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HomeMy WebLinkAbout005.01 - Appendix E.2 -FloodHazardEvaluationmemo Page 1 TO: Brian Heaston, PE – City of Bozeman Floodplain Administrator FROM: John Heine, PE, CFM DATE: March, 2024 JOB NO.: 6916.00400 RE: Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation CC: File Urgent For Review Please Comment Please Reply For Your Use Introduction Virga Capital contracted with Morrison-Maierle to provide a flood hazard analysis for Phase 1 of the Turnrow Subdivision located just west of Davis Lane and south of E Valley Center Road in Bozeman, MT (45°43'25.28"N, 111° 5'0.57"W). There are no floodplains designated by the Federal Emergency Management Agency (FEMA) (Firm Panel 30031C0802D) in the project area. However, Cattail Creek is located along the east side of the adjacent Davis Lane and runs through the north side of the proposed subdivision. Because of the proximity of Cattail Creek to the subdivision and the size of its watershed (<25 square miles), Section 38.600.150.C of the Bozeman, MT Code of Ordinances apply and a flood hazard evaluation is required for the subdivision. This flood hazard evaluation memo is prepared in accordance with Section 38.600.150.C of the Bozeman, MT Code of Ordinances. Hydrology The City of Bozeman Design Standards and Specification Policy recommended that the Rational Method be used to develop hydrology for projects within the City of Bozeman. However, because the Rational Method is only appropriate for basins less than 200 acres, Morrison-Maierle developed hydrology for the models using the Natural Resources Conservation Service (NRCS) Peak Discharge Method as documented by Chapter 9 of the Montana Department of Transportation (MDT) Hydraulics Manual, dated January 2022. The NRCS recommends the Peak Discharge Method for basins less than 2,000 acres, making it appropriate for this analysis. We delineated the contributing drainage basins for Cattail Creek and an unnamed tributary to Cattail Creek (Figure 1) using a mixture of semi-automated Arc Hydro tools in ArcGIS Pro and manual methods. We used elevation rasters developed from LiDAR flown in 2018 as the basis for the delineation. We received the elevation rasters from the City of Bozeman (City) in August 2023. The storm drain network within the basins was also considered for the delineation. 3/26/24 Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation Page 2 FIGURE 1: CONTRIBUTING DRAINAGE BASINS FOR CATTAIL CREEK AND UNNAMED TRIBUTARY. Morrison-Maierle used rainfall depths from Appendix 9B of Chapter 9 of the MDT Hydraulics Manual. Rainfall depths for the 24-hour storm duration for the Bozeman Airport were used and are shown in Table 1. We used a Type I rainfall distribution as required by the MDT Hydraulics Manual because the 6- hour rainfall divided by the 24-hour rainfall fell between 0.518 and 0.639 for all recurrence intervals. TABLE 1: BOZEMAN AIRPORT 24-HOUR STORM RAINFALL DEPTHS. 24-Hour Storm Rainfall Depths - Bozeman Airport 50% AEP 20% AEP 10% AEP 4.0% AEP 2.0% AEP 1.0% AEP 1.18 1.49 1.7 1.96 2.15 2.34 We developed curve numbers for the basins based on soil characteristics and land cover. We used the Natural Resources Conservation Service’s Web Soil Survey to determine the hydrologic soil group for various soil types within the subbasin and used the City’s future land use map to determine land cover. Curve numbers selected for the basins are summarized in Table 2. Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation Page 3 TABLE 2: CURVE NUMBER SUMMARY Curve Number Summary Cover Description Cattail Creek Unnamed Tributary Area (ac) % of Basin CN (B, C) (1) Area (ac) % of Basin CN (B, C) (1) Commercial and Business Areas 189 12% 92, 94 119 7% 92, 94 Open Space, Good Condition 115 7% 61, 74 118 7% 61, 74 Residential, 1/8 Acre or Less 24 2% 85, 90 17 1% 85, 90 Residential, 1/4 Acre or Less 1057 68% 75, 83 1265 76% 75, 83 Residential, 1 Acre 179 11% 68, 79 149 9% 68, 79 Composite 1564 100% 80 1668 100% 80 (1) B, C refers to soils in hydrologic soil groups B and C, respectively. We developed time of concentration estimates for each basin using the NRCS watershed lag method, which is appropriate for small urban areas less than 2,000 acres. The analysis resulted in a time of concentration of 4.5 hours for Cattail Creek and 4.8 hours for the unnamed tributary. Using the NRCS Peak Discharge Method, Morrison-Maierle estimates the peak flow rates for the 1.0% AEP (100-year) event at 141 cfs for both Cattail Creek and the unnamed tributary. The City of Bozeman requires detention or retention of the 10% AEP (10-year) storm for new development. Because of the detention/retention requirements, the peak runoff for larger storms may also be attenuated to some degree. However, because the detention/retention facilities are likely to be full at the time of peak rainfall during a large event, their effect on the peak runoff rates for larger storms is likely limited. Because we did not consider detention or retention within the basins or significant ponding behind roads for this analysis, estimated peak flow rates are likely conservative. Existing Conditions Model Morrison-Maierle developed an existing conditions model in HEC-RAS v6.2.0. We developed the model with a 2D geometry using a quasi-steady state simulation with the SWE-ELM equation set. Terrain Morrison-Maierle developed terrain data using 2018 elevation rasters received from the City and project survey. All elevation data is georeferenced to the NAD 1983 (2011) RMTCRS Bobcat (Intl Feet) coordinate system (grid coordinates) with elevations referencing the North American Vertical Datum of 1988. Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation Page 4 Geometry Morrison-Maierle developed a 2-dimensional (2D) geometry for the project. We used a mesh with 50- foot cells outside of the area of interest and 10-foot cells for waterways within the area of interest and the riparian zone of Cattail Creek and the unnamed tributary. The 2D mesh extends approximately 600' downstream of the north I90 frontage road to 900' upstream of Westlake Road on Cattail Creek. The existing conditions geometry is shown in Figure 2. Along with Cattail Creek, the 2D mesh also includes an unnamed tributary along the west boundary of the parcel for the proposed subdivision. This tributary divides the proposed subdivision from the Valley Center Subdivision. It does not affect Phase 1 of the subdivision but was included in the model for future phases. FIGURE 2: EXISTING CONDITIONS MODEL GEOMETRY. Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation Page 5 We used breaklines to align cell faces with hydraulic features (roads, natural high terrain, etc) that control the direction of flow. Fourteen 2D Connections represent 19 existing culverts within the mesh. Dimensions of existing culverts were measured on site and the hydraulic structure locations and elevations were surveyed. The following existing hydraulic structures were included for Cattail Creek. 1) North Frontage Road – 48” Reinforced Concrete Pipe (RCP) 2) Railroad – 48” Cast-in-place Concrete Arch 3) Interstate 90 – 42” Corrugated Metal Pipe (CMP) 4) E Valley Center Road – Twin 60” CMP 5) Private Field Drive – 60” CMP 6) Davis Lane – 36” CMP 7) Irrigation Structure north of Westlake Road – 36” CMP and 24” CMP 8) Westlake Road – 42” CMP and 24” CMP 9) Reservoir Outfall south of Westlake Road – 42” CMP The following existing hydraulic structures were included for the unnamed tributary. 1) E Valley Center Road – 48” Reinforced Concrete Pipe (RCP) 2) Private Farm Road – 24” Corrugated Metal Pipe (CMP) We added two upstream boundary conditions to the model geometry. The upstream boundary conditions introduce flow into Cattail Creek and the unnamed tributary at the south boundary of the model. Four downstream boundary conditions use normal depth to determine the water surface elevation at the north boundary of the model. Four downstream boundary conditions were required because of flow splits at E Valley Center Road, I90, a railroad, and north frontage road that convey flow through roadside ditches to the northwest. A sensitivity analysis showed that, in the area of proposed subdivision, the model results are insensitive to reasonable changes in the boundary conditions and they are placed an appropriate distance upstream and downstream of the area of interest. Morrison-Maierle assigned Manning’s roughness values based on the FHWA publication Guide for Selecting Manning's Roughness Coefficients for Natural Channels and Flood Plains. Selected values are shown in Table 3. TABLE 3: MANNING’S ROUGHNESS VALUES. Roughness Sub-Area Type Manning's Roughness Min Max Initial Value Willow Riparian 0.081 0.207 0.090 Grass Riparian 0.041 0.109 0.057 Pasture-Meadow-Hay 0.036 0.103 0.050 Floodplain with Structures 0.057 0.163 0.080 Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation Page 6 A sensitivity analysis showed that the model is insensitive to reasonable changes in Manning’s roughness values. The water surface elevation changes by less than 0.2-feet near critical areas for the 1.0% AEP event when all roughness values are raised by 20%. Selected roughness values are reasonable based on our experience. Simulation The simulation for the existing conditions model uses the SWE-ELM equation set and a computation interval of one second. The simulation runs for six simulated hours, which is sufficient time to completely flood the model and reach quasi-steady state conditions. The existing conditions model results for the 1.0% AEP (100-year) event show that Cattail Creek overtops Westlake Road just east of Davis Lane but remains contained east of Davis Lane until it approaches the sag of Davis Lane just south of E Valley Center Road. At the sag in Davis Lane, Cattail Creek overtops the road and flows along the north side of the proposed subdivision. Existing twin 60” corrugated metal pipes (CMPs) convey the majority of the flow in Cattail Creek north of E Valley Center Road without overtopping the road. North of E Valley Center Road, flow splits multiple times into roadside ditches where it continues north in the channel and northwest in the roadside ditches. The existing twin 60” CMPs create an area of backwater just south of E Valley Center Road to an elevation of 4611.48 feet for the 1.0% AEP event. The elevation of the backwater allows approximately 10 cfs to bypass the culverts and continue flowing northwest on the south side of E Valley Center Road. This flow is conveyed in the south roadside ditch until it converges with flow from the unnamed tributary to the west of the subdivision. The existing conditions model results for the 1.0% AEP (100-year) event show that the unnamed tributary that divides the proposed subdivision from the Valley Center Subdivision has limited capacity to convey flood flows for large events. For the 1.0% AEP event, over 90% of the flow in the unnamed tributary overtops the banks and flows through the easternmost lots of the Valley Center Subdivision. Upstream of E Valley Center Road, the unnamed tributary flow combines with bypass flow from Cattail Creek before overtopping the road. North of E Valley Center Road, the 1.0% AEP event continues to exceed the capacity of the unnamed tributary, flowing through lots of the Lake Subdivision 1 before entering the south roadside ditch of Interstate 90. Existing conditions flooding extents are shown in Figures 3.1 and 3.2. Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation Page 7 FIGURE 3.1: EXISTING CONDITIONS BASE FLOOD ELEVATIONS AND INUNDATION FOR THE UNNAMED TRIBUTARY. FIGURE 3.2: EXISTING CONDITIONS BASE FLOOD ELEVATIONS AND INUNDATION FOR CATTAIL CREEK. Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation Page 8 Proposed Conditions Model Morrison-Maierle developed a proposed conditions model, using a copy of the existing conditions model as a starting point and adding all proposed subdivision improvements. Added improvements included widening Davis Lane south of E Valley Center Road, widening E Valley Center Road, grading for a trail along Cattail Creek at the north end of the proposed subdivision, and mass grading for the subdivision and interior roads (Figure 4). Proposed 60” RCP culverts were added to 2D connections for Quicksilver Road, the trail, and Davis Lane. The culverts include 6” of embedment and entrance loss coefficients of 1.0, the maximum allowed in HEC-RAS, to account for intermediate structures within the culverts for aquatic organism passage (AOP). These culverts were sized to pass the 4% AEP (25-year) event without overtopping with a maximum headwater depth of 1.5 times the culvert diameter. FIGURE 4: PROPOSED CONDITIONS MODEL GEOMETRY. Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation Page 9 Results of the proposed conditions model show that the proposed 60” RCP culverts meet the requirements of the City of Bozeman Design Standards and Specifications Policy for culverts and perform better than the existing in-place infrastructure. The proposed culverts reduce the headwater elevation of Cattail Creek east of Davis Lane when compared to the existing conditions and prevent overtopping of both Davis Lane and Quicksilver Road during the 1.0% (100-year) AEP event (Figure 5). Through the entirety of Phase 1 of the Turnrow Subdivision, Cattail Creek is contained within its channel and floodplain terrace, providing resilience for future development within the subdivision. FIGURE 5: PROPOSED CONDITIONS BASE FLOOD ELEVATIONS AND INUNDATION. Flood Mitigation Because the Cattail Creek channel and floodplain terrace contain all events up to and including the 1.0% AEP event, no flood mitigation is required for the subdivision outside of the culvert construction and mass grading operations. Velocities in the channel are minimal during large events because of the backwater conditions caused by the culverts, so vegetated ditches are sufficient to avoid erosion (Figure 6). Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation Page 10 FIGURE 6: PROPOSED CONDITIONS VELOCITIES. Attachments 1) Basin Delineation Map 2) Existing Conditions BFEs Map 3) Proposed Conditions BFEs Map 4) Proposed Conditions BFE Profile 5) Existing Conditions BFE Profile 6) Hydrologic Calculations 7) NRCS Web Soil Survey Report 8) Hydrologic Analysis Digital Files 9) HEC-RAS Model (Electronic Zip File) 235 CandlelightDrBisonBordLake Dr StubbsLnHiddenValleyRdLakeRWattsLnE Valley Center Rd Chief Joseph Middle School Durston Rd Baxter Ln W Babcock StLaurelPkwy HanleyAveClifden DrW Oak St May Fly StGoochHillRd Bozeman Sports Park Gallatin High School Meadowlark Elementary School T a lo n Way Stucky Rd Stucky RdTexasWayGoochHillRdFallonStRowlandRdCottonwoodRd CottonwoodRdHuffine Ln ChapmanRdChapmanRdBlackwood Rd Patterson RdCottonwoodRdod Balmont 90 NelsonRdCatamount St tta n R d DavisLnFenWayCatron St Red Wing Dr Frontage Rd E Valley C e n t er RdN19thAveWater Reclamation Facility Riverside Country Club Bisel W Babcock St N11thAveAnnie St Annie StN27thAve N15thAveN17thAveW Villard St Ravalli St Lily D r Baxter Ln SandersAveMeagherAveDavisLnN14thAveEquestrian Ln N20thAveValleyDrN19thAveN19thAveDurston Rd W Oak St W Oak StWOakSt W Main St Bozeman High School & Bridger Alternative High School Catron Farmers Ditch S11thAveW Koch St S15thAveKurk DrFowlerAveFallonSt W Graf St Stucky Rd W Lincoln St W Garfield St FowlerLnS11thAveS19thAveS19thAveW Kagy Blvd W College StHuffineLn Gallatin Valley Mall Montana State University Patterson Rd SirArthurDrS3rdRdS19thAveMeadow Creek Patterson Matthews 205 ManleyRdBrid Go Snowfill 205 90 W Babcock StN3rdAve NTracyAveN5thAveNChurchAveNBozemanAveW Curtiss St W Olive StN9thAve NGrandAveNBlackAveNRouseAveN7thAveW Main St Glen Lake Rotary Park Bozeman S3rdAveS3rdAveW Koch St SBlackAveW Dickerson St W Story St W Alderson St Arnold St W Grant St W Kagy Blvd W College St Valley View Go Club Gallagator Linear Burk Goldenstein LnS3rdAveSundance Springs Park \\mmi\share\Bozeman\Projects\6916\004 - Turnrow Preliminary Plat\GIS\TurnrowHydraulicsMap\AMSWorking_Hydrology\AMSWorking_Hydrology.aprx; Plotted: 10/27/2023 COPYRIGHT © MORRISON-MAIERLE, INC., 2023 FIGURE NO. PROJECT NO. MTGALLATIN CO. FIG. 1 6916.004DRAWN BY: AMS CHK'D BY: JCH APPR. BY: JCH DATE: 10/2023 2880 Technology Blvd WBozeman, MT 59718 Phone: (406) 587-0721 TURNROW SUBDIVISION FLOOD HAZARD ANALYSIS BASIN DELINEATION MAP 0 0.65 1.30.33 Miles ³Legend 10 Foot Contours (2018) Rivers and Streams Cattail Creek TOC Flowline W Unnamed Trib TOC Flowline Cattail Creek Watershed West Unnamed Tributary Watershed PAGE 1 of 2 E Valley Center Rd StubbsLnRlane Dr StubbsLn90 90 EValleyCenterRd 205 4611 459 4 4600 4 6 0 2 4604 4608 4604 4603 4601 4624 4599 4603 460246 0 5 4595 46034601 4602 45 9 7 4593 4601 4599 4606 46074614 46004600 4593 4606 460446034608 46014606 460 34600 460546024607 4595 460146004599 46104604 462446004593 4596 4597 4603459946034592 4593 460545 9 2 4610 4609 4594 46064601 4593 45984592 46234604 4599 4600 4625460946074596 4611 4619 460246044605 46104603 46024594 46084593 46004597 4625 4592 461046084602 4612 4605 46054610 46204608 46024596 4608 4603 4595 4595 4622 46084607459 5 4606 4625 4594 4609 45 9 8 461345944603 46134604 4605 4605 4603 4624 46104609 45 9 4 4604 4621 4609 4612 4602 4619 4618 45 9 3 4614 4620 4599 4600 4617 4615 4616 4607 4606 4601 4592 4621 4611 4622 4623 4598 N:\6916\004 - Turnrow Preliminary Plat\GIS\TurnrowHydraulicsMap\AMSWorking_Hydrology\AMSWorking_Hydrology.aprx; Plotted: 3/26/2024 COPYRIGHT © MORRISON-MAIERLE, INC., 2024 FIGURE NO. PROJECT NO. MTGALLATIN CO. FIG. 2.1 6916.004DRAWN BY: AMS CHK'D BY: JCH APPR. BY: JCH DATE: 03/2024 2880 Technology Blvd WBozeman, MT 59718 Phone: (406) 587-0721 TURNROW SUBDIVISION FLOOD HAZARD ANALYSIS EXISTING CONDITIONS BFEs MAP - UNNAMED TRIBUTARY 0 290 580145Feet ³Legend 5 foot Ex. Contours (2018) Ex. Conditions Inundation Map 01pctAEP Ex. BFEs BACKWATERBFE 4598.02 CattailCreekMontanaRailLink 90 E Valley CenterRd Catt ail Cr eek205 90 90 NelsonRdFrontage Rd CattailCreekDavisLnCattailCreekDavisLn46354618 463046114623 4621 4622 4607 461346 0 8 4624 4620 4607 461446 0 8460646084606 461246114608 462846044627 46154607 4631460546194631 463246194626 4632 4623 46304622 4612 461746134616463 4462446154625 463346204621 N:\6916\004 - Turnrow Preliminary Plat\GIS\TurnrowHydraulicsMap\AMSWorking_Hydrology\AMSWorking_Hydrology.aprx; Plotted: 3/26/2024 COPYRIGHT © MORRISON-MAIERLE, INC., 2024 FIGURE NO. PROJECT NO. MTGALLATIN CO. FIG. 2.2 6916.004DRAWN BY: AMS CHK'D BY: JCH APPR. BY: JCH DATE: 03/2024 2880 Technology Blvd WBozeman, MT 59718 Phone: (406) 587-0721 TURNROW SUBDIVISION FLOOD HAZARD ANALYSIS EXISTING CONDITIONS BFEs MAP - CATTAIL CREEK 0 290 580145Feet ³Legend 5 foot Ex. Contours (2018) Ex. Conditions Inundation Map 01pctAEP Ex. BFEs BACKWATER BFE 4620.98 BACKWATERBFE 4611.48 BACKWATERBFE 4632.10 CattailCreekBurlingtonNorthern Railroad 235 235 90 E Valley Center Rd 235 Burlington Northern Railroad 90 CattailCreekDavisLnC attail CreekDavisLn46 0 8 4623 4621 46224613 4624 462 0 460 8 461446064608 4606 461246114608 4627 46 0 84604 4615460746054 6 0 7 46124631 4626 4623 463446224621 463346244625 4632 \\mmi\share\Bozeman\Projects\6916\004 - Turnrow Preliminary Plat\GIS\TurnrowHydraulicsMap\AMSWorking_Hydrology\AMSWorking_Hydrology.aprx; Plotted: 10/27/2023 COPYRIGHT © MORRISON-MAIERLE, INC., 2023 FIGURE NO. PROJECT NO. MTGALLATIN CO. FIG. 3 6916.004DRAWN BY: AMS CHK'D BY: JCH APPR. BY: JCH DATE: 10/2023 2880 Technology Blvd WBozeman, MT 59718 Phone: (406) 587-0721 TURNROW SUBDIVISION FLOOD HAZARD ANALYSIS PROPOSED CONDITIONS BFEs MAP 0 290 580145Feet ³Legend 5 foot Proposed Contours Proposed Condition Inundation Map 01pctAEP Prop. BFEs BACKWATER BFE 4611.5 BACKWATER BFE 4618.11 BACKWATERBFE 4620.66 PHASE 1SUBDIVISIONBOUNDARY \\mmi\share\Bozeman\Projects\6916\004 - Turnrow Preliminary Plat\GIS\TurnrowHydraulicsMap\AMSWorking_Hydrology\AMSWorking_Hydrology.aprx; Plotted: 10/27/2023 COPYRIGHT © MORRISON-MAIERLE, INC., 2023 FIGURE NO. PROJECT NO. MTGALLATIN CO. FIG. 4 6916.004DRAWN BY: AMS CHK'D BY: JCH APPR. BY: JCH DATE: 10/2023 2880 Technology Blvd WBozeman, MT 59718 Phone: (406) 587-0721 TURNROW SUBDIVISION FLOOD HAZARD ANALYSIS PROPOSED BFE PROFILES \\mmi\share\Bozeman\Projects\6916\004 - Turnrow Preliminary Plat\GIS\TurnrowHydraulicsMap\AMSWorking_Hydrology\AMSWorking_Hydrology.aprx; Plotted: 10/27/2023 COPYRIGHT © MORRISON-MAIERLE, INC., 2023 FIGURE NO. PROJECT NO. MTGALLATIN CO. FIG. 5 6916.004DRAWN BY: AMS CHK'D BY: JCH APPR. BY: JCH DATE: 10/2023 2880 Technology Blvd WBozeman, MT 59718 Phone: (406) 587-0721 TURNROW SUBDIVISION FLOOD HAZARD ANALYSIS EXISTING BFE PROFILES 10/12/2023 TurnRow Development SCS TR-55 Hydrology Calculations AMS Method: MDT Hydraulics Manual (Chapter 9, Section 9.8), NRCS TR-55 Peak Discharge Method Basins delineated in GIS with 2018 BZN LiDAR and manual editing based on BZN stormwater layer Tab Key: Name Description Rainfall Rainfall data and distribution type based on BZN Airport Station Soils NRCS soil survey data for sub-basins Land Cover Bozeman future land use layer for sub-basins CN Curve number calculations based on soils and future land use Tc Time of concentration calculation using two different methods: NRCS Watershed Lag Method for Small Urban Areas (9.8.6.2 MDT Manual) and NRCS velocity method (Section 9.8.6.1) Runoff_lag Runoff calculations with Tc based on NRCS small urban area method Runoff_velocity Runoff with Tc based on NRCS velocity method 2-yr 5-yr 10-yr 25-yr 50-yr 100-yr P6 (in)0.71 0.88 0.99 1.14 1.24 1.35 P24 (in)1.18 1.49 1.70 1.96 2.15 2.34 P6/P24 0.602 0.591 0.582 0.582 0.577 0.577 Type I Distribution Recurrence interval Map Unit Symbol Hydrologic Soil Group Map Unit Name Acres in AOI Percent of AOI Map Unit Sum Percent of AOI Redistributed Percentage for 6% N/A 32E Amesha-Trimad complex, 15 to 45 percent slopes B 29.3 0.20% B 37% 40% 32F Amesha loam, 35 to 60 percent slopes B 0.8 0.00% C 57% 60% 50B Blackdog silt loam, 0 to 4 percent slopes C 2,272.30 13.80% N/A 6% 0% 50C Blackdog silt loam, 4 to 8 percent slopes C 286 1.70% 53B Amsterdam silt loam, 0 to 4 percent slopes C 739.8 4.50% Total 100% 53C Amsterdam silt loam, 4 to 8 percent slopes C 75 0.50% 57B Turner loam, 0 to 4 percent slopes B 1,168.10 7.10% 64B Straw loam, 0 to 4 percent slopes B 361.7 2.20% 242E Trimad cobbly loam, 15 to 35 percent slopes B 56.8 0.30% 249A Beaverton cobbly clay loam, 0 to 2 percent slopes B 226.2 1.40% 350B Blackmore silt loam, 0 to 4 percent slopes C 369.3 2.20% 364B Straw silty clay loam, 0 to 4 percent slopes B 298.2 1.80% 407A Sudworth-Nesda loams, 0 to 2 percent slopes B 248.3 1.50% 448A Hyalite-Beaverton complex, moderately wet, 0 to 2 percent slopes C 1,268.80 7.70% 450C Blackdog-Quagle silt loams, 4 to 8 percent slopes C 166 1.00% Turnrow Subdivision AOI USDA Web Soil Survey 450D Blackdog-Brodyk silt loams, 8 to 15 percent slopes C 266.2 1.60% 451C Quagle-Brodyk silt loams, 4 to 8 percent slopes B 41.1 0.30% 451D Quagle-Brodyk silt loams, 8 to 15 percent slopes B 89.2 0.50% 453B Amsterdam-Quagle silt loams, 0 to 4 percent slopes C 207.4 1.30% 453C Amsterdam-Quagle silt loams, 4 to 8 percent slopes C 85 0.50% 453D Amsterdam-Brodyk silt loams, 8 to 15 percent slopes C 83.7 0.50% 457A Turner loam, moderately wet, 0 to 2 percent slopes B 2,160.40 13.10% 506A Saypo silt loam, 0 to 2 percent slopes C 142.3 0.90% 509B Enbar loam, 0 to 4 percent slopes C 689.4 4.20% 510B Meadowcreek loam, 0 to 4 percent slopes C 1,781.50 10.80% 511A Fairway silt loam, 0 to 2 percent slopes C 34.9 0.20% 512B Enbar-Nythar loams, 0 to 4 percent slopes C 84.1 0.50% 514A Soapcreek silty clay loam, 0 to 2 percent slopes D 65.1 0.40% 522A Enbar clay loam, 0 to 2 percent slopes C 592.2 3.60% 537A Lamoose silt loam, 0 to 2 percent slopes B/D 482.2 2.90% 542A Blossberg loam, 0 to 2 percent slopes B/D 594.5 3.60% 556A Threeriv-Bonebasin loams, 0 to 2 percent slopes C/D 68.2 0.40% 606A Bandy-Riverwash- Bonebasin complex, 0 to 2 percent slopes B/D 296.9 1.80% 748A Hyalite-Beaverton complex, 0 to 4 percent slopes C 202.9 1.20% 752E Meagher-Shawmut- Bowery complex, 15 to 45 percent slopes B 15.9 0.10% M-W Water, miscellaneous 8.2 0.10% UL Urban land 863.9 5.30% W Water 7.4 0.00% 16,429.70 100.00%Totals for Area of Interest Converted/Grouped into TR55 Categories Unnamed Creek Unnamed Creek Residential Mixed Use 17 Commercial and business areas 7% Community Commercial Mixed Use 94 Open space (good condition)7% Regional Commercial and Services 25 Residential (1/8 acre or less)1% Public Institutions 149 Residential (1/4 acre avg lot)76% Parks and Open Land 118 Residential (1 acre)9% Urban Neighborhood 1265 100% Cattail Creek Residential Mixed Use 24 Cattail Creek Community Commercial Mixed Use 53 Commercial and business areas 12% Regional Commercial and Services 136 Open space (good condition)7% City of Bozeman future land use layer Public Institutions 179 Residential (1/8 acre or less)2% Parks and Open Land 109 Residential (1/4 acre avg lot)68% Urban Neighborhood 1057 Residential (1 acre)11% Maker Space Mixed Use 6 100% FID Shape *OBJECTID MPMAP DESCRIPTIO Acres Watershed 0 Polygon 5523 RDMU Residential Mixed Use 17 UnnamedCk 1 Polygon 5524 CCMU Community Commercial Mixed Use94UnnamedCk 2 Polygon 5525 RC Regional Commercial and Services25UnnamedCk 3 Polygon 5526 PI Public Institutions 149 UnnamedCk 4 Polygon 5528 POS Parks and Open Land 118 UnnamedCk 5 Polygon 5529 RD Urban Neighborhood 1265 UnnamedCk 0 Polygon 5523 RDMU Residential Mixed Use 24 CattailCk 1 Polygon 5524 CCMU Community Commercial Mixed Use53CattailCk 2 Polygon 5525 RC Regional Commercial and Services122CattailCk 3 Polygon 5526 PI Public Institutions 179 CattailCk 4 Polygon 5528 POS Parks and Open Land 109 CattailCk 5 Polygon 5529 RD Urban Neighborhood 1057 CattailCk 6 Polygon 5530 MSMU Maker Space Mixed Use 6 CattailCk 7 Polygon 5532 RC Regional Commercial and Services14CattailCk B soils C Soils Land Use % of Area Curve Number B Soils Curve Number C Soils Composite CN 40%60%Commercial and business areas 7%92 94 80 Open space (good condition)7%61 74 Residential (1/8 acre or less)1%85 90 Residential (1/4 acre avg lot)76%75 83 Residential (1 acre)9%68 79 B soils C Soils Land Use % of Area Curve Number B Soils Curve Number C Soils Composite CN 40%60%Commercial and business areas 12%92 94 80 Open space (good condition)7%61 74 Residential (1/8 acre or less)2%85 90 Residential (1/4 acre avg lot)68%75 83 Residential (1 acre)11%68 79 Unnamed Creek Cattail Creek Basin Name Description Drainage Area (sq mi) Y Avg Watershed Slope (%)1 Lm (ft)5 Curve Number S Potential max retention (in) tc (hr)2 Ia (in) Unnamed Creek West Unnamed Trib 2.61 4.2 37,950 80 2.6 4.8 0.51 Cattail Creek Cattail Creek 2.44 4.46 37,420 80 2.5 4.5 0.50 Notes:should be between 0.1 and 10 1. Drainage area from watershed boundary shapefile 2. Avg Slope stats from 2018 Raw DEM 3. Lm flow length along thalweg through watershed 4. CN from Land Cover calcs 5. Potential max retention 1000/CN - 10 6. tc calculated using NRCS watershed lag method (MDT Section 9.8.6.2) 7. Ia 0.2*max retention Variable Source 50-pct AEP 20-pct AEP 10-pct AEP 4-pct AEP 2-pct AEP 1-pct AEP 24-hr Precip Depth (in)Appendix 9B-6 1.18 1.49 1.7 1.96 2.15 2.34 Q (direct runoff) (in)EQN 9.8-10 0.14 0.27 0.38 0.52 0.64 0.76 Ia/P Calculated for selecting coefficients 0.43 0.34 0.30 0.26 0.24 0.22 qu (ft3/s/mi2/in)EQN 9.8-11 46 54 61 66 66 71 qp (cfs) EQN 9.8-12 16 38 59 90 110 141 Variable Source 50-pct AEP 20-pct AEP 10-pct AEP 4-pct AEP 2-pct AEP 1-pct AEP 24-hr Precip Depth (in)Appendix 9B-6 1.18 1.49 1.7 1.96 2.15 2.34 Q (direct runoff) (in)EQN 9.8-10 0.15 0.28 0.39 0.54 0.66 0.79 Ia/P Calculated for selecting coefficients 0.42 0.33 0.29 0.25 0.23 0.21 qu (ft3/s/mi2/in)EQN 9.8-11 49 62 62 69 69 74 qp (cfs) EQN 9.8-12 18 43 60 91 111 141 Unnamed Creek Cattail Creek United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Gallatin County Area, MontanaNatural Resources Conservation Service October 27, 2023 Soil Information for All Uses Soil Properties and Qualities The Soil Properties and Qualities section includes various soil properties and qualities displayed as thematic maps with a summary table for the soil map units in the selected area of interest. A single value or rating for each map unit is generated by aggregating the interpretive ratings of individual map unit components. This aggregation process is defined for each property or quality. Soil Qualities and Features Soil qualities are behavior and performance attributes that are not directly measured, but are inferred from observations of dynamic conditions and from soil properties. Example soil qualities include natural drainage, and frost action. Soil features are attributes that are not directly part of the soil. Example soil features include slope and depth to restrictive layer. These features can greatly impact the use and management of the soil. Hydrologic Soil Group Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Custom Soil Resource Report Custom Soil Resource Report Map—Hydrologic Soil Group 5057000505800050590005060000506100050620005063000506400050650005066000506700050570005058000505900050600005061000506200050630005064000506500050660005067000490000 491000 492000 493000 494000 495000 496000 497000 490000 491000 492000 493000 494000 495000 496000 497000 45° 45' 26'' N 111° 8' 3'' W45° 45' 26'' N111° 1' 56'' W45° 39' 47'' N 111° 8' 3'' W45° 39' 47'' N 111° 1' 56'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 12N WGS84 0 2000 4000 8000 12000 Feet 0 500 1000 2000 3000 Meters Map Scale: 1:51,000 if printed on A portrait (8.5" x 11") sheet. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Gallatin County Area, Montana Survey Area Data: Version 27, Aug 25, 2023 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 18, 2022—Aug 29, 2022 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Custom Soil Resource Report Table—Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 32E Amesha-Trimad complex, 15 to 45 percent slopes B 9.9 0.1% 50B Blackdog silt loam, 0 to 4 percent slopes C 2,199.7 20.6% 50C Blackdog silt loam, 4 to 8 percent slopes C 242.3 2.3% 53B Amsterdam silt loam, 0 to 4 percent slopes C 667.0 6.2% 53C Amsterdam silt loam, 4 to 8 percent slopes C 75.0 0.7% 57B Turner loam, 0 to 4 percent slopes B 918.0 8.6% 64B Straw loam, 0 to 4 percent slopes B 340.0 3.2% 242E Trimad cobbly loam, 15 to 35 percent slopes B 49.4 0.5% 249A Beaverton cobbly clay loam, 0 to 2 percent slopes B 142.1 1.3% 364B Straw silty clay loam, 0 to 4 percent slopes B 289.6 2.7% 407A Sudworth-Nesda loams, 0 to 2 percent slopes B 222.9 2.1% 448A Hyalite-Beaverton complex, moderately wet, 0 to 2 percent slopes C 426.8 4.0% 450C Blackdog-Quagle silt loams, 4 to 8 percent slopes C 63.2 0.6% 450D Blackdog-Brodyk silt loams, 8 to 15 percent slopes C 173.7 1.6% 451C Quagle-Brodyk silt loams, 4 to 8 percent slopes B 39.7 0.4% 451D Quagle-Brodyk silt loams, 8 to 15 percent slopes B 68.1 0.6% 453B Amsterdam-Quagle silt loams, 0 to 4 percent slopes C 46.1 0.4% 453C Amsterdam-Quagle silt loams, 4 to 8 percent slopes C 66.2 0.6% Custom Soil Resource Report Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 453D Amsterdam-Brodyk silt loams, 8 to 15 percent slopes C 83.7 0.8% 457A Turner loam, moderately wet, 0 to 2 percent slopes B 1,131.1 10.6% 506A Saypo silt loam, 0 to 2 percent slopes C 130.7 1.2% 509B Enbar loam, 0 to 4 percent slopes C 574.9 5.4% 510B Meadowcreek loam, 0 to 4 percent slopes C 566.2 5.3% 511A Fairway silt loam, 0 to 2 percent slopes C 17.2 0.2% 512B Enbar-Nythar loams, 0 to 4 percent slopes C 35.8 0.3% 514A Soapcreek silty clay loam, 0 to 2 percent slopes D 65.1 0.6% 522A Enbar clay loam, 0 to 2 percent slopes C 504.7 4.7% 537A Lamoose silt loam, 0 to 2 percent slopes B/D 245.7 2.3% 542A Blossberg loam, 0 to 2 percent slopes B/D 206.4 1.9% 556A Threeriv-Bonebasin loams, 0 to 2 percent slopes C/D 32.3 0.3% 606A Bandy-Riverwash- Bonebasin complex, 0 to 2 percent slopes B/D 275.4 2.6% 748A Hyalite-Beaverton complex, 0 to 4 percent slopes C 154.9 1.4% 752E Meagher-Shawmut- Bowery complex, 15 to 45 percent slopes B 12.4 0.1% M-W Water, miscellaneous 5.4 0.1% UL Urban land 611.7 5.7% W Water 5.7 0.1% Totals for Area of Interest 10,699.1 100.0% Rating Options—Hydrologic Soil Group Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Custom Soil Resource Report