r I �^ -1 r1 -4 f- .�I , I f YCi -r > F +} 7r Q It t $,. I [y , r1 '"� } . , : t:-it 1-1-1:11-1 : 111 L -I -i:L s u r I 'll ' I 1 ELI : I ".t.....;.:11 ; : t I 1 , 1i' ; .I , s I+ { L 1 i J I I t I h 1 I I 4 I rL: lint . ' r, r. lI � : I F t ' 4 • 1 rs .4 .i., .c.s r , r .f 1 440- r ..� - ' -. F I + t,� t ,t: w' • 3`•" 1 i +7.:>.{t:l F-'r i t L 1 I I 1 1 1 F 1 L 1 4! OP,-E I - I I ■ .3T I1 r} fah tit.-FM.S'� 1- I : 1 , ' I I f4 1 I ' j 1 11 ,:: . ,, i I, I (' t L }. �, t. I I 1 1 r - } 11 r; t r l 1 I III , I + f } F 14' OQ 1 Ihtl F :Ji : I ' "11" Tr 1 °- ++II ' III rI fr.' 11 11 1 1r I :: It! • L, I L4:4:014 1 11 ; �i { III ..1I - LI !. , I• -Yt I I �- y t r , . . �,adlas t ! ; rr I '_ 1 , , _ r , it I ' L t .., I 1 ..41 f f I vY I + � . I t1 ,1 - -Y 1 ++ , I 1 L F II I 1. . F I I S .1 1 1 f� _1_. fI 0-0ge -f.t` "4 pp I1_ i .amp' 1 ' t! r { 1 .:: :-.1' , I ' YI i L I I ', 1 r I1 1 } I ' 1 , 4a0 r + +r I F 1 r F F .a I , c t V sY--I-. r I 1 fi- 1 l r BIG i , r { I . 1,1.:.f j. � II F r . .J , - 1 , 1 yJ' _, If . I, , . - , r 1_ T {1 1 , I1 TYPICA �Ir II L [ I ` -- 74 r- I t .I , I ' I ' CENTER LINE I f I -_4 . 1 . - . 1 { ' I ' f - 1 1 rIf ' ' , i f -I 11 OF CHANNEL rrl` 1 t 4�so } f t f1 BIG I , -I L; , : 1 , . I I. FLOOD PLI 1 j1`` , $ I t ;.:•:. -- ... soo earn JEFFERS jr-. I 1 iocA Off fpe3 r ioo year F f f n I beijiba 1 ioph leer so year j I I I 1 i ' GROUND LINE'•' 10 Year _ _ I -ii"� i �,_ 1 • ...'..FLOOD ELEVATIONS f , f I 1 • I ' t ' It LEGEND I Oa NT I 4425 L o Cross Section "BC" 4450 z 4420 4445 et 4 4415 4440 w 0+00 4+00 5+00 "AS" ` +00 .4 zzo Cross Section AS 0+00 4+00 8+00 12 4435 Q } .): , SCALE Horizontal; 1 loch=200 feet. Cross Section "AW" Vertical: 1 inch=5 feet `" f BIG PIPESTONE CREEK CENTER LINE TYPICAL CROSS SECTIONS OF CHANNEL-..I .,! "" .'' BIG PIPESTONE CREEK FLOOD PLAIN MANAGEMENT STUDY " .••. •600 year JEFFERSON COUNTY, MONTANA �• 100 year I 4+00 8+00 12+00 16+ to 50 year GROUND LINE .-.. '• ::•• FLOOD ELEVATIONS LEGEND A a .cDnxiuwn eeTnDe NW"a DerywrueNT or .e ca1Vne SHEET 3 OF 3 MT-N-86004-3 4425 I . Cross Section "BC" 1 4420 •••:•••• :::::::::,...:::;;;;.:::::•.‘ o 4415 a0+00 4+00 8+00 Cross Section "AS" � `'` ° 0+00 a+00 a+0 if 0 8 aa 4435 3 SCALE • :• Horizonte 14 1 Inch-200 feet .: : Cross Section "AW" Vertical: 1 inch=6 feet 4430 i _ �� • CENTER LINE TY OF CHAN NEL 442s FLOO i -.. ..•• •....:600 year JEI 100 Year 0+00 4+00 3+00 12+00 16+ ,o year r• GROUND LIN •• . ..: FLOOD ELEVATIONS LEGEND O a"a. APPENDIX D TABLES1 - 4 1/° \ 411 "It TABLE 1 FLOOD DISCHARGES FOR SELECTED FREQUENCIES FOR STUDY REACH Study. Reach Drainage Area Peak Discharges Description (square miles) (cubic feet per second) 10-Yr. 50-Yr. 100-Yr. 500-Yr. Big Pipestone Creek Just above confluence with 114.4. 345 1,055 1,580 3,030 Little Pipestone Creek Just below confluence with 161.3 475 1,480 2,180 4,100 Little Pipestone Creek At confluence with 170.0 480 1,515 2,225 4,200 Jefferson Slough D-1 TABLE 2 FLOOD FREQUENCY-ELEVATION DATA (Elevations in Feet above National Geodetic Vertical Datum) Cross Channel Streambed 10-Year 50-Year 100-Year 500-Year Section Stationing Elevation Flood Flood Flood Flood Symbol Elevation Elevation Elevation Elevation BIG PIPESTONE CREEK A 00+00 4326.2 4329.7 4329.7 4329.8 4330.5 B 11+80 4327.5 4332.2 4332.4 4332.6 4333.5 C 19+10 4327.5 4333.4 4333.6 4334.1 4336.0 D 31+55 4335.0 4338.0 4338.1 4338.3 4339.5 E 43+30 4336.4 4341.2 4341.3 4341.4 4342.0 0 F 56+80 4339.9 4344,2 4344.4 4344.6 4345.6 N G 60+70 4341.2 4345.8 4345.9 4346.2 4346.8 H 60+95 4344.5 4346.8 4347.1 4347.3 4347.6 I 63+10 4344. 1 4347.9 4348.0 4348.1 4348.5 J 65+70 4343.4 4350.6 4351.0 4351. 1 4351.4 K 67+20 4344.9 4350.6 4351.0 4351.2 4351.5 L 68+50 4346.2 4350.6 4351.0 4351.2 4351.5 M 69+10 4345.9 4350.6 4352.0 4352.2 4352.4 N 69+95 4345.6 4350.6 4352.2 4352.2 4352.4 O 80+20. 4348.2 4352.0 4352.6 4352.9 4353.4 p 82+60 4348.4 4352.2 4353.0 4353.3 4353.9 Q 86+40 4349.8 4353.4 4354..0 4354.4 4354.9 R 93+20 4351.6 4355.9 4356.5 . 4356.6 4357. 1 S 98+50 4354.0 4358.0 4358.7 4358.9 4359.4 T • 103+50 4353.7 4359.1 4359.7 4359.9 4360.5 U 111+80 4354.1 4361.0 4361.8 4362.2 4362.9 ✓ 114+80 4356.6 4362.2 4363.3 4363.7 4364.5 W 116+90 4358.2 4364.0 4365.7 4366.9 4368.2 X 118+20 4357.9 4364.0 4365.7 4366.9 4368.2 Y 124+60 4359.9 4364.6 4365.9 4367.0 4368.3 Z 125+40 4360.3 4366.3 4367.4 4367.8 4368.6 TABLE 2--FLOOD FREQUENCY-ELEVATION DATA (Elevations in Feet above National Geodetic Vertical Datum) Cross 10-Year 50-Year 100-Year 500-Year Section Channel Streambed Flood Flood Flood Flood Symbol Stationing Elevation Elevation Elevation Elevation Elevation BIG PIPESTONE CREEK (continued) AA 125+80 4360.4 4366.3 4367.4 4367.8 4368.6 AB 128+30 . 4361.4 4366.7 4367.7 4368. 1 4369.0 AC 138+10 4363.6 4368.6 4370.0 4370.4 4371.6 AD . 148+90 4366.3 4371.6 4372.6 4372.9 4373.0 AE 162+90 4370.8 4376.2 4378.8 4379.8 4380.0 AF 177+20 4373.4 4378.6 4382.0 4383.4 4384.0 AG 191+40 4378.3 4384.4 4388.7 4390.7 4391.3 AN 204+50 4380.8 4387.6 4392.4 4394.7 4395.6 d AI 216+50 4383.8 4390.9 4396.5 4399.4 4400.7 w AJ 221+10 4385.9 4392.2 4397.6 4400.4 4402.1 AK 222+30 4391.3 4400..9 4402.4 4402.7 4403.5 AL 223+60 4391.8 4401.0 4402.7 4403.1 4404.5 AM 228+80 4393.0 4401.2 4403.3 4404.2 4405.8 AN 236+60 4394.8 4402.1 4405.3 4406.6 4407.1 AO 246+80 4399.0 4405.7 4410.0 4411.7 4412.6 AP 255+90 4402.9 4408.6 4412.5 4414.3 4415.7 AQ .272+40 4409.7 4416.6 4420.5 4421.4 4422.6 AR 273+30 4415.0 4419.1 4421.2 4421.8 4422.7 AS 274+9O 4416.2 4420.6 4422.2 4422.9 4424.5 AT 280+00 4416.9 4421.8 4423.2 4423.9 4425..2 AU 299+50 4422.4 4427.6 4429.3 4429.6 4429.8 AV 300+20 4424.1 4428.0 4429.7 4429.9 4430.9 AW 301+50 4423.7 4428.7 4430.8 4431.3 4432.3 AX 312+60 4426.4 4431.5 4433.8 4434.3 4435.4 AY 313+10 4425.6 4431.8 4435.7 4436.3 4437.2 AZ 314+35 4427.2 4432.4 4435.8 4436.4 4437.3 BA • 315+10 4430.6 4433.8 4436.0 • .4436.5 4437.4 BB 328+60 4434.6 4439.6 4441.0 4441.7 4442.7 BC 337+30 4437.4 4442.5 4444.1 4444.5 4445.1 BD 339+90 4439.0 4443.6 4445.5 4446.2 4447.2 BE 341+90 4439.5 4444.5 4447.0 4447.9 4448.7 TABLE 2--FLOOD FREQUENCY-ELEVATION DATA (continued) (Elevations in Feet above National Geodetic Vertical Datum) Cross 10-Year 50-Year 100-Year 500-Year Channel Streambed Section Stationing Elevation Flood Flood Flood Flood Symbol Elevation Elevation Elevation Elevation SOUTH OVERFLOW AREA - BIG PIPESTONE CREEK AO 0 4329.4 4331.5 4332.9 4333.2 4333.6 BO 8+00 4329.4 4332.3 4333.7 4334.0 4334.4 CO 17+00 4335.0 4336.1 4337.4 4337.7 4338. 1 DO 23+00 4336.6 4338.7 4339.6 4340.0 4340.3 EO 33+00 4340.1 4341.0 4342.0 4342.3 4342.7 FO 47+00 4343.6 4344.5 4345.6 4345.9 4346.6 GO 50+00 4345.1 4347.6 4348.4 4348.5 4349.0 HO 51+40 4344.9 4347.6 4348.4 4348.5 4349.0 iv IO 55+90 4346.0 4347.6 4348.4 4348.6 4349. 1 r JO 59+90 4347.2 4347.6 4348.8 4349.1 4349.7 TABLE 3 INCREASED DEPTH-REMAINING FLOODWAY WIDTH VALUES Cross Stream 100-Yr. Flood Plain 100-Yr. Floodway Total Width Section Channel Elevation Width For Increased Depths Symbol Width (ft.) (MSL) (ft.) 0.5 ft. 1.0 ft. BIG PIPESTONE CREEK A 18 4330.5 646 344 220 B 30 4332.6 573 30 30 C 42 4334.1 117 42 42 D 40 4338.3 240 40 40 E 19 4341.4 913 19 19 F 34 4344.6 34 34 34 G 28 4346.2 28 28 28 H 26 4347.3 553 138 101 I 31 4348. 1 481 229 149 J Road section 4351.1 County road/Culvert K 48 4351.2 637 637 557 L 24 4351.2 742 742 425 M Road section 4352.2 Old BN Railroad/Bridge N 24 4352.2 3889 1634 1253 O 42 4352.9 1831 741 554 P 28 4353.3 1050 513 371 Q 34 4354.4 1011 442 312 R 22 4356.6 1398 458 290 S 33 4358.9 1029 444 286 T 45 4359.9 822 474 324 U 28 4362.2 514 231 165 ✓ 33 4363.7 396 173 126 W Road section 4366.9 Montana Highway 55/Bridge X 18 4366.9 1304 679 574 Y 23 4367.0 1000 599 490 Z Road section 4367.8 County road/Bridge AA 30 4367.8 1113 488 387 AB 44 4368. 1 950 358 270 AC 46 4370.4 464 303 262 AD 32 4372.9 500 307 194 AE 42 4379.8 675 213 106 AF 56 4383.4 56 56 56 AG 33 4390.7 33 33 33 AH 44 4394.7 44 44 44 AI 40 4399.4 40 40 40 Al 80 4400.4 80 80 80 AK Road section 4402.7 Smith Road/Culvert AL 49 4403. 1 133 49 49 AM 80 4404.2 80 80 80 AN 51 4406.6 300 164 51 AO 51 4411.7 51 51 51 AP 58 4414.3 58 58 58 D-5 TABLE 3--INCREASED DEPTH-REMAINING FLOODWAY WIDTH VALUES (continued) Cross Stream 100-Yr. Flood Plain 100-Yr. Floodway Total Width Section Channel Elevation Width For Increased Depths Symbol Width (ft. ) (MSL) (ft. ) 0.5 ft. 1.0 ft. BIG PIPESTONE CREEK (continued) AQ 25 4421.4 333 222 136 AR 22 4421.8 395 68 48 AS 56 4422.9 566 428 317 AT 47 4423.9 540 371 283 AU 37 4429.6 1118 400 250 AV 38 4429.9 1139 425 250 AW 22 4431.3 1140 355 280 AX 14 4434.3 400 100 83 AY Road section County road/Bridge AZ 29 4436.4 599 309 213 BA 29 4436.5 612 335 233 BB 26 4441.7 297 105 83 BC 29 4444.5 663 313 168 BD Road section U.S. Highway 10/Bridge BE 55 4447.9 819 190 109 SOUTH OVERFLOW AREA - BIG PIPESTONE CREEK AO Undefined 4333.2 1774 566 438 BO Undefined 4334.0 1493 876 515 CO Undefined 4337. 7 940 470 470 DO Undefined 4340.0 850 306 201 EO Undefined 4342.3 626 265 240 FO Undefined 4345.9 917 389 335 GO Undefined 4348.5 County road HO Undefined 4348.5 2087 1004 805 IO Undefined 4348.6 1963 1120 936 JO Undefined 4349. 1 2100 931 790 D-6 TABLE 4 ACRES FLOODED 100-Year Flooded Area Data Stream Total Acres Channel Reach Flooded Acres Flooded Buildings Flooded 500-Yr. 100-Yr. Brush & Residences Farmsteads Businesses Farmland Riparian Urban Big Pipestone A - BE 953 580 298 271 11 45 6 2 Creek C APPENDIX E ELEVATION REFERENCE MARKS FLOOD PLAIN MANAGEMENT STUDY BIG PIPESTONE CREEK ELEVATION REFERENCE MARKS REFERENCE MARK ELEVATION IN FEET R.M. No. Survey No. (MSL) DESCRIPTION OF LOCATION 1 X 490 4474.48 C&GS bench mark stamped "X 490 1957." Present condition is good. Located 4.25 miles west along RN Railway from the station at Whitehall, .25 mile east of milepost 43, 74 rails west of the south rail, and 8 inches below the level of the track, in top of the south end of the west concrete abutment of a bridge. SE$ Sec 35 T2N R5W 2 R 3 4423.25 C&GS bench mark stamped "R 3 1907." Present condition is poor. Located 3.5 miles west along BN Railway from the station at Whitehall, NW of milepost 42, 79 feet north of the north rail, oy 591 feet north of the north right-of-way fence, 1 foot south of a white wooden witness post, 3 feet below level of the track, on the top of a 3-inch iron pipe that projects 2 feet, the pipe is bent to the west. SWk Sec 36 T2N R5W 3 Q 496 4405.66 C&GS bench mark stamped "Q 496 1957 ." Present condition is good. Located 2.5 miles west along the BN Railway from the station at Whitehall, 86k feet W-NW of milepost 41, 46 feet north of north rail, 72 feet northwest of center of private road crossing, 48 feet west of the centerline of field road, 1k feet south of fence 1k feet west of wooden witness post, 2 feet below level of track, on the top of a 3-inch iron pipe that projects 1 foot. SWk Sec 31 T2N R4W 4 W 490 4382.09 C&GS bench mark stamped "W 490 1957." Present condition is good. Located 1.5 miles west along EN Railway from the station at Whitehall, 734 feet NE of milepost 40, 434 feet north of the north rail, 3 feet south of fence, 2 feet west of white witness post, 21 feet below the level of the track, and in the top of a concrete post projecting 5 inches. NE' Sec 5 TIN R4W ELEVATION REFERENCE MARKS BIG PIPESTONE CREEK (continued) REFERENCE MARK ELEVATION IN FEET DESCRIPTION OF LOCATION R.M. No. Survey No. (MSL) 5 B 495 4365.42 C&GS bench mark stamped "B 495 1957." Present conditon is good. Located .5 mile west along the BN Railway from the station at Whitehall, 56 feet NE of milepost 39, 46k feet north of the north rail, 164 feet NE of the center of the crossing of an asphalt road, 61 feet SE of the centerline of the asphalt road, 13k feet east of apower pole, 2 feet north of a. white wooden witness post, level with the rails, and in the top of a concrete post projecting 6 inches. NW' Sec 4 T1N R4W 6 P90A 4348.3 SCS temporary bench mark. Top of spike in railroad tie, located .4 mile south on BN Railway from station at Whitehall, 7.5 feet north of north bridge abutment over Big Pipestone Creek, in 1 centerline of tracks. SE' Sec 4 TIN R4W N 7 P-50 4345.0 SCS temporary bench mark. Top of 5/8" REBAR located about .3 mile south of U.S. Highway 10, 20 feet west of entrance road to Whitehall sewage lagoons, 50 feet north of gate in E-W fenceline, top of REBAR 4 inches above ground level. SW' Sec 3 T1N R4W 8 S 490 4352.52 C&GS bench mark stamped "S 490 1957." Present condition is good. Located .7 mile east along BN Railway from station at Whitehall, about .2 mile east of milepost 38, 79 feet north of rail of the main track, 17 feet south of centerline of the highway, 4 feet above the level of highway, 6 feet above level of the track, in the top of a large square concrete pillar at the southwest corner of U.S. Highway 10 bridge over Whitetail Creek. NEk Sec 3 TIN R4W 9 P-20 4337.4 SCS temporary bench mark. Top of 5/8" REBAR located at the SE corner of east sewage lagoon SE of Whitehall, top of bank, 50 feet north of E-W fenceline, top of REBAR 4 inches above ground level. 5E1 Sec 3 TIN R4W APPENDIX F INVESTIGATION AND ANALYSES INVESTIGATION AND ANALYSES Standard hydrologic and hydraulic study methods were used to determine data for channel capacities , flow velocities, and flood elevations. Detailed methods were used on the entire study reach. The 10-, 50-, 100-, and 500-year flood events were selected for listing in this report because of their significance for flood insurance and flood plain management. Hydrologic Analyses Hydrologic analyses were carried out to establish the peak discharge-frequency relationships for floods on the Big Pipestone Creek study reach. The final peak discharge-frequency curve was developed using the SCS TR20 Project Formulation-Hydrology computer model (Reference 8) . This method was selected because of insufficient gage data in the study area and the need to model the effect of the Delmoe Lake irrigation reservoir in the upper watershed. The watershed area contributing runoff to the study reach was broken into five subwatersheds and data were developed for each as input into the TR20 model. Data required for the model include drainage area, time of concentration, runoff curve number, channel reach length, channel routing parameters, and precipitation amounts, duration, and distribution. Drainage areas and topographic information needed for times of concentration estimates were developed from 71-minute and 15-minute USGS quadrangle maps (Reference 16) . Soils information needed to develop runoff curve numbers was obtained from a statewide general soils map (Reference 9), from SCS soil scientists, and from Forest Service personnel. Landuse types and conditions also needed for runoff curve number development were made from onsite observation and aerial photographs. Channel reach and routing data were F-1 developed from USGS quadrangle maps of the upper watershed and from cross-section surveys in the study reach. Precipitation values and distributions were derived from National Oceanic and Atmospheric Administration Atlas 2 for Montana (Reference 10) for the 24-hour duration storm used in the TR20 model. One of the subwatersheds was the drainage area into Delmoe Lake reservoir. Storage data for the reservoir were taken from miscellaneous information in SCS files. Discharge curve for the emergency spillway was developed using the weir equation. The reservoir was assumed to be at the crest of the spillway at the beginning of the various storms analyzed. Results from the TR20 model were checked by comparing peak discharges with stream gage analyses and with flood elevations of past floods. The only gage data in the Big Pipestone Creek watershed area were 1 year of record collected in 1911 on Big Pipestone Creek above the Little Pipestone Creek confluence and 6 years of record collection from 1935 through 1940 on Little Pipestone Creek. Because these data were not adequate to develop positive conclusions, data from surrounding gage stations had to be investigated. Data from 35 stream gage stations in southwestern Montana were initially reviewed. The data were retrieved and analyzed using the USGS Peak Flow Retrieval and Flood Frequency Analysis computer programs on the USGS National Water Data Storage and Retrieval System in Reston, Virginia (Reference 11). Water Resource Council Bulletin 17B procedures were used (Reference 12) . Of these 35 stations, 15 were selected for use in developing simple regression equations using drainage area as the independent variable F-2 against discharges for various frequencies. These equations checked well with the TR20 model at the 100-year frequency, but indicated that the TR20 model may be low at the 10-year frequency. .USGS regression equations in Open File Report 81-917 were also used for another check (Reference 13). These equations indicated slightly smaller peaks than the equations developed from the 15 gages in this study, but they were similar. Flooding history indicates that the lower 10-year peak from the TR20 model is a better estimate from the area flooded-frequency standpoint. Also, the TR20 model produced peaks which gave flood elevations and flood areas matching the 1981 flood observed values when using rainfall amounts estimated to have occurred during that storm. The 1981 flood was estimated to be a 10- to 20-year event. Flood elevations and areas for the 100-year peak flow from the TR20 model also appear reasonable. Therefore, the peak discharge-frequency curve from the TR20 model is considered valid for this study. Hydraulic Analyses Analyses of the hydraulic characteristics of the Big Pipestone Creek study reach were carried out to provide estimates of the flood elevations and flow velocities for selected frequencies. F-3 Water surface elevations were determined using the SCS WSP2 computer program to perform subcritical flow backwater computations. The program computes head losses at roadways using the U.S. Bureau of Public Roads methods (References 14 and 15). Water surface computations were initiated using a conservative slope of 0.001 ft/foot. A separate WSP2 run was made for the out-of-bank flow area south of the main creek channel in the lower reach southeast of Whitehall. Channel roughness factors (Mannings "n") used for the study area varied from 0.035 for clean channel sections to 0.08 for brushy channel areas. On the flood plain segments, values from 0.04 for smooth, open areas to 0.11 for brush-covered areas were used. Cross-section data used in the WSP2 program were taken directly from field survey data. The surveys, were conducted by SCS personnel between fall of 1983 and spring of 1984. USGS 7I-minute quadrangle maps were used to establish horizontal orientation and to check horizontal control (Reference 16). Vertical control was established using closed level circuits tied into U.S. Coast and Geodetic Survey bench marks located along the Burlington Northern railroad in the study area. (See appendix E.) Elevations for these bench marks are referenced to the National Geodetic Vertical Datum (NGVD) of 1929. Stereo photo coverage was used to draw flood boundaries between surveyed cross sections shown on the flood hazard maps. Photo background for flood maps is taken from ASCS 1981 photography enlarged to a scale of 1 inch equals 500 feet (Reference 17). F-4 Flood profiles were drawn for the main Big Pipestone Creek channel only. Profiles show the location of cross sections and road crossings corresponding with the flood hazard maps. 1-5 GLOSSARY O F TERMS cfs Cubic feet per second (a unit of measure of liquids flowing past a given point) cross section Shape and dimensions of a channel and valley perpendicular to the line of flow. drainage area (Also drainage, watershed, catchment basin) The total surface area above a given point that would contribute to flow at that point in the event of runoff. event A storm which produces runoff, also a flood. flood A runoff event which causes flooding. floodini{ The temporary inundation of lands not normally subject to flowing or standing water which causes or threatens to cause damages. flood frequency (See recurrence interval) flood hazard area (Also flood plain or flood-prone area) Land adjacent to a channel or in a low area which is subject to flooding. flood plain (See flood hazard area) flood profile (Also profile) A plotted line showing the highest water surface elevation along a stream for a particular flood. frequency (See recurrence interval) hydraulics . (hydraulic analysis) General--the science that treats water in motion. For this report--the determination of the depth and velocity of various discharges at given cross sections. hydrology (hydrologic analysis) General--the science that deals with the occurrence and behavior of water in the atmosphere, on the ground, and underground. For this report--the determination of peak rate of discharge from a given drainage area for various frequencies using various procedures including gage data analyses, regional regression analyses, and application of watershed modeling techniques. G-1 GLOSSARY OF TERMS (continued) overland flow Runoff which flows over the ground surface in a shallow layer as opposed to channelized runoff. peak discharge The highest discharge or rate of flow during a flood at a given point. peak flood elevation The highest stage or elevation reached by a flood at a given point. recurrence interval (Also return period, frequency) The average interval of time within which the magnitude of a flood will be equaled or exceeded. It can be expressed in years or percent chance. Examples: A 10-year flood or 10-year frequency flood is one which can be expected to be equaled or exceeded once every 10 years on the average. (It has a recurrence interval or return period of 10 years.) Also, a 10-year flood has a 10-percent-chance of being equaled or exceeded in any given year. 2-yr. flood--every 2 yrs.--50 percent chance 5-yr. flood--every 5 yrs.--20 percent chance 25-yr. flood--every 25 yrs.--4 percent chance 50-yr. flood--every 50 yrs.--2 percent chance 100-yr. flood--every 100 yrs.--1 percent chance 500-yr. flood--every 500 yrs.--0.2 percent chance return period (See recurrence interval) riparian area The vegetated area and biotic community influenced by high water tables adjacent to rivers, streams, and other surface waters. routing (Also flood routing) The computation of the changes in the rise, peak, and fall of streamflow as a flood moves through a channel or reservoir. runoff (Also excess rainfall) That portion of rainfall which contributes to flow in a channel or across the land surface. watershed (See drainage area) G-2 B I B L I O G R A P H Y 1. U.S. Bureau of Commerce, Bureau of the Census. Local Population Estimates, Series P-26. February 1984. 2. U.S. Bureau of Commerce, Bureau of the Census. 1980 Census of Population, Volume I, Characteristics of the Population, Montana. October 1981. 3. U.S. Army Corps of Engineers. Phase I Inspection Report, National Dam Safety Program, Delmoe Lake Dam Butte, Montana Jefferson County MT-1117. Prepared by CH2M HILL. April 1980 4. U.S. Department of Commerce, Weather Bureau. Climatic Summary of the United States, Supplement for 1951 through 1960. 1965 5. U.S. Department of Agriculture, Soil Conservation Service. Average Annual Precipitation, Montana. 1977 6. L. C. Hanson Co. , Helena, MT. gig Pipestone Creek, Preliminary Study and Reclamation Plan. July 1982. 7. U.S. Department of the Interior, Geological Survey. Floods of May 1981 in West-Central Montana. June 1982. 8. U.S. Department of Agriculture, Soil Conservation Service. Computer Program for Project Formualtion-Hydrology. Technical Release 20, Draft. May 1982. 9. Montana Agricultural Experiment Station, Montana State University and USDA, SCS. Soil of Montana. Bulletin 744. November 1982. 10. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service. NOAA Atlas 2, Precipitation-Frequency, Atlas of the Western United States, Volume I, Montana. 1973. 11. U.S. Department of the Interior, Geological Survey. WATSTORE Peak Flow File. Reston Computer Center. January 1984. 12. U.S. Water Resources Council. Guidelines for Determining Flood Flow Frequency. Bulletin 17B. September 1981. 13. U.S. Department of the Interior, Geological Survey. Revised Techniques for Estimating Magnitude and Frequency of Floods in Montana. Open File Report 81-917 . September 1981 . 14. U.S. Department of Agriculture, Soil Conservation Service, Engineering Division. WSP-2 Computer Program. Technical Release No. 61. May 1976. 15. U.S. Department of Transportation, Bureau of Public Roads. Hydraulic Design Series No. 1 , Hydraulics of Bridge Waterways. Second Edition. 1970. H-1 16. U.S. Department of the Interior, Geological Survey. 71/4-minute series quadrangles: Whitehall, Black Butte, Vendome, Dry Mountain, Grace, and Homestake, 1963, photo revised 1978; Delmoe Lake and Pipestone Pass, 1963; 15-minute series quadrangle: Elk Park, 1954. 17. U.S. Department of Agriculture, Agricultural Stabilization and Conservation Service. Aerial Photography of Jefferson County. Scale 1:40000. August 1979. H-2 APPENDIX I LEGAL REFERENCE 1 Montana Code Annotated Montana Floodplain and Floodway Management Act Part I General Provisions ' 76-5-101 . Findings. The people of the state of Montana find that: (1) recurrent flooding of a portion of the state' s land resources causes loss of life, damage to property, disruption of commerce and governmental services, and unsanitary conditions; ' all of which are detrimental to health, safety, welfare, and property of the occupants of flooded lands and the people of this state; and ' (2) the public interest necessitates management and regulation of floodprone lands and waters in a manner consistent with sound land and water use management practices which will prevent and alleviate flooding threats to life and health and reduce private and public economic losses. 76-5-102. Policy and purposes. (1) The policy and purposes of parts 1 through 4 of this chapter are to: (a) guide development of the floodway areas of this state consistent with the enumerated findings; (b) recognize the right and need of watercourses to periodically carry more than the normal flow of water; (c) provide state coordination and technical assistance to local units in management of floodway areas; (d) coordinate federal , state, and local management activities for floodway areas; (e) encourage local governmental units to manage floodprone ' lands, including the adoption, enforcement, and administration of land use regulations; and ( f) provide the department of natural resources and conservation with authority necessary to, carry out a comprehensive floodway management program for the state. ( 2) Specifically, it is the purpose of parts 1 through 4 to: (a) restrict or prohibit uses which are dangerous to health or safety or property in times of flood or cause increased flood heights or velocities; (b) require that uses vulnerable to floods, including public facilities which serve such uses, be provided with flood protection at the time of initial construction; ' (c) develop and provide information to identify lands which are unsuited for certain development purposes because of flood hazard; ' (d) distinguish between the land use regulations applied to the designated floodway and those applied to that portion of the designated floodplain not contained within the designated floodway; ' (e) apply more restrictive land use regulations within the designated floodway; 1 1 (f) ensure that regulations and minimum standards adopted , under parts 1 through 4 , insofar as possible, balance the greatest public good with the least private injury. 76-5-103 . Definitions. As used in part:. 1 through 4 of this chapter , unless the context otherwise requires , the following definitions apply: ' ( 1) "Artificial obstruction" means any obstruction which is not a natural obstruction and includes any dam, wall, ripran, embankment, levee, dike , pile , abutment, projection, revetment, excavation, channel rectification, bridge, conduit, culvert, building, refuse, automobile body, fill, or other analogous structure or matter in, along , across, or projecting into any floodplain or floodway which may impede, retard , or change the direction of the flow of water , either in itself or by catching or collecting debris carried by the water, or that is placed. where the natural flow of the water would carry the same downstream to the damage or detriment of either life or property. (2) "Poard" means the board of natural resources and conservation provided for in 2-15-3302 . ( 3) "Channel" means the geographical area within either the natural or artificial banks of a watercourse or drainway . (4) "Department" means the department of natural resources and conservation provided for in Title 2 , chapter 15, part 33. ( 5) "Designated floodplain" means a floodplain whose limits have been designated and established by order of the board . (6) "Designated' floodway" means a floodway whose limits have ' been designated and established by order of the board. (7) "Erainway" means any depression 2 feet or more below the surrounding land serving to give direction to a current of water less than 9 months of the year and having a bed and well-defined. banks . ( E) "Establish" peens construct , place , insert, or excavate. ( 9) "Flood" means the water of any watercourse or drainway which is above the hank or outside the channel and banks of such watercourse or drainway. (10) "Flood of 100-year frequency" means a flood magnitude expected to recur on the average of once every 100 years or a flood macnitude which has a 1% chance of occurring in any giver year . 111(11) "Eloodpiain" means the area adjoining the watercourse or drainway which would be covered by the floodwater of a flood of 100-year frequency , except for sheetflood areas that receive less than 1 foot of water per occurrence and are considered "zone F" by the federal emergency management agency. (12) "Floodway" means the channel of a watercourse or drainway '. and those portions of the floodplain adjoining the channel which are reasonably required to carry and discharge the floodwater of any watercourse or drainway. (13) "natural obstruction" means any rock, tree, gravel , or analogous natural natter that it an obstruction and has been located within the flcodplain or floodway by a nonhuman cause. (14) "Owner " means any person who has dominion over, control , of, or title to an obstruction. • 1 I . (15) "Political subdivision" means any incorporated city or town or any county organized and having authority to adopt and ' enforce land use regulations. (16) "Eesponrible political subdivision" means a political subdivision that has enacted land use regulations in accordance ' with parts 1 through 4 . ( 17) "Uatercourse" means any cepre::s1on 2 feet or more below the surrounding lane serving to give direction to a current of III water at least 9 months of the year and having a bed and well—defined banks; provided that it shall, upon order of the • board , also include any particular depression which would not otherwise be within the definition of watercourse. ' 76-5-104. Presumption that depression is watercourse. In the event of doubt as to whether a depression is a watercourse or ' drainway, it shall be presumed to be a watercourse. • 76-5-105 . Authority to enter and - investigate lands or waters. The department or the responsible political subdivision may make reasonable entry upon any lands and waters in the state for the purpose of raking an investigation, survey, removal, or repair contemplated by parts 1 through 4 of this chapter. IT ' investigation of a natural or artificial obstruction or nonconforming use shall he made by the department either on its own initiative, on the written request of three titleholders of lane abuttino the watercourse or drainway involved , or on the written request of a political subdivision. ' 76-5-106 . Exemption for small drainage area. Parts 1 through 4 of this chapter shall not extend to any obstruction in the floodplain or floodway of a watercourse or drainway where the drainage area above the same , either within or without the state, ' is less than 25 square miles in extent unions a particular watercourse or drainway is expressly declared to be within the coverage of. parts 1 through 4 by order of the board. 1 76-5-107 . Federal supremacy. Parts 1 through G do not interfere with the right of the United States to regulate interstate ' commerce or the navigable waters of the United States. 76-5-108. Permit construed as added requirement. The eranti. g of a permit under parts 1. through 4 of this chapter Coes not affect any other type of approval reeuiree by any other statute or ordinance of the state, of any •i•'o1itical subdivision , or of the United States hut is an added requirement. 76-5-109. Other legal remedies preserved—immunity. (1) The grant or denial of c permit does not have an effect on a remedy of a person at law or in equity. (2) Fhere it ir shown that there is a wrongful failure to comply with fart : 1 through 4 of this chapter , there is a rebuttable presumption that the obstruction was the proximate cause of the flooding of the land of a Berson bringing suit. 1 • (3) . The use of any one of the remedies or powers given to the board or the department in parts 1 through 4 is net a tar to the exercise of any other remedy or power given by parts 1 through 4 . (4) An action for damages sustained because of injury caused by an obstruction for which a permit has been granted under part ] through 4 may not be brought aoainst the state, the board, a member of the board , or the department . 76-5-110 . Penalties for violation. Any person who violates 76-5-401 through 76-5-404 shall be guilty of a misdemeanor and shall upon conviction thereof be fined not more than $100 or be imprisoned in the county jail for not nore than 10 days or be both so fined and imprisoned. Each day' s continuance of a violation shall be deemed a separate and distinct offense. Part 2 Role of State Agencies 76-5-201 . Program for delineation of floodplains and floodways. (1) The department shall initiate a comprehensive precrara for the delineation of designated floodplains and designated floodways for every watercourse and 'drainway in the state. It shall make a study relating to the acquiring of flood data and may enter into arrangements with the United States geological survey, the United Ftates army corps of engineers, or any other state or federal agency for such acquisition. (2) Pefore the hoard establishes by order a designated floodplain or a designated floodway, the department shall consult with the affected political subdivisions. Consultation shall include but not be limited to the following: (a) specifically requesting that the political subdivisions submit pertinent data concerning flood- hazards , including flooding experiences, plans to avoid potential hazards , estimates of economic impacts of flooding on the community, both historical and prospective, and such other data as considered aippropriate; (b) notifying local officials, including members of the county commission, city council, and planning board, of the progress of surveys , studies , and investigations and of proposed findings , along with information concerning data and methods employed in reaching such conclusions; and (c) encouraging local dissemination of information concerning surveys, studies , and investigations so that interested persons will have an opportunity to bring relevant data to the attention of the department. 76-5-202 . Designation of floodplains and floodways. (] ' t'hen ' sufficient data have been acquired', by the department, the heard shall establish , by order after a public hearing , the designated floodplain within which a political subdivision may establish lane use regulation. ( 2) [?hen sufficient data have been acquired, the board shall establish, by order after a public hearing , the designated floodway within which a political subdivision may establish land use regulation. 1 (3) These designations shall he based upon reasonable hydrological certainty. ' (4) The department shall record all designated floodplains or designated floodways established by the board in the office of the county clerk and recorder of each county in which those ' floodplains or floodways are found . 76-5-203 . Alteration of floodplains or floodways. The board may alter the floodplains or floodways at any later time, by order ' after a public hearing , if a reevaluation of the then available flood data warrants it. 76-5-204 . What constitutes notice. Notice of a hearing or order of the board establishing or altering the floodplains or floodways shall be given by publishing the notice once each week for 3 consecutive weeks in a legal newspaper published or of general circulation in the area involved, the last publication of which shall be not less than 10 days prior to the crate set for the hearing or the effective date of the order. 76-5-205. Furnishing of material to local governments. ( 1 ) ! tree the designated floodplain or the designated floodway has been established , the department shall furnish these data to officials cf the political subdivision having jurisdiction over those areas., together with a map outlining the areas involved, a copy ' of parts 1 through 4 of this chapter , adopted rules of the hoard , and suggested minimum standards adopted by the board. (2) These standards and rules shall reflect graduations in flood hazard based on criteria as outlined in 76-5-406. In adopting these standards and rules , the hoard shall consider local input from the affected political subdivisions. 76-5-206 . Powers and duties of department relative to obstructions. (1) ?'here an obstruction to a designated floodway established under 76-5-202 through 76-5-205 has been created by fallen trees, silt , debris , wreckage , unanchored automobile bodies, and like matter , the department may, in its discretion, remove the obstruction, in which case the cost of removal shall be borne by the department. I (2) ?;here, after investigation, notice, and hearing , an order. has been issued by the board to the owner of an obstruction net exempt under 76-5-407 through 76-5-404 for its removal or repair and the order is not complied with within such reasonable time as nay be prescribed or if the owner cannot be found or deteriincd, the department may make or cause the removal or repairs tc be made, the cost of which shall he borne by the owner and shall be recoverable in the sane manner as debts are now recoverable by law. ' 76-5-207 . Floodway obstruction removal fund. The state treasurer shall establish the flondway obstruction removal fund and credit to the fund for the removal of obstructions as provided in 76-5-:06 (1 ) such money specifically appropriated by 1 1 the legislature. The department may allocate money from the floodway obstruction removal fund for purposes provided in 76-5-206 (1) . ' 76-5-208. Orders and rules. (1) The board may adopt such orders and rules as are necessary to implement parts 1 through c of this chapter. 111 orders and rules adopted by the board shall be on file at the offices of the department and in the office of the county clerk and recorder of each county affected by the order or rule. (2) If an order is issued to the owner of an artificial obstruction or nonconforming use not exempt under 76-5-401 through 76-5-404 for its removal or repair, the order shall not become effective less than 10 days after a hearing is held relating to the order . (3) In addition to any requirement imposed by 76-5-202 through 76-5-205 , where an order is issued which affects with particularity the land adjacent to a watercourse or drainway, notice of the contents of the order and of any required hearing shall be mailed by the department to the titleholder of the land not less than 10 clays before the effective date of the order or, if there is a required hearing , to the titleholder of the land and to the owner of the artificial obstruction or nonconforming_ use not less than 10 days before the date of the hearing . Powever , the notice need not be given to the owner of the artificial obstruction or nonconforming use for an order i:.sued pursuant to 76-5-206 (2) if the owner cannot be found or determined . 76-5-209. Appeal from board order. (1) A. person aggrieved by any order of the hoard issued under parts 1 through 4 of this chapter may appeal from the order to a court of competent jurisdiction within 30 days after its effective date. Service of notice of the appeal shall be mode upon the department. (2) If an appeal is taken, enforcement of the order shall be stayed pending the outcome of the appeal. Part 3 Role of Local Government ' 76-5-301 . Land use regulations. (1) Upon transmittal of the floodplain information to officials of a political subdivision, the political subdivision has C months from the date of transmittal to adopt land use reGul.ations which meet or exceed the minimum standards of the board . (2) If within the 6-month period the political subdivision has failed to adopt the land use regulations, the department shall enforce the minimum standards within the designated floodplain or the designated floodway as established by the hoard under 76-5-202 through 76-5-205 , and no artificial obstruction or nonconforming use may be established by any person within the designated floodplain or the designated floodway unless specifically authorised: by the board . 1 ' (3) A political subdivision which has failed to adopt land use regulations which meet or c :coed the minimum standards of the board within the 6-month period may subsequently adopt such I regulations , and if approved by the hoard , they shall be effective within the designated floodplain or floodway and administered and enforced by the political subdivision. ' (4) When necessary for compliance with federal flood innur=nee requirements , the board may shorten the 6-month period upon notification to the political subdivision and publication of a I notice thereof in a newspaper of general circulation in the affected area once a week for 3 consecutive weeks. 76-5-302. Substitution of local control for state permit system. ' (1) If a political subdivision enacts, in harmony with the purposes of parts 1 through 4 of this chapter, permit issuance ordinances, regulations , or resolutions and land use ordinances , ' regulations, or resolutions which meet or eiceed the minimum standards of the board and if the administrative and enforcement procedures established for those ordinances, regulations, or I resolutions are found acceptable by the board, no permit fro the department is required: . (2) However, if the board determines that there is a failure by a political subdivision to comply with the intent, purposes , and I provisions of parts 1 through r. and the minimum standards auortee, thereunder , the powers of the political subdivision may be suspended after hearing and the minimum standards adopted by the I board shall be enforced by the department until such time as the board determines that the political subdivision will campy . ' Part 4 Use of Floodplains and Floodways ' 76-5-401 . Permissible open-space uses. The following open-space uses shall be permitter within the designated floodway to the extent that they are not prohibited by any other ordinance or I statute and provided they de not require structures other than portable structures, fill, or permanent storage of materials or equipment : ' (1) agricultural use,; (2) industrial-commercial uses such as loading areas, parking areas , or emergency landing strips; (3) private and public recreational uses such as golf courses, ' tennis courts, driving rLnnc. - , archery ranges, picnic grounds, boat in les nching ramps, swimming areas, parks , wildlife managdement and natural areas , cane farms , fish hatcheries, shooting I preserves, target ranges , tram and skeet ranges, hunting an: fishing areas , or hiking and horseback riding trails; (4) forestry , including processing of forest products with ' portable equipment ; (5) residential uses such as lawns , gardens, parking areas, and play areas; J (6) e:.cavations subject to the issuance of a permit under I76-5-405 and 76-5-406 . I • 76-5-402. Permissible uses within floodplain but outside of ' floodway. Permits shall be granted for the following uses within that portion of the floodplain not contained within the designated floodway to the extent that they arc not prohibited by any other ordinance, regulation, or statute: . (1) any use permitted in the designated floodway; ( 2) structures, including but not limited to residential, commercial, and industrial structures , provided that: (a) such structures meet the minimum standards adopted by the board; (b) residential structures are constructed on fill such that the lowest floor elevation ( including basements) is 2 feet above the 100-year flood elevation; (c) commercial and industrial structures are either constructed on fill as specified in subsection (b) or are adequately floodprocfed up to an elevation no lower than 2 feet above the 100-year flood elevation. Such floodproofing shell be in accordance with the minimum standards adopted by the board. 76-5-403 . Prohibited uses within floodway. The following nonconforming uses shall be prohibited within the designated floodway: (1) a building for living purposes or place of assembly or permanent use by human beings; (2) a structure or excavation that will cause water to be diverted from the established floodway, cause erosion, obstruct the natural flow of water , or reduce the carrying capacity of the floodway; ( 3) the construction or permanent storage of an object subject to flotation or movement during flood level periods . 76-5-404. Artificial obstructions and nonconforming uses. (1) An artificial obstruction or nonconforming use in a designated floodplain or designated floodway enforced under 76-5-201 (1) and (2) and not exempt under subsections ( 2) or (3) of this section or 76-5-401 through 76-5-403 is a public nuisance unless a permit has been obtained for such artificial obstruction or nonconforming use from the department or the responsible political subdivision. (2.) It is unlawful for a person to establish an artificial obstruction or nonconforming use within a designated floodplain or a designated floodway without a permit from the department or the responsible political subdivision. (3) (a) Parts 1 through 4 of this 'chapter Co not affect any existing artificial obstruction or nonconforming use established in the designated floodplain or designated floodway before the land use regulations adopted by the political subdivision are effective or before the hoard has enforced a designated floodplain or a designated floodway under 76-5-301 ( 1) and (2) . (b) Powever, a person nay not make nor may an owner allow alterations of an artificial obstruction or nonconforming use within a designated floodplain or a designated floodway whether the obstruction proposed for alteration was located in the floodplain or floodway before or after July 1 , 1071 , ereelt upon 1 I Iexpress written approval of the department or the responsible political subdivision. raintenance of an obstruction is not an I alteration. 76-5-405. Variance for obstruction or nonconforming use. (1) The department or the responsible political subdivision I may issue permits for the establishment or alteration of artificial obstructions and nonconforming uses which would; otherwise violate 76-5-401 through 76-5-404 . The application for the permit shall be submitted to the department or the responsible political subdivision and contain such information as the department requires, including complete maps, plans, I profiles , and specifications of the obstruction or use and watercourse or drainway. (2) Permits for obstructions or uses to he established in the designated floodplain or designated floodway of watercourses must I be specifically approved or denied within a reasonable tire by the department or the responsible political subdivision. Permits for obstructions or uses in the designated floodplains or I designated floodways shall be conclusively deemed to have been granted 60 days after the receipt of the application by the department or the responsible political subdivision or after such ' time as the board or the responsible political subdivision shall specify, unless the department or the responsible political subdivision notifies the applicant that the permit is denied. The responsible political subdivision shall send to the I department a copy of each permit granted pursuant to this section and 76-5-406. (3) /\.n application for a permit shall be accompanied by a I nonrefundable application fee of. $10 which the state treasurer shall credit to the floodway obstruction removal fund. (4) The department or the responsible political subdivision I may make a part of the permit any reasonable conditions it may consider advisable. - In order for the permit to continue to remain in force, the obstruction or use must be maintained so as to comply with the conditions and specifications of the permit. I76-5-406 . Criteria to be considered in connection with variance request. In passing upon the application, the department or the responsible political subdivision shall consider in accordance with the minimum standards established by the board: ( 1) the danger to life and property by water which nay be I backed up or diverted by the obstruction or use; (2) the danger that the obstruction or use will be swept downstream to the injury of others; I - (3) the availability of alternate locations; - • ( 4) the construction or alteration of the obstruction or use in such a manner as tc lessen the danger ; (5) the permanence of the obstruction . or use; I ( 6) the anticipated development in the foreseeable future of the area which may be affected by the obstruction or use; and (7) such other factors as are in harmony with the purpose of parts 1. through 4 of this chapter . I I . . . . Icypress written approval of the department or the responsible political subdivision. Faintenence of an obstruction is not an I alteration. 76-5-405 . Variance for obstruction or nonconforming use. (1) The department or the responsible political subdivision • I may issue permits for the establishment or alteration of artificial obstructions and nonconforming uses which would otherwise violate 76-5-401 through 76-5-404. The application for I the permit shall be submitted to the department or the responsible political subdivision and contain such information as the department requires, including complete maps, plans, I profiles , and specifications of the obstruction or use and watercourse or cirainway. (2) Permits for obstructions or uses to be established in the designated floodplain or designated floodway of watercourses must ' be specifically approved or denied within a reasonable tire by the department or the responsible political subdivision. -Permits for obstructions or uses in the designated floodplains or I designated floodways shall be conclusively deemed to have been granted 60 days after the receipt of the application by the department or the responsible political subdivision or after such I time as the board or the responsible political subdivision shall specify, unless the department or the responsible political subdivision notifies the applicant that the permit is denied. The responsible political subdivision shall send to the I department a copy of each permit granted pursuant to this section and 76-5-406 . (3) Tn application for a permit shall be accompanied by a I nonrefundable application fee of ;10 which the state treasurer shall credit to the floodway obstruction removal fund. (4) The department or the responsible political subdivision may make a part of the permit any reasonable conditions it may I consider advisable. In order for the permit to continue to remain in force , the obstruction or use must be maintained so as I to comply with the conditions and specifications of the permit. • 76-5-406 . Criteria to be considered in connection with variance request. In passinc upon the application, the department or the ' responsible political subdivision shell consider in accordance with the minimum standards established by the board; (1) the dancer to life and property by water which may be I backed up or diverted by the obstruction or use; (2) the danger that the obstruction or use will be swept downstream to the injury of others ; (3) the availability of alternate locations; I ( 4) the construction or alteration of the obstruction or use in - such a manner as tc lessen the danger ; (5) the permanence of the obstruction - or use; I (6) the anticipated development in the .foreseeable future of the area which may be affected by the obstruction or use ; and (7) such other factors as are in harmony with the purpose of ' parts 1 through 4 of this chapter . I • DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION CHAPTER 15 FIAODPLAIN MANAGEMENT ENGINEERING BUREAU Sub-Chapter 1 Definitions Rule 36.15.101 Definitions 1 Sub-Chapter 2 Regulation and Enforcement ' Rule 36.15.201 Local Regulation and Enforcement 36.15.202 Board Approval of Local Regulations and Enforcement 36.15.203 Time Limit for Adoption of Local Regulations ' 36.15.204 Local Regulations - Requirements Rules 36.15.205 through 36.15.208 Reserved 36.15.209 Department Regulation and Enforcement 36.15.210 Environmental Impact Statements Rules 36.15.211 through 36.15.215 Reserved 1 36.15.216 Permits - Criteria - Time Limits 36.15.217 Waiver of Permit for Emergency Repair or Replacement Sub-Chapters 3 and 4 Reserved Sub-Chapter 5 Floodplain and Floodway Delineations Rule 36.15.501 Floodplain and Floodway Delineation - Data I Used — Hydrological Certainty 36.15.502 Floodway Delineation ' 36.15.503 Public Input on Proposed Designed Floodplains or Floodways ' ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-271 II DEPARTMENT OF NATURAL RESOURCES AND CONSERVATIM ' Rule 36.15.504 Local Government Adjustments to Proposed Floodway Delineation Sub-thapter 6 ' Designated Floodway Minimum Standards Rule 36.15.601 Uses Allowed Without Permits 36.15.602 Uses Requiring Permits ' 36.15.603 Permits for Water Diversions 36.15.604 Minimum Criteria for Permits ' 36.15.605 Prohibited Uses 36.15.606 Permits for Flood Control Work Sub-Chapter 7 ' Flood Fringe Minimum Standards Rule 36.15.701 Allowed Uses 36.15.702 Flood Proofing for Connercial and Industrial Structures 36.15.703 Prohibited Uses Sub-Chapter 8 Designated Floodplain Only Minimum Standards ' Rule 36.15.801 Allowed Uses Where Floodway Not Designated or No Flood Elevations ' Sub-Chapter 9 Flood Proofing Requirements ' Rule 36.15.901 Flood Proofing Requirements for Electrical Systems ' 36.15.902 Flood Proofing Requirements for Heating Systems ' 36.15.903 Flood Proofing Requirements for Plumbing Systems II NEXT PAGE IS 36-275 36-272 7/1/80 ADMINISTRATIVE RULES OF MONTANA 1 1 FLOODPLAIN MANAGEMENT 36.15.101 Sub-Chapter 1 ' Definitions 36.15.t01 DEFINITIONS In addition to the definition of terms contained in , Section 76-5-103, MCA, and unless the context requires otherwise, as used in the Act and in this chapter: (1) "Act" means Title 76, Chapter 5, MCA, as amended. (2) "Alteration" means any change or addition to an artificial obstruction that either increases the size of the artificial obstruction or increases its potential flood hazard. Maintenance of an artificial obstruction is not an alteration. However, the repair, reconstruction, or improvement of an artificial obstruction, the cost of which equals or exceeds 50 percent of the actual cash value of the artificial obstruction either (a) before the improvement is started, or (b) if the artificial obstruction has been damaged and is being restored, before the damage occurred, is an alternation and not maintenance. (3) "Channelization project" means the excavation and construction of an artificial channel for the purpose of diverting the entire flaw of a watercourse or drainway from its established course. (4) "Flood fringe" means that portion of a designated floodplain outside the limits of a designated floodway. (5) "Floodplain," as defined by Section 76-5-103 (11) , MCA, means "the area adjoining the watercourse or drainway which would be covered by the floodwater of a flood of 100-year frequency." (6) "Floodway," as defined by Section 76-5-103(12) , MCA, means the "channel of a watercourse or drainway and those portions of the floodplain adjoining the channel which are reasonably required to carry and discharge the floodwater of any watercourse or drainway. (7) "Permit issuing authority" means the responsible political subdivision, if any, or the Department if there is no responsible political subdivision. (8) "Responsible political subdivision" means a political subdivision that has received Board approval of its adopted land use regulations and enforcement procedures in accordance with Section 76-5-302, MCA, and ARM 36.15.201 through 36.15.204. (9) "Riprap" means stone, rock, concrete block, or analogous material that is placed along the banks or bed of a watercourse or drainway for the purpose of alleviating erosion. (History: Sec. 76-5-208, MCA; IMP, Sec. 76-5-208 and Sec. 76-5-404, MCA; MU, Eff. 9/4/74.) 1 i NEXT PAGE IS 36-277 ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-275 ' 1 ' FLOCDPLAIN MANAGEMENT 36-15.204 Sub-Chapter 2 Regulation and Enforcement ' 36.15. _01 DCAL EIII.AT ai AND E[a tCEMENT If a political subdivision adopts land use regulations that equal or exceed the minimum standards I contained in sub-chapters 6 through 9 of these rules within the time specified and if the administrative and enforcement procedures for such regulations meet the requirements of these rules and are approved by the Board in accordance ' with Section 76-5-302, MCA, no permit will be required from the Department. (History: Sec. 76-5-208, MCA; TMP, Sec. 76-5-302, MCA; NE& Eff. 9/4/74; EMFRO. AND, Eff. 9/4/75.) II I t:.4 WA./ : 4. is : ar,) : •A. :., ENFORCEMENT (1) Copies of all regulations, resolutions, or ordinances proposed to be adopted by a political subdivision to meet the requirements of I the Act and these rules and an explanation of its proposed administrative and enforcement procedures shall be sent to the Department for approval by the Board. (2) The Department will notify the political subdivision by letter of I Board approval or disapproval. (History: Sec. 76-5-208, MCA; TMP, Sec. 76-5-302, MCA; }f, Eff. 9/4/74; EMERO. MQ Eff. 9/4/75.) II 36.15.203 TIME LIMIT FIR ADOPTION OF LOCAL REGULATI After a floodway or a floodplain has been designated by the Board, the Department shall notify the affected political subdivisions and set forth the I date by which the political subdivision must adopt land use regulations in accordance with the Act and these rules. (History: Sec. 76-5-208, MCA; IMP, Sec. 76-5-302, MCA; 1 (, Eff. 9/4/74; EMERG. AMD, Eff. 9/4/75.) II 36.15.204 LOCAL REGULATIONS - REODIREMENTS (1) Land use regulations adopted by a local political subdivision in conformance with the Act and these rules may include zoning, building codes, and subdivision regulations adopted I pursuant to other enabling statutory authority, such as Title 76, Chapters 1 and 3, Title 76, Chapter 2, Part 3, and Title 76, Chapter 2, Parts 1 and 2, MCA, as well as regulations adopted under the authority given in Sections 76-5-404 through 76-5-406, MCA. (2) Any land use regulations and procedures adopted to comply with the Act and these rules must include the following: (a) Permits must be required prior to the establishment of any new artificial obstruction or nonconforming use requiring a permit under the Act or these rules or for the alteration of any existing artificial obstruction; (b) An official must be hired or appointed with the authority. 1 1 ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-277 i i DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION 36.15.204 to review permit applications and proposed uses or construction to determine compliance with the Act, these rules, and the regulations adopted by the political subdivision; (c) Regulations governing the granting of permits must be at least as stringent as the minimum standards contained in these rules; (d) The approval of the Department must be obtained prior to the approval by the political subdivision pursuant to ARM 36. 15.216(3) of any permit application that is in variance with the adopted regulations and these rules; (e) Copies of all permits granted must be sent to the Department; (f) Before the regulations are effective, all known property owners within the designated floodplain and designated floodway must be notified by mail by the political subdivision that their property is located within the designated floodplain or floodway and is subject to regulation. This notification provision shall not apply to political subdivisions that have adopted building codes requiring permits for new construction or to municipalities or counties that have received Flood Hazard Boundary Maps or Flood Insurance Rate Maps from the United States Department of Housing and Urban Development: (g) A disclosure provision requiring all property owners in a designated floodplain or floodway to notify potential buyers or their agents that such property is located within the designated floodplain or floodway and is subject to regulation. (3) the regulations may also incude the following: (a) requirements that existing nonconforming uses be inspec- ted and documented to insure future compliance; (b) the imposition of a reasonable application fee not to exceed $25.00 for the processing of permit applications. (History: Sec. 76-5-208, MCA; ME, Sec. 76-5-302, MCA; NEW, Eff. 9/4/74; EMERG. AMD, Eff. 9/4/75.) 36.15.205 through 36.15.208 Reserved ' 1 1 NEXT PAGE IS 36-281 36-278 7/1/80 ADMINISTRATIVE RULES OF MONTANA i ' FLOODPLAIN MANAGEMENT 36.15.210 ' 36.15.209 DEPARTMENT REIULATION AND ESIFORCF)4E R' (1) If the political subdivision fails to adopt land use regulations that meet or exceed the minimum standards required by the Act and these rules within ' the time specified, the minimum standards set forth in the Act and these rules regulating the designated floodplain or floodway will be enforced by the Department. (2) An application to the Department for a permit shall be made on a Istandard form furnished by the Department (Form 650) and shall include all applicable information listed on the form. (3) The permit to establish or alter artificial obstructions or I nonconforming uses, if approved, will be given by the Department on a standard form (Form 651) . (History: Sec. 76-5-208, MCA; IMP, Sec. 76-5-301, MCA; fl , 9/4/74.) ' 36.15.210 E lVIROt14 TEAL IMPACT STATEMENTS (1) If in the case of a permit application to the Department, the Department is of the opinion that a proposed I alteration, obstruction, or nonconforming use would have a significant impact on the environment, the Department may require the applicant to provide information necessary for the preparation of an Environmental Impact Statement, I pursuant to the Montana Environmental Policy Act, Title 75, Chapter 1, MCA. (2) If an Environmental Impact Statement is required, the Department shall so inform the applicant in writing indicating the information required for I preparation of the Environmental Impact Statement by the Department. (3) A permit application requiring an Environmental Impact Statement will be specifically approved or denied by the Department only after full compliance with the provisions of the Montana Environmental Policy Act. Normally, the I period of time required for review of these permit applications will be from 60 to 120 days. (History: Sec. 76-5-208, MCA; TMP, Sec. 76-5-405, MCA; j, Eff. 9/4/74.) 36.15.211 through 36.15.215 Reserved 1 1 1 1 NEXT PAGE IS 36-285 IADMINISTRATIVE RULES OF MONTANA 7/1/80 36-281 1 I FLOO:WAY MANPGEMENT 36.15.217 36.15.216 PERMITS - CRITERIA - TINL LIMITS (1) Permits shall be ganted or denied by the permit issuing authority on the basis of whether the proposed establishment or alteration of an artifical obstruction or nonconforming use meets the requirements of the Act and the minimum standards established by the Board in these rules. (2) Additional factors that shall be considered for every permit application are: (a) the danger to life and property from backwater or diverted flow caused by the obstruction; (b) the danger that the obstruction will be swept downstream to the injury of others; (c) the availability of alternative locations; (d) the construction or alteration of the obstruction in such manner as to lessen the danger; (e) - the permanence of the obstruction; (f) The anticipated development in the foreseeable future of the area which may be affected by the obstruction; and, (g) such other factors as are in harmony with the purposes of the Act and these rules. (3) The permit issuing authority may grant a permit for the establishment or alteration of an artificial obstruction or nonconforming use that is not in compliance with the minimum standards contained in these rules only if: (a) The proposed use would not increase flood heights or flood hazard either upstream or downstream; (b) Refusal of a permit would because of exceptional circumstances cause a unique or undue hardship on the applicant or community involved; (c) The proposed use is adequately floodproofed; and (d) Reasonable alternative locations outside the designated floodplain are not available. ' (4) A permit application is considered to have been automatically granted 60 days after receipt of the application, unless the permit issuing authority notifies the applicant before the 60th day that the permit is denied unless ARM 36.15.801(3) or 36.15.210 apply. (History: Sec. 76-5-208, MCA; , Sec. 76-5-405 and 76-5-406, MCA; NEw, Eff. 9/4/74.) to • • n MU Pig Dike [34':_I± in i 71tii :. ?V (1) Emergency repair to and/or replacement of severely damaged public transportation facilities, public water and sewer facilities, and flood control works may be authorized and permit requirements waived if: (a) Upon notification and prior to the emergency repair and/or replacement, the permit issuing authority determines that an emergency condition warranting immediate action exists; and (b) The permit issuing authority agrees upon the nature and type of proposed emergency repair and/or replacement. (2) Authorization to undertake emergency repair and/or replacement work may be given verbally if the permit issuing ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-285 i ' DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION 36.15.217 I authority feels that a written authorization would unduly delay the emergency work. Such verbal authorization must be followed by a written authorization ' stating the emergency condition, the type of emergency work agreed upon, and a notation that verbal authorization had been previously given. (History: Sec. 76-5-208, MCA; IMP, Sec. 76-5-405 and Sec. 76-5-406, MCA; M, 9/4/74.) Sub-Chapters 3 and 4 Reserved 1 1 1 1 NEXT PAGE IS 36-297 II36-286 7/1/80 ADMINISTRATIVE RULES OF MONTANA 1 FLOCDNAY MANAGEMENT 36.15.503 Sub-Chapter 5 Floodplain and Floodway Delineations 36.15.501 FLmD .ATN AND F mnwav DELINEATIC 4 - DATA US ) - HYDROLOGICAL CERTAIN'L'Y (1) All floodplain delineation studies, reports, and maps used by the Department and Board to establish designated floodplains shall be based upon a flood of 100-year frequency. (2) Each floodplain delineation study arranged by the Department will, insofar as time and funds permit, include a water surface profile shading the elevation of the flood of 100-year frequency and a suggested designated floodway. (3) The Department will also utilize flood hazard maps and data provided by the U. S. Department of Housing and Urban Development for the Federal flood insurance program as a basis for establishing the designated floodplain and floodway. Such maps will delineate the boundaries of the flood of 100-year frequency but will not generally include flood elevations or floodway data. (4) Designated floodplains established for areas where flood elevations and/or floodway data are lacking shall be regulated in accordance with Rule ARM 36.15.801. (5) As required by Section 76-5-202, MCA, the designation of floodplains and floodways shall be based upon reasonable hydrological certainty. (History: Sec. 76-5-208, MCA; IMP, Sec. 76- 5-201 and Sec. 76-5-202, MCA; NEW, Eff. 9/4/74.) 36.15.502 FTlrCHAY DE1,INEATION (1) The delineations of a designated ' floodway shall be based on the channel of the watercourse or drainway and those portions of the adjoining floodplain which are reasonably required to carry the discharge the flood of 100-year frequency without any theoretical measurable increase in flood heights. (2) In areas having appreciable urban development on the floodplain, the outer boundary lines of the floodway may generally follow the riverward limits of development provided that: (a) The calculated elevation of the flood of 100-year frequency would not be increased more than 0.5 of a foot as a result of the theoretical additional construction of the floodway; (b) Floodway lines are compatible with local land use plans; and, (c) The flood fringe does not contain appreciable areas with flood velocities greater than 3 feet per second or flood depths greater than 3 feet. (History: Sec. 76-5-208, MCA; 1NE Sec. 76-5-201 and Sec. 76-5-202, MCA; BEW, 9/4/74.) 36.15.503 PUBLIC INPUT ON PROPOSED DESIGNATED FLOG:PLAINS OR FLOODWAYa , (1) The department shall at least 3 weeks prior to any hearing held for the purpose of establishing a designated 1 ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-297 1 1 1 • • ' DEPARTMENT OF NATURAL RFSOQRCE,S AND CONSERVATION 36.15.504 ' floodplain or floodway furnish the affected political subdivisions maps and other data showing the proposed designated floodplain or floodway together with a letter requesting the political subdivision to furnish any pertinent data on II flood hazards as required by Section 76-5-201 of the Act. (2) The Department shall also issue news releases at least 3 weeks prior to any hearing requesting the public to submit any available data concerning I flood hazard, flood elevations, or the proposed designated floodplain or floodway.boundaries. (History: Sec. 76-5-208, MCA; M, Sec. 76-5-201,101, Eff. 9/4/74.) ' . 1 14. 4 MM AK4.14. •AID 41 1 1S444 ?k/l Al Y\IG.kit. ?, - to ,I: : b\ (1) After the delineation of a suggested designated floodway by the Department and prior to the public hearing to consider the floodway ' delineations, the Department shall meet with local governmental and planning officials to consider possible adjustments due to local land use consideration. (2) No adjustments in floodway width or location may be made, however, if ' such adjustments would theoretically increase flood heights beyond the permissible limits noted in ARM 36.15.502. (History: Sec. 76-5-208, MCA; la, Sec. 76-5-201 and Sec. 76-5-202, MCA; NEW, 9/4/74.) , 1 i 1 NEXT PAGE IS 36-305 36-298 I7/1/80 ADMINISTRATIVE RULES OF MONTANA i • FLOODWAY MANPGEMENT 36.15.602- Sub-Chapter 6 Designated Floodway Minimum Standards 36.15.601_ USES ALLOWED WITHOUT PERMITS (1) In accordance with Section 76-5-401, MCA, the following open space uses shall be allowed without a permit anywhere within the designated floodway provided that they are not prohibited by any other ordinance or statute and provided that they do not require structures other than portable structures, fill, or permanent storage of materials or equipment: (a) agricultural uses; (b) industrial-commercial uses such as loading areas, parking areas, and emergency landing strips; (c) private and public recreational uses such as golf courses, driving ranges, archery ranges, picnic grounds, boatlaunching ramps, swinming areas, parks, wildlife management and natural areas, game farms, fish hatcheries, shooting preserves, target ranges, trap and skeet ranges, hunting and fishing areas, and hiking and horseback riding trails; (d) forestry, including processing of forest products with portable equipment; and (e) residential uses such as lawns, gardens, parking areas, and play areas. subsection, the (2) In addition to the uses specified in the preceding following uses and their accessories do not in the judgment of the Board endanger health or safety or cause increased flood heights and shall thus be allowed without a permit in the designated floodway: (a) irrigation and livestock supply wells provided that they are located at least 500 feet from domestic water supply wells; and (b) fences, except permanent fences crossing channels. (History: Sec. 76-5-208, MCA; TMP, Sec. 76-5-401, Sec. 76-5-405, and Sec. 76-5-406, MCA; NE& Eff. 9/4/74.) 36.15.602 USES R_FtUTRING PERNLITS In addition to the uses allowed under , ARM 36.15.601, the following nonconforming uses and artificial obstructions may be permitted within the designated floodway subject to the issuance of a permit ' by the permit issuing authority under the conditions set forth in this rule and ARM 36.15.603 and 36.15.604: (1) excavation of material from pits or pools provided that: (a) a buffer strip of undisturbed land of sufficient width to prevent flood flows from channeling into the excavation is left between the edge of the channel and the edge of the excavation; (b) the excavation meets all applicable laws and regulations of other local and state agencies; and 1 1 ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-305 1 DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION (c) excavated mat rial is stockpiled outside the designated floodway; 2 railroads hi hway, and street stream crossings provided that the crossings are designs ed to offer minimal obstruction to flood flow; (3) limited filling for highway, street, and railroad embankments not ' associated with stream crossings provided that: (a) reasonable alternative transportation routes outside the designated floodway are not available; and II (b) such floodway encroachment is located as far from the stream channel as possible; (4) buried or suspended utility transmission lines provided that: I (a) suspended utility transmission lines are designed such that the lowest point of the suspended line is at least 6 feet higher than the elevation of the flood of 100-year frequency; (b) towers and other appurtenant structures are designed and placed to II withstand and offer minimal obstruction to flood flows; and (c) utility transmission lines carrying toxic or flammable materials are buried to a depth at least twice the calculated maximum depth of scour for a ' flood of 100-year frequency. The maximum depth of scour may be determined from any of the accepted hydraulic engineering methods, but the final calculated figure shall be subject to approval by the permit issuing authority; (5) storage of materials and equipment provided that: (a) the material or equipment is not subject to major damage by flooding and is properly anchored to prevent flotation or downstream movement; or, (b) the material or equipment is readily ranovable within the limited time I available after flood warning. Storage of flammable, toxic, or explosive materials shall not be permitted; (6) domestic water supply wells provided that: (a) they are driven or drilled wells located on ground higher than surrounding ground to assure positive drainage from the well; (b) well casings are watertight to a distance of at least 25 feet below the ground surface; (c) water supply and electrical lines have a watertight seal where the lines enter the casing; ' (d) all pumps and electrical lines and equipment are either of the submersible type or are adequately floodproofed; and (e) check valves are installed on main water lines at wells and at all building entry locations; ' (7) buried and sealed vaults for sewage disposal in recreational areas provided that they meet applicable laws and standards administered by the Department of Health and Environmental Sciences; (8) public or private campgrounds provided that: 36-306 7/1/80 ADMINISTRATIVE RULES OF MONTANA I FIAODWAY MANAGEMENT 36.15.603 (a) access roads require only limited fill and do not obstruct or divert flood waters; and, (b) no dwellings or permanent mobile hones are allowed (camp trailers without wheels or towing vehicles or otherwise not quickly movable are considered permanent mobile homes) ; (9) structures accessory to the uses permitted in this subsection such as boat docks, marinas, sheds, permanent fences crossing channels, picnic shelters and tables, and toilets provided that: (a) the structures are not intended for human habitation; (b) the structures will have a low flood damage potential; (c) the structures will insofar as possible be located on ground higher than the surrounding ground and as far from the channel as possible; (d) the structures will be constructed and placed so as to offer a minimal obstruction to flood flows; (e) the structures will be firmly anchored to prevent flotation; and, (f) service facilities within these structures such as electrical, heating, and plumbing facilities are floodproofed in accordance with ARM 36.15.901 through 36.15.903; (10) all other nonconforming uses or artificial obstructions not specifically listed in this subsection or in ARM 36.15.606, not allowed under ARM 36.15.601, and not prohibited under ARM 36.15.605. (History: Sec. 76-5-208, MCA; RIP, Sec. 76-5-404 through 76-5-406, MCA; Mb 9/4/74.) 36.15.603 PERMITS FOR WATER DIVERSIONS (1) As provided in the Montana I Water Use Act of 1973, Sections 85-2-302 and 85-2-402, MCA, all new surface water diversions and changes in place of diversion after July 1, 1973, require permits or approval respectively, from the Department. Within designated floodways, the Department shall review each proposed diversion and change in place of diversion to determine if flood flows may be affected. (2) If it appears that a proposed diversion or change in place of diversion may significantly affect flood flows, the Department may require the applicant to provide additional information and to apply for a permit with the permit issuing authority under Title 76, Chapter 5, MCA, as amended. (3) A permit under Title 76, Chapter 5, MCA, as amended, shall not be granted if in the judgment of the permit issuing authority: (a) the proposed diversion will increase the upstream elevation of the 100-year flood a significant amount (0.5 of a foot or as otherwise determined by the permit issuing authority) ; (b) the proposed diversion is not designed and constructed to minimize potential erosion from a flood of 100-year frequency; and, I I ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-307 I I 1 DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION (c) any permanent diversion structure crossing the full width of the I stream channel is not designed and constructed to safely withstand up to a flood of 100-year frequency. (History: Sec. 76-5-208, MCA; Its, Sec. 76-5-404 I through 75-5-406, MCA; Nii, 9/4/74.) 36.15.604 MINIMUM GITERIA FOR PERMITS In addition to the requirements of ARM 36.15.602 and 36.15.603, a permit shall not be approved for a new I artificial obstruction or nonconforming use under this rule if it will significantly increase the upstream elevation of the flood of 100-year frequency 0.5 of a foot or as otherwise determined by the permit issuing II authority or significantly increase flood velocities. (History: Sec. 76-5-208, MCA; la, Sec. 76-5-404 through 76-5-405, MCA; NW, 9/4/74.) 36.15.605 PROHIBITED USES (1) In accordance with Section 76-5-403, MCA, II the following artificial obstructions and nonconforming uses are prohibited within the designated floodway except as allowed by permit under ARM 36-15-602 I through 36.15.604 and ARM 36.15.606: "(a) a building for living purposes or place of assembly or permanent use by human beings; (b) a structure or excavation that will cause water to be diverted from ' the established floodway, cause erosion, obstruct the natural flow of water, or reduce the carrying capacity of the floodway; (c) the construction or permanent storage of any object subject to I flotation or movement during flood level periods." (2) The following artificial obstructions and nonconforming uses are also prohibited within the designated floodway: (a) mobile hones without wheels or taxing vehicles or otherwise not I readily movable; (b) carmercial buildings; (c) solid waste disposal and soil absorption sewage systems except as ' allowed or approved under the laws and standards ad- ministered by the Department of Health and Environmental Sciences; (d) storage of highly toxic, flammable, or explosive materials. (History: Sec. 76-5-208, MCA; IMP, Sec. 76-5-403 and 76-5-406, MCA; }ThW, Eff. I9/4/74.) 36 15 606 PERMITS FOtt FLT_ CONIIt L VUU(- (1) Since structural flood I control works often significantly obstruct and affect floodway flow capacity, the following flood control measures shall be allowed within designated floodways subject to the issuance of a permit by the permit issuing authority I and to the conditions set forth in this rule: (a) Flood control levees and floodwalls if: (i) the proposed levees and floodwalls are designed and constructed to safely convey a flood of 100-year frequency; i ' 36-308 7/1/80 ADMINISTRATIVE RULES OF MONTANA 1 1 FLOCCWAY MANAGEMENT , 36.15.606 (ii) the cumulative effect of the levees and floodwalls combined with allowable flood fringe encroachments does not increase the unobstructed elevation of a flood of 100-year frequency more than 0.5 of a foot at any point; (b) riprap, except that which is hand placed, if: (i) the riprap is designed to withstand a flood of 100-year frequency; and (ii) the riprap does not increase the elevation of the 100-year frequency; and (iii) the riprap will not increase erosion upstream, downstream, or across stream from the riprap site; (c) channelization projects if they do not significantly increase the magnitude, velocity, or elevation of the flood of 100-year frequency downstream from such projects; (d) dams provided that: (i) they are designed and constructed in accordance with approved safety standards; and (ii) they will not increase flood hazards downstream either through operational procedures or improper hydrologic design. (2) The permit issuing authority may establish either a lower or higher permissible increase in the elevation of the flood of 100-year frequency than that established in subsection (1) (a) (ii) for individual levee projects based on the following criteria: (a) The proposed levees and floodwalls, except those to protect agricultural land only, are constructed at least 3 feet higher than the elevation of a flood of 100-year frequency more than 9.5 of a foot at any point, and (b) The estimated cumulative effect of other reasonably anticipated future permissible uses; and (c) The type and amount of existing flood prone deveelo rent in nothe affected area; (History: Sec. 76-5-208, MCA; , 76-5-406, MCA; Md. 9/4/74.) 1 i NEXT PAGE IS 36-315 ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-309 i 1 ' FIAOOWAY MANPGEMFS]T 36.15.701 Sub-Chapter 7 Flood Fringe Minimum Standards ' 36.t .701 ALL _ (1) All uses allowed in the designated floodway without a permit under ARM 36.15.601 shall also be allowed without a permit in the flood fringe. II (2) All uses allowed in the designated floodway subject to the issuance of a permit under ARM 36.15.602 through 36.15.604 and ARM 36.15.606 shall also be allowed in the flood fringe subject to the issuance of a permit by the permit issuing authority. I (3) In addition, structures including, but not limited to residential, commercial, and industrial structures, and suitable fill shall be allowed by permit from the permit issuing authority within the flood fringe subject to the ' following conditions: (a) Such structures or fill must not be prohibited by any other statute, regulation, ordinance, or resolution; I (b) Such structures or fill must be compatible with local comprehensive plans, if any; (c) Residential structures must be constructed on suitable fill such that the lowest finish floor elevations (including basement) are 2 feet or more ' above the elevation of the flood of 100-year frequency. The fill shall be at an elevation no lower than the elevation of the flood of 100-year frequency and shall extend for at least 15 feet at that elevation beyond the structure in all ' directions. Where existing streets, utilities, or lot dimensions make strict compliance with this provision impossible, the permit issuing authority may authorize through the permit a lesser amount of fill or alternative flood I proofing measures. The responsible political subdivision shall notify the Department and receive its approval prior to approving any lesser fill or alternative flood proofing for residential structures; (d) Commercial and industrial structures must be either constructed on I fill as specified in the preceding subparagraph or be adequately flood proofed up to an elevation no lower than 2 feet above the elevation of the flood of 100-year frequency; ' (e) Roads, streets, highways, and rail lines shall be designed to minimize increases in flood heights. Where failure or interruption of transportation facilities would result in danger to the public health or safety, the facilities shall be located 2 feet above the elevation of the flood of 100-year frequency; (f) Public or private structures and facilities for liquid or solid waste treatment and disposal must be floodproofed to insure that no pollutants enter ' flood waters. These facilities must be allowed and approved under laws and standards administered by the Department of Health and Environmental Sciences prior to any approval given by the permit issuing authority; and ' ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-315 1 DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION ' 36.15.702 (g) Agricultural structures that have a law flood damage potential such as sheds, barns, shelters, and hay and grain storage structures must meet the requirements of ARM 36.15.602 (9) . (History: Sec. 76-5-208, MCA; . +1 E, Sec. 76-5-402, Sec. 76-5-404 through 76-5-406, MCA; BEq, 9/4/74.) • .∎ s..• •y_ xr, •wly); 4 : i, yy, 'ky; c 1t_4; Apt t; a. Flood proofing as required in ARM 36.15.701(3) (d) shall be accomplished in accordance with ARM 36.15.901 through 36.15.903 and shall further include the following: (1) If the structure is designed to allow internal flooding of the lowest floor, use of the floor shall be limited to such uses as parking, loading areas, and storage of equipment or materials not appreciably affected by flood water. Further, the floors and walls shall be designed and constructed of materials resistant to flooding up to an elevation of 2 or more feet above the elevation of the flood of 100-year frequency; and (2) Structures whose lowest floors are used for purposes other than parking, loading or storage of materials resistant to flooding shall be waterproofed up to an elevation no laser than 2 feet above the elevation of the flood of 100 year frequency. waterproofing shall include impermeable membranes or materials for floors and walls and watertight enclosures for all windows, doors, and other openings. These structures shall be designed to withstand the hydrostatic pressures resulting from a flood of 100-year frequency. (History: Sec. 76-5-208, MCA; IMP, Sec. 76-5-402, Sec. 76-5-404 through 76-5-406, MCA; mu, 9/4/74.) 31 15 703 PROHIBITED USES The following artificial obstructions and nonconforming uses are prohibited within the flood fringe: (1) solid waste disposal and soil absorption sewage systems, except as allowed or approved under laws and standards administered by the Department of Health and Environmental Sciences; and (2) storage of highly toxic, flammable, or explosive materials. Storage of petroleum products may be allowed by permit if buried in tightly sealed and constrained containers or if stored on compacted fill at least 2 feet above the elevation of the flood of 100-year frequency. (History: Sec. 76-5-208, MCA; ' IMP, Sec. 76-5-404 through Sec. 76-5-406, MCA; ] , 9/4/74.) i NEXT PAGE IS 36-321 36-316 7/1/80 ADMINISTRATIVE RULES OF MONTANA 1 ' FLOODWAY MANAGEMENT 36.15.801 t Subchapter 8 Designated Floodplain Only Minimum Standards ' : I •. .a' D!•• A). }: _S��.,.4 ,/i J... t 4y?1 r: �.0 0_ ELEVATIONS (1) For those watercourses or drainways in which there is a designated floodplain but not a designated floodway or where no flood I elevations are available, all uses allowed in a designated floodway under ARM 36.15.601 without a permit shall also be allowed without a permit in such designated floodplain. (2) All other uses within the designated floodplain shall require permits I from the permit issuing authority. The following conditions insofar as each is applicable shall be attached to each permit approval: (a) If the elevation of the flood of 100-year frequency is available, II residential structures must be built on compacted fill as specified in ARM 36.15.701(3) (c) . If such elevation is not available, the highest known historical flood elevation may be used to establish fill heights; (b) If the elevation of the flood of 100-year frequency is available, II commercial and industrial structures must meet the flood proofing requirements set forth in ARM 36.15.701 (3) (d) and 36.15.702. If such elevation is not available, the highest known historical flood elevation may be used to establish flood proof in heights; (c) Proposed structures must be anchored to prevent flotation or collapse and must be located as far from stream channels as is practicable; and ' (d) Sanitary sewage systems must be allowed and approved under laws and standards administered by the Department of Health and Environmental Sciences prior to any approval given under these rules. (3) Where a proposed development within such designated floodplain may significantly increase flood velocities or depths, the permit issuing authority may require a permit applicant to furnish additional hydraulic and survey ' information before acting upon the permit application. This information may include, but is not limited to, any of the following: (a) valley cross sections of the watercourse and adjoining floodplain; 19b) certification by a qualified professional engineer that floodproofing ' measures are reasonably adequate to protect against major flood damages; or (c) a hydrologic study documenting probable effect on upstream or downstream property owners. (4) Permits for such proposed developments may be modified or denied if the additional information shows that proposals would increase flood damages to other properties or would cause a threat to the health or safety of its occupants. (History: DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION 1 Sec. 76-5-208, MCA; IMP, Sec. 76-5-402, Sec. 76-5-404 through 76-5-406, MCA; l(, 9/4/74.) ' ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-321 1 FLOCOWAY MANAGEMENT 36.15.903 Sub-Chapter 9 Flood Proofing Requirements • • 1 y 111.1 a:•)) P'. ; 9A P: DkA4• i•( DI DAVE 4 1014?Q All electrical service materials, equipment, and installation for uses permitted with or without a permit in a designated floodplain or floodway shall conform to the following conditions: (1) All incoming power service equipment including all metering equipment, control centers, transformers, distribution and lighting panels, and all other stationary equipment must be located at least 2 feet above the elevation of the flood of 100-year frequency; (2) Portable or movable electrical equipment may be placed belay the elevation of the flood of 100-year frequency provided that the equipment can be disconnected by a single plug and socket assembly of the submersible type; t (3) The main paver service line shall have automatically operated electrical disconnect equipment or manually operated electrical disconnect equipment located at an accessible remote location outside the designated floodplain and above elevation of the flood of 100-year frequency; and (4) All electrical wiring systems installed below the elevation of the flood of 100-year frequency shall be suitable for continuous submergence and may not contain fibrous components. (History: Sec. 76-5-208, MCA; IME, Sec. 76-5-401 through 76-5-402 and Sec. 76-5-404 through 76-5-406, MCA; Eff. 9/4/74.) • • 1 aE Gs4.)!'.d4- iv.: .. h.. Y 'PP Heating systems for allowed and permitted floodplain and floodway uses shall conform to the following conditions: (1) Float operated automatic control valves must be installed in supply lines to gas furnaces so that the fuel supply is automatically shut off when flood waters reach the floor level where the furnaces are located; (2) Manually operated gate valves that can be operated from a location above the elevation of the flood of 100-year frequency shall also be provided in gas supply lines; and (3) Electric heating systems must be installed in accordance with ARM , 36.15.902. (History: Sec. 76-5-208, MCA; /ME, Sec. 76-5-401 through 76-5-402 and Sec. 76-5-404 through 76-5-406, MCA; Eff. 9/4/74.) • • , Sib S:tttI• 4.3 3.14■ iit • 'k4P4 Plumbing systems for allowed and permitted floodplain and floodway uses shall conform to the following conditions: (1) Sewer lines, except those to buried and sealed vaults, must have check valves installed to prevent sewage backup into permitted structures; and (2) All toilet stools, sinks, urinals, and drains must be 1 1 ADMINISTRATIVE RULES OF MONTANA 7/1/80 36-325 1 1 DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION I located such that the lowest point of possible water entry is at least 2 feet above the elevation of the flood of 100-year frequency. (History: Sec. 76-5-208, MCA; IME, Sec. 76-5-401 through 76-5-402 and Sec. 76-5-404 through 76-5-406, MCA; Elf. 9/4/74.) i i i 1 1 1 1 1 1 1 1 1 1 NEXT PAGE IS 36-335 36-326 7/1/80 ADMINISTRATIVE RULES OF MONTANA 1 1 FLOODWAY FRINGE: ' . RESIDENTIAL STRUCTURES FIGURE 1 I CC'4a a4. o� .■. ❑ . I15 FEET En 15 FEET I . LOWEST • FLOOR •• e, • .. ., . a•- BASE FLOOD • .• a••°' CONCRETE FOUNDATION'4'''•o: • 2FEET ELEVATION• r my -� COMPACTED FIL [ ° ORIGINAL GROUND .i,^�W r a c/Ya`avw•e.'w' e , nF;lt'4an J 1 '( }/ V' 4w4 :Yi a ¢ti- +1:21 ..f.•. •_•• ",oaf •4t;;.0 , i•Kt:;.J, , +•,�c°rr. tYF�.nax�Y ..�i CY :�..;��'i<`i .•r;ri'`"• ' ..F !.> .c::k..'• a . .,vt ,.1. 7" . eili,lA{p..• ., art.. IRegulations for Residential Structures 1 ) . The new residential construction , alteration and substantial I improvement must be constructed on suitable fill so that the lowest floor elevation (including basement) is two feet or more above the 13FE. The fill elevation is to be no lower I than the BFE and shall extend for at least 15 feet beyond the structure in all directions . I 2) . Suitable fill is material which is stable, compacted , well graded , pervious , generally unaffected by water and frost , devoid of trash and organic material ; and is fitted for the . purpose of supporting the permanent structure. I3) . It must be anchored to prevent flotation or collapse. Mobile homes must use over-the-top and frame ties at each corner and I additional ties per side at intermediate points. Any additions must be similarly anchored . Normal use of anchor bolts for residential structures is adequate. I4 ) . Adequate surface drainage must be provided. I I ■ I . FLOODPROOFING OF COMMERCIAL OR INDUSTRIAL STRUCTURE TO TWO FEET ABOVE BFE FIGURE 2 1 __ _ice ____ v7;//:,1,/ 4 / //, < x_e •_ .-- am. A owei..t..•,.. •, la . imal ( 4. i . . A� I ://,/,,,,,: ,, ,:,...?„,..;:t., j .Ir ..4i� . . mac / /, /`rt:ry %trt 4__cis _ __,1 ?jk ,I��� i{ rl�� v' I r tir rrY I Y37Y,L. 5 ,. y l t`, i1.�'Al' P'�\lr{11 r�✓.,� .: 4 '��4Fe� .wu�� T Rri�' 3 . r S i�L14fytil.� /I 1 1k w i!' :;;a9411,1.;A t 7 t . t v y t%t. ia4 ' J.T.iri '�' T1 y,1� I k Pil:: ffili n� �r t t • fl l.r' irt%- fl - /cj+� < �r 5 7 r�fCrl . it "tk^a.'111 17:ZII,.. lyy�`Y}1` 4 / �`r rr C yvA k�f:.� 1 4 c . .ii •a. . I 1. Impermeable membranes to two feet above BFE. 2. Valve on sewer line to prevent back flow. 3. Power Service equipment raised to two feet above BFE. ' I 4. Underground storage tank properly anchored. 1 5. Steel bulkheads for doorways. 6. Sump pump and drain to eject seepage. I7. Internal floors and walls made of materials resistant to flood damage to two feet above BFE. 8. Automatic shut-off valves on furnaces and fuel supply lines.