CA ERFO FS SEQUI 2021-02(2) Final Hydraulics Memo.pdf

CA ERFO 2021-2(2)

National Forest Service

Powderhorn Bridge

Final Hydraulic Report

Sequoia National Forest Tulare County, California

Prepared for:

U.S. Department of Transportation Federal Highway Administration

Central Federal Lands Highway Division

April 2023

Prepared by:

JACOBS ENGINEERING GROUP, INC.

1501 W Fountainhead Pkwy Suite #401

Tempe, AZ 85282

CA ERFO FS SEQUI 2021-02(2)

i

TABLE OF CONTENTS

I. PROJECT DESCRIPTION AND LOCATION

A. DESCRIPTION

B. LOCATION

II. DRAINAGE BASINS

A. MAJOR BASINS

B. MINOR BASINS

III. DRAINAGE DESIGN CRITERIA

A. GENERAL CRITERIA

B. HYDROLOGIC CRITERIA

C. HYDAULIC CRITERIA

IV. DRAINAGE FACILITY DESIGN

A. HYDROLOGY

B. HYDRAULICS

Modeling Considerations

Modeling Results

C. SCOUR AND BANK PROTECTION

V. REFERENCES

Figures

1 Project Location Map 2 2 Major Basin 3 3 BAER Map 6 4 Cross-Section Map 7

Tables

1 Hydraulic Criteria 4 2 Basin Properties and HEC-HMS Model Input 5 3 Peak Discharges (cfs) 5 4 HEC-RAS Hydraulic Results 9 5 Scour Calculations 10

Appendix

A Proposed Bridge Plans B USGS StreamStats Report for Bear Creek Powderhorn Bridge C NOAA Atlas 14 Precipitation Data D HEC-HMS Model Output E Manning’s ‘n’ Calculation F HEC-RAS Output G Riprap Sizing Calculation H Scour Calculations

I. PROJECT DESCRIPTION AND LOCATION

A. DESCRIPTION

This project is located within the Sequoia National Forest in Tulare County, California, at the Bear Creek crossing of the single lane road 23S64. Bear Creek lies southwest of Johnsondale, CA and flows northeasterly to Double Bunk Creek which lies adjacent to Route M-50.

Bear Creek (looking upstream) Powderhorn Bridge (looking east)

The existing bridge was destroyed in the 2021 summer Windy Fire. It had been constructed in 1958 and is a single lane bridge with length of 32 feet and width of 16 feet. The superstructure was made from timber and has been removed since the fire.

B. LOCATION

The project improvements for this project are located within the boundaries of Sequoia National Forest more specifically in Tulare County, California. Access to the project is by Route M-50 to Route 23S64 at a point southwest of Johnsondale, CA. The project location is at Latitude

35.9528 Longitude -118.5778, as shown in Figure 1.

Figure 1 – Project Location Map

II. DRAINAGE BASINS

A. MAJOR BASINS

The contributing drainage basin has an area of 4.9 square miles and a mean elevation of 6,408 feet. The mean annual precipitation is 35.2 inches. No improvements have been made in the area and the topography was heavily forested before the forest fire. See Figure 2 for watershed delineation.

Figure 2 – Major Basin

B. MINOR BASINS

No minor basins were identified in this drainage analysis.

III. DRAINAGE DESIGN CRITERIA

A. GENERAL CRITERIA

Drainage criteria for the Powderhorn bridge project was generally based on the guidelines outlined in Federal Highway Administration (FHWA) Hydraulic Design Series and United States Forest Service (USFS) Transportation Structures Manual. Other criteria defaults to the Federal Lands Highway Project Development and Design Manual (PDDM). The proposed layout of the new bridge is shown in Appendix A.

B. HYDROLOGIC CRITERIA

The hydrologic criteria for the bridge is the 100-year event.

C. HYDAULIC CRITERIA

Hydraulic design criteria for the project were obtained from the USFS Transportation Structures Handbook and where absent from the Federal Lands Highway Project Development and Design Manual (PDDM) the 23S64 road is classified as a Forest Service Maintenance Level 2 with an average daily traffic of less than 100 vehicles. Based on these parameters, the road is classified as low standard for hydraulic design purposes according to the PDDM. The applicable criteria are listed below. The project site is not located within an effective floodplain delineation per Federal Emergency Management Agency (FEMA) and the Flood Insurance Rate Map (FIRM) panel 06017C2075E has not been printed for the project site.

TABLE 1 - HYDRAULIC CRITERIA

Bridges

Design Frequency

Check Frequency Freeboard

100-year flood N/A

3-feet minimum

Resiliency check for 30-50% debris blockage

50-year flood Greater of 100-year or overtopping

3.5-feet minimum due to potential for woody debris

Scour

Design Frequency

Check Frequency

Countermeasure Design Frequency

100-year flood 200-year flood 200-year flood

Floodplain Encroachment

FEMA SFHA Involvement Allowable Rise

Project outside of FEMA regulated Special Flood Hazard Area (SFHA)

1-foot maximum rise over existing condition

IV. DRAINAGE FACILITY DESIGN

A. HYDROLOGY

Rainfall-runoff modeling using HEC-HMS (US Army Corps of Engineers 2021) was conducted to compare the peak flow estimates from StreamStats. Precipitation values were obtained from NOAA Atlas 14. HEC-HMS models were simulated for the 3-hour storm event based on the watershed drainage area and lag time. Refer to Appendix C for the NOAA Atlas 14 data.

The Natural Resources Conservation Service (NRCS, formerly known as SCS) curve number (CN) method (US Department of Agriculture 1997) was used to estimate runoff using the SCS unit hydrograph method. A composite CN for the basin was estimated using Hydrology Technical Note 4 (US Department of Agriculture 2016) for moderate burn severity. Soils are approximately distributed as 83.6% hydrologic soil group (HSG) A, HSG C 0.7% and 15.7% HSG D. HSG A is characterized as “Low runoff potential and high infiltration rates”. Review of the Burned Area Emergency Response (BAER) burn severity map as shown below suggests that a moderate burn severity is most representative of the watershed. The lower portion of the watershed shows significant severe burn areas; thus, the burn severity was assumed to be between moderate and severe as a conservative measure. The pre-fire CN was estimated to be 48 based on review of the watershed cover and HSG and the post-fire estimated CN was 60. Basin properties and parameters for the HEC-HMS model are summarized in Table 2. HMS input and output is summarized in Appendix D.

TABLE 2 – BASIN PROPERTIES AND HEC-HMS MODEL INPUT

Site

Drainage Area (mi²)

Mean Basin

Elevation (ft)

Mean Basin Slope

Mean Annual Precip

(in)

Curve Number

Longest Flowpath

(ft)

Calculated Lag Time

(min)

Powderhorn Bridge

4.9 6,407 26.9 35.2 60 22,240 94

The StreamStats web application (U.S. Geological Survey 2015) was used to estimate peak discharges. The peak flow result for a 100-year event for the project basin is 764 cubic feet per second (cfs). The regression equation estimates have a standard error of prediction of 54.6 percent for the 100-year return period. The complete results are included in Appendix B.

A review of the USGS National Weather Water Information System (NWIS) found there are no active USGS peak streamflow stations within, near, or downstream of the project limits.

Comparison of these methodologies validated the use of HEC-HMS 100-year value of 959 cfs and was applied in the hydraulic analyses. Table 3 shows a comparison of estimated peak discharges.

TABLE 3 – PEAK DISCHARGES (CFS)

Return Period USGS StreamStats HEC-HMS

2-year 56 1

50-year 568 634

100-year 764 959

200-year 994 1,369

Figure 3 – BAER Map

Note that the 2-year discharge for the HMS model was only 1 cfs. This is likely attributable to the low curve numbers associated with HSG A. For the purposes of hydraulic analysis, the StreamStats value of 56 cfs was used.

B. HYDRAULICS

Flow in Bear Creek was modeled using US Army Corps of Engineers HEC-RAS River Analysis System version 6.3.1.

Modeling Considerations

Model Scenarios

Three conditions were modeled: Existing, Proposed, and Proposed with 30% debris blockage.

The proposed condition consists of the proposed bridge and associated protection.

For the proposed condition, the existing concrete abutments and wingwalls will mostly remain, where the tops will be removed down to an elevation of 5556.75’. The proposed bridge will span over the existing abutments and wingwalls at a length of 48’.

As a resiliency measure, an additional check was performed to account for blockage of conveyance area through the bridge opening due to the potential for woody debris at this location. Blockage in the future from runoff with debris was typically estimated for 30% to 50%.

From field observations, it appeared that 30% blockage would be appropriate to use in a HEC- RAS model. An additional simulation was performed using a 30% reduction in conveyance area by blocking out the area inside the abutments at both bounding cross-sections of the bridge.

Cross-Section Description

One-dimensional cross-sections were placed at key locations along the creek and spaced at approximately 100’ or less. Additional cross-sections were placed in areas of significant topographic change to the creek profile and/or significant changes to the channel shape. Cross-sections were also placed to represent the roadway embankment with the destroyed bridge in the existing condition model and removed and replaced with a bridge structure for the proposed scenarios. Refer to Figure 4 for the cross-section locations.

Figure 4 – Cross-Section Map

Topography was obtained from CFL surveys and converted into a digital terrain model.

Expansion and Contraction Coefficients

The HEC-RAS model was developed with contraction and expansion coefficients of 0.1 / 0.3 for areas outside the immediate influence of the bridge and 0.3 / 0.5 for the bridge, respectively.

These values were selected due to the relatively gradual cross-sectional and flow width variations.

Roughness Coefficients

During the site visit, the channel conditions and overbank conditions were evaluated. The USGS Guide for Selecting Manning’s Roughness Coefficients for Natural Channels and Flood Plains was used. Refer to Appendix E for computations. A Manning’s ‘n’ value of 0.057 was computed for the natural channel and a value of 0.097 for the overbanks.

Reach Boundary Conditions

The Normal Depth slope options were used for both upstream and downstream boundary conditions based on review of the thalweg profile within several hundred feet of the boundaries for each end of the studied stream.

Hydraulic Jump and Drop Analysis

No significant hydraulic jumps or drops exist within the study reach.

Bridges and Culverts

The proposed bridge was modeled in the proposed conditions scenarios using the standard HEC-RAS bridge options including the roadway deck and abutment data to characterize the geometry of the proposed bridge. The existing abutments are proposed to be partially removed from the top down to an elevation of 5,556.75 such that the proposed bridge can span over them for maintenance access.

Levees, Dikes, and Non-Levee embankments

No levees, dikes, or non-levee embankments were modeled as part of this study.

Islands and Flow Splits

No islands or flow splits were modeled as part of this study.

Ineffective Flow Areas

Areas of expansion and contraction were reviewed for a need to implement Ineffective Flow Areas (IFA). IFAs were placed to represent the contraction and expansion of flow at the bridge location.

Blocked Obstructions

No blocked obstructions were modeled as part of this study.

Supercritical Flow

Due to the longitudinal slopes, most flow conditions were subcritical but there were areas where the flows were supercritical. The HEC-RAS model was run for both subcritical and mixed flow regimes.

Subcritical flow results were intended to report worst-case water surface elevations and the mixed flow results were intended to report worst-case velocities and locations of hydraulic jumps.

Modeling Results

Using the Water Surface Elevations (WSE) from the HEC-RAS model and the proposed bridge configuration, compliance with design criteria was confirmed. Freeboard calculations were performed at the upstream bounding cross-section at stream station 523. The controlling point for upstream Section 523 is the southeast corner of the proposed bridge with a low chord elevation of the bridge of 5,559.10. The bridge overtopping elevation at the upstream side is 5,561.83. Freeboard calculations show that the bridge meets criteria as shown in Table 4.

TABLE 4 - HEC-RAS HYDRAULIC RESULTS

Storm Event Q (cfs) U/S XS Station 523 D/S XS Station 485

WSE (ft) Freeboard (ft) WSE (ft) Freeboard (ft)

50-year 634 5,554.58 4.52 5,553.66 5.44

100-year 959 5,555.88 3.22 5,554.76 4.34

100-year (30% Debris Blockage)

959 5,556.77 2.33 5,554.76 4.34

HEC-RAS output including profile plot, cross-section plot, and tabular data is included in Appendix F.

C. SCOUR AND BANK PROTECTION

As shown in the HEC-RAS model, velocities in Bear Creek at the Powderhorn bridge are up to

7.9 feet per second (fps) in the 100-year event. Since the proposed bridge will be placed on drilled shafts extending to rock and the existing abutments will remain, no scour analysis was required. Bedrock below the bridge abutments was encountered at an elevation of approximately 5545’ and extended down to the bottom of available geotechnical borings which terminated at an approximate elevation of 5535’ and is assumed to continue below this elevation.

Contraction and abutment scour calculations were performed for reference and are summarized in Table 5. No evidence of long-term degradation was observed at the bridge site, thus it was not included in the analysis. Scour estimates were performed for the 100-year event and checked with the 200-year event in accordance with the FHWA HEC-18 2012 publication, Evaluating Scour at Bridges. The NCHRP and Froelich’s Equation methods were compared for the abutment scour estimate. The HIRE method for abutment scour estimation was not considered due to the embankment length to depth ratio criteria. Note that the NCHRP abutment scour method includes the Contraction scour depth estimate, thus a total scour elevation estimate using the NCHRP method is set to the thalweg minus the abutment scour. Refer to Appendix H for the scour calculations which were performed using the FHWA hydraulic toolbox software.

The Froelich’s Equation method was used for the scour estimates because it produced more conservative results. The obstruction to flow that the left abutment of the bridge imposes on overbank flows validates the choice to use this method. Estimated scour elevations are above the bedrock elevation, thus no additional scour measures are required for the bridge design.

TABLE 5 – SCOUR CALCULATIONS

Storm Event Q

(cfs) Thalweg

(ft)

Scour Depth (ft) Scour

Elevation (ft) Contraction Abutment

NCHRP Froelich’s

100-year 959 5549.0

0.0 4.1 9.0 5,540.0

200-year (check) 1,369 1.4 6.0 11.1 5,536.5

Riprap bank protection was evaluated as a potential resiliency measure to bolster the abutments.

Riprap sizing was determined using HEC-23 and calculations are documented in Appendix G.

The design conditions are as follows:

Design Storm 100-year Design Discharge 959 cfs Channel Slope 0.0161 ft/ft Channel Bottom Width 28 ft Channel Sideslope 2:1 Riprap Type Crushed Rock

The results indicate the median size, D50, for channel bottom and side slopes is 9 inches, Method B Class II. Due to the favorable bedrock conditions and preservation of the existing concrete abutments, additional riprap protection was not incorporated into the design.

V. REFERENCES

1. Federal Lands Highway, Project Development and Design Manual (PDDM), Federal

Highway Administration, January 2014

2. Guide for Selecting Manning’s Roughness Coefficients for Natural Channels and Flood Plains, Federal Highway Administration, April 1984

3. Pyramid Peaks, 7.5 min. series, Topographic Map, US Geological Survey

4. Federal Highway Administration Hydraulic Design Series No. 2, Highway Hydrology, latest revision

5. HEC-RAS User’s Manual, Hydrologic Engineering Center – US Army Corps of Engineers

6. Highway Design Manual, State of California Department of Transportation, Sixth Edition

7. Federal Highway Administration Hydraulic Engineering Circular No. 23, September 2009

8. Federal Highway Administration Hydraulic Engineering Circular No. 18, April 2012

APPENDIX

Appendix A

Proposed Bridge Plans

Appendix B

USGS StreamStats Report

Bear Creek Powderhorn Bridge Location

Appendix C

NOAA Atlas 14 Precipitation Data

12/20/22, 5:34 PM Precipitation Frequency Data Server https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.9424&lon=-118.5874&data=depth&units=english&series=pds 1/4

NOAA Atlas 14, Volume 6, Version 2 Location name: Springville, California, USA*

Latitude: 35.9424°, Longitude: -118.5874° Elevation: 5799.94 ft**

* source: ESRI Maps ** source: USGS

POINT PRECIPITATION FREQUENCY ESTIMATES

Sanja Perica, Sarah Dietz, Sarah Heim, Lillian Hiner, Kazungu Maitaria, Deborah Martin, Sandra Pavlovic, Ishani Roy, Carl Trypaluk, Dale Unruh, Fenglin Yan, Michael Yekta, Tan Zhao, Geoffrey

Bonnin, Daniel Brewer, Li-Chuan Chen, Tye Parzybok, John Yarchoan

NOAA, National Weather Service, Silver Spring, Maryland

PF_tabular | PF_graphical | Maps_&_aerials

PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1

Duration Average recurrence interval (years)

1 2 5 10 25 50 100 200 500 1000

5-min 0.147 (0.121‑0.181)

0.205 (0.168‑0.252)

0.286 (0.234‑0.353)

0.357 (0.290‑0.445)

0.462 (0.362‑0.594)

0.549 (0.422‑0.722)

0.644 (0.483‑0.867)

0.749 (0.546‑1.04)

0.905 (0.633‑1.31)

1.04 (0.701‑1.55)

10-min 0.211 (0.173‑0.260)

0.293 (0.241‑0.361)

0.410 (0.335‑0.506)

0.512 (0.415‑0.637)

0.662 (0.519‑0.852)

0.787 (0.605‑1.03)

0.923 (0.692‑1.24)

1.07 (0.783‑1.49)

1.30 (0.907‑1.87)

1.49 (1.00‑2.22)

15-min 0.255 (0.210‑0.314)

0.355 (0.291‑0.437)

0.495 (0.405‑0.612)

0.619 (0.502‑0.771)

0.800 (0.628‑1.03)

0.952 (0.731‑1.25)

1.12 (0.837‑1.50)

1.30 (0.947‑1.80)

1.57 (1.10‑2.27)

1.80 (1.22‑2.69)

30-min 0.351 (0.288‑0.432)

0.488 (0.400‑0.601)

0.682 (0.558‑0.842)

0.852 (0.691‑1.06)

1.10 (0.864‑1.42)

1.31 (1.01‑1.72)

1.54 (1.15‑2.07)

1.79 (1.30‑2.48)

2.16 (1.51‑3.12)

2.47 (1.67‑3.70)

60-min 0.492 (0.404‑0.606)

0.684 (0.561‑0.843)

0.956 (0.782‑1.18)

1.19 (0.968‑1.49)

1.54 (1.21‑1.99)

1.84 (1.41‑2.41)

2.15 (1.62‑2.90)

2.51 (1.83‑3.47)

3.03 (2.12‑4.37)

3.47 (2.34‑5.18)

2-hr 0.777 (0.638‑0.956)

1.05 (0.862‑1.29)

1.44 (1.18‑1.78)

1.78 (1.44‑2.22)

2.28 (1.79‑2.94)

2.71 (2.08‑3.56)

3.17 (2.38‑4.27)

3.68 (2.69‑5.10)

4.45 (3.11‑6.42)

5.10 (3.44‑7.62)

3-hr 1.01 (0.831‑1.24)

1.35 (1.11‑1.67)

1.84 (1.50‑2.27)

2.27 (1.84‑2.82)

2.90 (2.27‑3.73)

3.43 (2.63‑4.50)

4.01 (3.00‑5.40)

4.65 (3.39‑6.44)

5.61 (3.93‑8.11)

6.43 (4.35‑9.62)

6-hr 1.51 (1.24‑1.85)

1.99 (1.63‑2.45)

2.69 (2.20‑3.32)

3.30 (2.68‑4.11)

4.20 (3.30‑5.41)

4.96 (3.81‑6.52)

5.79 (4.34‑7.80)

6.71 (4.90‑9.30)

8.09 (5.66‑11.7)

9.25 (6.25‑13.8)

12-hr 2.13 (1.75‑2.62)

2.83 (2.32‑3.48)

3.82 (3.12‑4.72)

4.69 (3.80‑5.84)

5.97 (4.69‑7.69)

7.05 (5.42‑9.26)

8.22 (6.16‑11.1)

9.52 (6.94‑13.2)

11.4 (8.01‑16.5)

13.1 (8.84‑19.5)

24-hr 2.83 (2.54‑3.21)

3.82 (3.43‑4.34)

5.21 (4.67‑5.94)

6.44 (5.72‑7.40)

8.24 (7.08‑9.78)

9.74 (8.20‑11.8)

11.4 (9.34‑14.1)

13.2 (10.5‑16.8)

15.8 (12.2‑21.1)

18.1 (13.4‑24.9)

2-day 3.51 (3.16‑3.98)

4.89 (4.39‑5.56)

6.84 (6.12‑7.79)

8.53 (7.58‑9.80)

11.0 (9.48‑13.1)

13.1 (11.0‑15.9)

15.4 (12.6‑19.1)

17.9 (14.3‑22.9)

21.7 (16.6‑28.8)

24.9 (18.4‑34.2)

3-day 4.00 (3.60‑4.54)

5.69 (5.11‑6.47)

8.05 (7.21‑9.18)

10.1 (8.98‑11.6)

13.1 (11.3‑15.6)

15.7 (13.2‑19.0)

18.4 (15.1‑22.9)

21.5 (17.2‑27.5)

26.1 (20.0‑34.7)

30.0 (22.2‑41.3)

4-day 4.38 (3.94‑4.97)

6.28 (5.64‑7.13)

8.92 (7.99‑10.2)

11.2 (9.96‑12.9)

14.6 (12.5‑17.3)

17.4 (14.6‑21.1)

20.4 (16.8‑25.4)

23.8 (19.0‑30.4)

28.8 (22.1‑38.4)

33.1 (24.5‑45.6)

7-day 5.25 (4.72‑5.97)

7.51 (6.75‑8.54)

10.6 (9.52‑12.1)

13.3 (11.8‑15.3)

17.2 (14.8‑20.4)

20.4 (17.2‑24.8)

23.9 (19.6‑29.7)

27.7 (22.1‑35.4)

33.3 (25.5‑44.3)

38.0 (28.1‑52.3)

10-day 5.93 (5.33‑6.73)

8.43 (7.57‑9.58)

11.9 (10.6‑13.5)

14.8 (13.1‑17.0)

19.0 (16.4‑22.6)

22.5 (18.9‑27.2)

26.2 (21.5‑32.5)

30.2 (24.2‑38.6)

36.1 (27.7‑48.0)

41.0 (30.4‑56.4)

20-day 7.62 (6.85‑8.65)

10.7 (9.59‑12.1)

14.8 (13.2‑16.9)

18.3 (16.2‑21.0)

23.2 (19.9‑27.5)

27.1 (22.8‑32.8)

31.2 (25.7‑38.8)

35.7 (28.5‑45.6)

42.1 (32.3‑56.0)

47.3 (35.1‑65.1)

30-day 9.47 (8.51‑10.8)

13.1 (11.7‑14.9)

17.9 (16.0‑20.4)

21.9 (19.5‑25.2)

27.5 (23.6‑32.6)

31.9 (26.9‑38.7)

36.6 (30.1‑45.4)

41.5 (33.2‑53.0)

48.5 (37.2‑64.6)

54.3 (40.2‑74.7)

45-day 12.1 (10.8‑13.7)

16.4 (14.7‑18.6)

22.0 (19.7‑25.1)

26.6 (23.6‑30.6)

33.0 (28.3‑39.2)

38.0 (32.0‑46.0)

43.1 (35.4‑53.6)

48.6 (38.9‑62.1)

56.3 (43.2‑74.9)

62.5 (46.3‑86.0)

60-day 14.1 (12.7‑16.0)

18.8 (16.9‑21.4)

25.0 (22.4‑28.4)

29.9 (26.6‑34.4)

36.7 (31.6‑43.6)

42.0 (35.3‑50.9)

47.4 (38.9‑58.8)

53.1 (42.4‑67.8)

61.0 (46.8‑81.1)

67.3 (49.9‑92.7)

1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).

Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.

Please refer to NOAA Atlas 14 document for more information.

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PF graphical https://www.commerce.gov/ http://www.noaa.gov/ https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.9424&lon=-118.5874&data=depth&units=english&series=pds 2/4

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Maps & aerials

Small scale terrain https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.9424&lon=-118.5874&data=depth&units=english&series=pds 3/4

Large scale terrain

Large scale map

Large scale aerial

3km

2mi

100km

60mi

100km

60mi https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.9424&lon=-118.5874&data=depth&units=english&series=pds 4/4

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US Department of Commerce National Oceanic and Atmospheric Administration

National Weather Service National Water Center

1325 East West Highway Silver Spring, MD 20910

Questions?: HDSC.Questions@noaa.gov

Disclaimer

100km

60mi https://www.commerce.gov/ http://www.noaa.gov/ http://www.nws.noaa.gov/ https://www.weather.gov/owp/oh mailto:HDSC.Questions@noaa.gov http://www.nws.noaa.gov/disclaimer.html

Appendix D

HEC-HMS Model Output

DATE 12/21/2022

PROJECT CFL - Powderhorn Bridge

SUBJECT Hydrology Calculations

BY JDS

REFERENCE

Method 630.1502 - Watershed Lag Method

Lag Time Input l 22240 ft

Y 26.9 % cn' (CN) 60

S 6.67 in

Lag Time, L 93.9 min

HMS Output - 3hr storm

Q - 50yr 634 cfs

Q - 100yr 959 cfs

Q - 200yr 1369 cfs

Y calculated using USGS 1-second DEM clipped to USGS StreamStats basin polygon, GIS raster slope tool used, reported mean value of 26.9%

(Streamstats reports 26.7%)

USDA NRCS Part 630 Hydrology - National Engineering Handbook - Chapter 15 Time of

Concentration

Appendix E

Manning’s n Calculation

Project: Powderhorn Bridge By:

Subject: HEC-RAS Date:

Manning's Coefficient 'n' Checked:

Jacobs Project No.:

Given: USGS Guide for Selecting Manning's Roughness Coefficients for Natural Channels and Flood Plains n = (nb + n1 + n2+ n3+ n4) x m

Calculations:

Right Overbank nb = Table 1 0.5 mm 0.022 n1 = Table 3 moderate 0.008 n2 = Table 3 not applicable 0.000 n3 = Table 3 minor 0.012 n4 = Table 3 very large 0.055 m = Table 3 minor 1.0 n = 0.097

Channel nb = Table 1 0.5 mm 0.022 n1 = Table 2 severe 0.011 n2 = Table 2 alternating 0.007 n3 = Table 2 minor 0.005 n4 = Table 2 medium 0.012 m = Table 2 minor 1.0 n = 0.057

Left Overbank nb = Table 1 0.5 mm 0.022 n1 = Table 3 moderate 0.008 n2 = Table 3 not applicable 0.000 n3 = Table 3 appreciable 0.012 n4 = Table 3 large 0.055 m = Table 3 minor 1.0 n = 0.097

JPF

10/31/2022

WXYA2204

JDS

Appendix F

HEC-RAS Output

0 200 400 600 800 1000 1200

2023-01-05 Powderhorn Plan: Existing 1/10/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

Bear Creek Powderhorn

2023-01-05 Powderhorn Plan: Existing Mixed 1/10/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

2023-01-05 Powderhorn Plan: Proposed 1/10/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

2023-01-05 Powderhorn Plan: Proposed Mixed 1/10/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

2023-01-05 Powderhorn Plan: Proposed 30pct 1/10/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

2023-01-05 Powderhorn Plan: Proposed 30pct Mixed 1/10/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

HEC-RAS River: Bear Creek Reach: Powderhorn

Reach River Sta Profile Plan Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)

Powderhorn 1091 2yr Ex_sub 56.00 5556.97 5559.06 5559.12 0.004112 1.85 30.34 25.74 0.30

Powderhorn 1091 2yr Ex_mix 56.00 5556.97 5559.06 5558.17 5559.12 0.004112 1.85 30.34 25.74 0.30

Powderhorn 1091 2yr Prop_sub 56.00 5556.97 5559.06 5559.12 0.004112 1.85 30.34 25.74 0.30

Powderhorn 1091 2yr Prop_mix 56.00 5556.97 5559.06 5558.17 5559.12 0.004112 1.85 30.34 25.74 0.30

Powderhorn 1091 2yr Prop_30pct_sub 56.00 5556.97 5559.06 5559.12 0.004112 1.85 30.34 25.74 0.30

Powderhorn 1091 2yr Prop_30pct_mix 56.00 5556.97 5559.06 5558.17 5559.12 0.004112 1.85 30.34 25.74 0.30

Powderhorn 1091 50yr Ex_sub 634.00 5556.97 5562.23 5562.55 0.007647 4.47 141.68 41.03 0.42

Powderhorn 1091 50yr Ex_mix 634.00 5556.97 5562.23 5560.52 5562.55 0.007647 4.47 141.68 41.03 0.42

Powderhorn 1091 50yr Prop_sub 634.00 5556.97 5562.23 5562.55 0.007647 4.47 141.68 41.03 0.42

Powderhorn 1091 50yr Prop_mix 634.00 5556.97 5562.23 5560.52 5562.55 0.007647 4.47 141.68 41.03 0.42

Powderhorn 1091 50yr Prop_30pct_sub 634.00 5556.97 5562.23 5562.55 0.007647 4.47 141.68 41.03 0.42

Powderhorn 1091 50yr Prop_30pct_mix 634.00 5556.97 5562.23 5560.52 5562.55 0.007647 4.47 141.68 41.03 0.42

Powderhorn 1091 100yr Ex_sub 959.00 5556.97 5563.26 5563.68 0.008358 5.17 185.47 44.37 0.44

Powderhorn 1091 100yr Ex_mix 959.00 5556.97 5563.26 5561.25 5563.68 0.008358 5.17 185.47 44.37 0.44

Powderhorn 1091 100yr Prop_sub 959.00 5556.97 5563.26 5563.68 0.008358 5.17 185.47 44.37 0.44

Powderhorn 1091 100yr Prop_mix 959.00 5556.97 5563.26 5561.25 5563.68 0.008358 5.17 185.47 44.37 0.44

Powderhorn 1091 100yr Prop_30pct_sub 959.00 5556.97 5563.27 5563.68 0.008330 5.17 185.66 44.39 0.44

Powderhorn 1091 100yr Prop_30pct_mix 959.00 5556.97 5563.27 5561.25 5563.68 0.008330 5.17 185.66 44.39 0.44

Powderhorn 1091 200yr Ex_sub 1369.00 5556.97 5564.23 5564.79 0.008576 6.01 230.33 48.34 0.46

Powderhorn 1091 200yr Ex_mix 1369.00 5556.97 5564.23 5562.02 5564.79 0.008576 6.01 230.33 48.34 0.46

Powderhorn 1091 200yr Prop_sub 1369.00 5556.97 5564.23 5564.79 0.008581 6.01 230.28 48.33 0.46

Powderhorn 1091 200yr Prop_mix 1369.00 5556.97 5564.23 5562.02 5564.79 0.008581 6.01 230.28 48.33 0.46

Powderhorn 1091 200yr Prop_30pct_sub 1369.00 5556.97 5564.23 5564.79 0.008576 6.01 230.33 48.34 0.46

Powderhorn 1091 200yr Prop_30pct_mix 1369.00 5556.97 5564.23 5562.02 5564.79 0.008576 6.01 230.33 48.34 0.46

Powderhorn 1010 2yr Ex_sub 56.00 5556.85 5557.92 5557.92 5558.26 0.056286 4.67 11.98 18.06 1.01

Powderhorn 1010 2yr Ex_mix 56.00 5556.85 5557.92 5557.92 5558.26 0.056286 4.67 11.98 18.06 1.01

Powderhorn 1010 2yr Prop_sub 56.00 5556.85 5557.92 5557.92 5558.26 0.056286 4.67 11.98 18.06 1.01

Powderhorn 1010 2yr Prop_mix 56.00 5556.85 5557.92 5557.92 5558.26 0.056286 4.67 11.98 18.06 1.01

Powderhorn 1010 2yr Prop_30pct_sub 56.00 5556.85 5557.92 5557.92 5558.26 0.056286 4.67 11.98 18.06 1.01

Powderhorn 1010 2yr Prop_30pct_mix 56.00 5556.85 5557.92 5557.92 5558.26 0.056286 4.67 11.98 18.06 1.01

Powderhorn 1010 50yr Ex_sub 634.00 5556.85 5560.45 5560.21 5561.35 0.032779 7.58 83.63 35.59 0.87

Powderhorn 1010 50yr Ex_mix 634.00 5556.85 5560.45 5560.21 5561.35 0.032779 7.58 83.63 35.59 0.87

Powderhorn 1010 50yr Prop_sub 634.00 5556.85 5560.46 5560.21 5561.35 0.032744 7.58 83.67 35.60 0.87

Powderhorn 1010 50yr Prop_mix 634.00 5556.85 5560.46 5560.21 5561.35 0.032744 7.58 83.67 35.60 0.87

Powderhorn 1010 50yr Prop_30pct_sub 634.00 5556.85 5560.45 5560.21 5561.35 0.032831 7.59 83.58 35.59 0.87

Powderhorn 1010 50yr Prop_30pct_mix 634.00 5556.85 5560.45 5560.21 5561.35 0.032831 7.59 83.58 35.59 0.87

Powderhorn 1010 100yr Ex_sub 959.00 5556.85 5561.19 5560.97 5562.35 0.036717 8.65 110.84 38.65 0.90

Powderhorn 1010 100yr Ex_mix 959.00 5556.85 5561.19 5560.97 5562.35 0.036717 8.65 110.84 38.65 0.90

Powderhorn 1010 100yr Prop_sub 959.00 5556.85 5561.19 5560.97 5562.35 0.036637 8.64 110.93 38.66 0.90

Powderhorn 1010 100yr Prop_mix 959.00 5556.85 5561.19 5560.97 5562.35 0.036637 8.64 110.93 38.66 0.90

Powderhorn 1010 100yr Prop_30pct_sub 959.00 5556.85 5561.17 5560.97 5562.35 0.037338 8.71 110.12 38.58 0.91

Powderhorn 1010 100yr Prop_30pct_mix 959.00 5556.85 5561.17 5560.97 5562.35 0.037338 8.71 110.12 38.58 0.91

Powderhorn 1010 200yr Ex_sub 1369.00 5556.85 5562.04 5561.75 5563.42 0.037556 9.42 145.34 42.06 0.89

Powderhorn 1010 200yr Ex_mix 1369.00 5556.85 5562.04 5561.75 5563.42 0.037556 9.42 145.34 42.06 0.89

Powderhorn 1010 200yr Prop_sub 1369.00 5556.85 5562.04 5561.75 5563.42 0.037515 9.42 145.40 42.07 0.89

Powderhorn 1010 200yr Prop_mix 1369.00 5556.85 5562.04 5561.75 5563.42 0.037515 9.42 145.40 42.07 0.89

Powderhorn 1010 200yr Prop_30pct_sub 1369.00 5556.85 5562.04 5561.75 5563.42 0.037744 9.44 145.06 42.03 0.90

HEC-RAS River: Bear Creek Reach: Powderhorn (Continued)

Reach River Sta Profile Plan Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)

Powderhorn 1010 200yr Prop_30pct_mix 1369.00 5556.85 5562.04 5561.75 5563.42 0.037744 9.44 145.06 42.03 0.90

Powderhorn 932 2yr Ex_sub 56.00 5554.19 5556.16 5555.54 5556.28 0.009808 2.84 19.74 16.54 0.46

Powderhorn 932 2yr Ex_mix 56.00 5554.19 5556.16 5555.54 5556.28 0.009808 2.84 19.74 16.54 0.46

Powderhorn 932 2yr Prop_sub 56.00 5554.19 5556.16 5555.54 5556.28 0.009808 2.84 19.74 16.54 0.46

Powderhorn 932 2yr Prop_mix 56.00 5554.19 5556.16 5555.54 5556.28 0.009808 2.84 19.74 16.54 0.46

Powderhorn 932 2yr Prop_30pct_sub 56.00 5554.19 5556.16 5555.54 5556.28 0.009808 2.84 19.74 16.54 0.46

Powderhorn 932 2yr Prop_30pct_mix 56.00 5554.19 5556.16 5555.54 5556.28 0.009808 2.84 19.74 16.54 0.46

Powderhorn 932 50yr Ex_sub 634.00 5554.19 5558.30 5559.00 0.026952 6.69 94.82 41.04 0.78

Powderhorn 932 50yr Ex_mix 634.00 5554.19 5558.30 5559.00 0.026952 6.69 94.82 41.04 0.78

Powderhorn 932 50yr Prop_sub 634.00 5554.19 5558.30 5559.00 0.026985 6.69 94.78 41.03 0.78

Powderhorn 932 50yr Prop_mix 634.00 5554.19 5558.30 5559.00 0.026985 6.69 94.78 41.03 0.78

Powderhorn 932 50yr Prop_30pct_sub 634.00 5554.19 5558.31 5559.00 0.026838 6.68 94.96 41.04 0.77

Powderhorn 932 50yr Prop_30pct_mix 634.00 5554.19 5558.31 5559.00 0.026838 6.68 94.96 41.04 0.77

Powderhorn 932 100yr Ex_sub 959.00 5554.19 5559.27 5560.05 0.022468 7.07 135.72 43.65 0.71

Powderhorn 932 100yr Ex_mix 959.00 5554.19 5559.27 5560.05 0.022468 7.07 135.72 43.65 0.71

Powderhorn 932 100yr Prop_sub 959.00 5554.19 5559.26 5560.04 0.022605 7.08 135.42 43.63 0.71

Powderhorn 932 100yr Prop_mix 959.00 5554.19 5559.26 5560.04 0.022605 7.08 135.42 43.63 0.71

Powderhorn 932 100yr Prop_30pct_sub 959.00 5554.19 5559.32 5560.07 0.021423 6.95 138.05 43.78 0.69

Powderhorn 932 100yr Prop_30pct_mix 959.00 5554.19 5559.32 5560.07 0.021423 6.95 138.05 43.78 0.69

Powderhorn 932 200yr Ex_sub 1369.00 5554.19 5560.38 5561.23 0.019467 7.36 186.07 46.94 0.65

Powderhorn 932 200yr Ex_mix 1369.00 5554.19 5560.38 5561.23 0.019467 7.36 186.07 46.94 0.65

Powderhorn 932 200yr Prop_sub 1369.00 5554.19 5560.36 5561.21 0.019742 7.40 185.08 46.88 0.66

Powderhorn 932 200yr Prop_mix 1369.00 5554.19 5560.36 5561.21 0.019742 7.40 185.08 46.88 0.66

Powderhorn 932 200yr Prop_30pct_sub 1369.00 5554.19 5560.58 5561.34 0.017149 7.01 195.20 47.56 0.61

Powderhorn 932 200yr Prop_30pct_mix 1369.00 5554.19 5560.58 5561.34 0.017149 7.01 195.20 47.56 0.61

Powderhorn 839 2yr Ex_sub 56.00 5553.23 5554.16 5554.16 5554.40 0.061428 3.99 14.04 28.87 1.01

Powderhorn 839 2yr Ex_mix 56.00 5553.23 5554.16 5554.16 5554.40 0.061428 3.99 14.04 28.87 1.01

Powderhorn 839 2yr Prop_sub 56.00 5553.23 5554.16 5554.16 5554.40 0.061428 3.99 14.04 28.87 1.01

Powderhorn 839 2yr Prop_mix 56.00 5553.23 5554.16 5554.16 5554.40 0.061428 3.99 14.04 28.87 1.01

Powderhorn 839 2yr Prop_30pct_sub 56.00 5553.23 5554.16 5554.16 5554.40 0.061428 3.99 14.04 28.87 1.01

Powderhorn 839 2yr Prop_30pct_mix 56.00 5553.23 5554.16 5554.16 5554.40 0.061428 3.99 14.04 28.87 1.01

Powderhorn 839 50yr Ex_sub 634.00 5553.23 5557.36 5557.66 0.007708 4.42 143.39 49.12 0.46

Powderhorn 839 50yr Ex_mix 634.00 5553.23 5557.36 5557.66 0.007708 4.42 143.39 49.12 0.46

Powderhorn 839 50yr Prop_sub 634.00 5553.23 5557.35 5557.66 0.007736 4.43 143.20 49.10 0.46

Powderhorn 839 50yr Prop_mix 634.00 5553.23 5557.35 5557.66 0.007736 4.43 143.20 49.10 0.46

Powderhorn 839 50yr Prop_30pct_sub 634.00 5553.23 5557.39 5557.68 0.007487 4.38 144.90 49.26 0.45

Powderhorn 839 50yr Prop_30pct_mix 634.00 5553.23 5557.39 5557.68 0.007487 4.38 144.90 49.26 0.45

Powderhorn 839 100yr Ex_sub 959.00 5553.23 5558.45 5558.81 0.007335 4.80 199.93 53.75 0.44

Powderhorn 839 100yr Ex_mix 959.00 5553.23 5558.45 5558.81 0.007335 4.80 199.93 53.75 0.44

Powderhorn 839 100yr Prop_sub 959.00 5553.23 5558.44 5558.80 0.007428 4.82 198.94 53.67 0.44

Powderhorn 839 100yr Prop_mix 959.00 5553.23 5558.44 5558.80 0.007428 4.82 198.94 53.67 0.44

Powderhorn 839 100yr Prop_30pct_sub 959.00 5553.23 5558.58 5558.92 0.006715 4.63 207.00 54.29 0.42

Powderhorn 839 100yr Prop_30pct_mix 959.00 5553.23 5558.58 5558.92 0.006715 4.63 207.00 54.29 0.42

Powderhorn 839 200yr Ex_sub 1369.00 5553.23 5559.65 5560.06 0.007160 5.12 267.20 58.59 0.42

Powderhorn 839 200yr Ex_mix 1369.00 5553.23 5559.65 5560.06 0.007160 5.12 267.20 58.59 0.42

Powderhorn 839 200yr Prop_sub 1369.00 5553.23 5559.61 5560.03 0.007326 5.17 264.80 58.43 0.43

Reach River Sta Profile Plan Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)

Powderhorn 839 200yr Prop_mix 1369.00 5553.23 5559.61 5560.03 0.007326 5.17 264.80 58.43 0.43

Powderhorn 839 200yr Prop_30pct_sub 1369.00 5553.23 5559.98 5560.33 0.005994 4.78 286.67 59.92 0.38

Powderhorn 839 200yr Prop_30pct_mix 1369.00 5553.23 5559.98 5560.33 0.005994 4.78 286.67 59.92 0.38

Powderhorn 755 2yr Ex_sub 56.00 5550.54 5553.08 5553.14 0.003442 1.92 29.13 19.91 0.28

Powderhorn 755 2yr Ex_mix 56.00 5550.54 5553.08 5551.94 5553.14 0.003442 1.92 29.13 19.91 0.28

Powderhorn 755 2yr Prop_sub 56.00 5550.54 5553.08 5553.14 0.003442 1.92 29.13 19.91 0.28

Powderhorn 755 2yr Prop_mix 56.00 5550.54 5553.08 5551.94 5553.14 0.003442 1.92 29.13 19.91 0.28

Powderhorn 755 2yr Prop_30pct_sub 56.00 5550.54 5553.08 5553.14 0.003442 1.92 29.13 19.91 0.28

Powderhorn 755 2yr Prop_30pct_mix 56.00 5550.54 5553.08 5551.94 5553.14 0.003442 1.92 29.13 19.91 0.28

Powderhorn 755 50yr Ex_sub 634.00 5550.54 5556.74 5557.04 0.007159 4.36 145.49 42.87 0.42

Powderhorn 755 50yr Ex_mix 634.00 5550.54 5556.74 5557.04 0.007159 4.36 145.49 42.87 0.42

Powderhorn 755 50yr Prop_sub 634.00 5550.54 5556.73 5557.03 0.007200 4.37 145.17 42.83 0.42

Powderhorn 755 50yr Prop_mix 634.00 5550.54 5556.73 5557.03 0.007200 4.37 145.17 42.83 0.42

Powderhorn 755 50yr Prop_30pct_sub 634.00 5550.54 5556.80 5557.08 0.006863 4.29 147.84 43.12 0.41

Powderhorn 755 50yr Prop_30pct_mix 634.00 5550.54 5556.80 5557.08 0.006863 4.29 147.84 43.12 0.41

Powderhorn 755 100yr Ex_sub 959.00 5550.54 5557.80 5558.18 0.007767 4.96 193.19 47.62 0.43

Powderhorn 755 100yr Ex_mix 959.00 5550.54 5557.80 5558.18 0.007767 4.96 193.19 47.62 0.43

Powderhorn 755 100yr Prop_sub 959.00 5550.54 5557.76 5558.15 0.007926 5.00 191.70 47.48 0.44

Powderhorn 755 100yr Prop_mix 959.00 5550.54 5557.76 5558.15 0.007926 5.00 191.70 47.48 0.44

Powderhorn 755 100yr Prop_30pct_sub 959.00 5550.54 5558.00 5558.35 0.006880 4.72 203.17 48.60 0.41

Powderhorn 755 100yr Prop_30pct_mix 959.00 5550.54 5558.00 5558.35 0.006880 4.72 203.17 48.60 0.41

Powderhorn 755 200yr Ex_sub 1369.00 5550.54 5558.97 5559.43 0.007715 5.44 252.82 53.70 0.43

Powderhorn 755 200yr Ex_mix 1369.00 5550.54 5558.97 5559.43 0.007715 5.44 252.82 53.70 0.43

Powderhorn 755 200yr Prop_sub 1369.00 5550.54 5558.91 5559.38 0.008008 5.51 249.32 53.36 0.44

Powderhorn 755 200yr Prop_mix 1369.00 5550.54 5558.91 5559.38 0.008008 5.51 249.32 53.36 0.44

Powderhorn 755 200yr Prop_30pct_sub 1369.00 5550.54 5559.46 5559.83 0.005930 4.94 279.26 56.23 0.38

Powderhorn 755 200yr Prop_30pct_mix 1369.00 5550.54 5559.46 5559.83 0.005930 4.94 279.26 56.23 0.38

Powderhorn 708 2yr Ex_sub 56.00 5550.30 5552.73 5552.87 0.010359 3.00 18.68 14.48 0.47

Powderhorn 708 2yr Ex_mix 56.00 5550.30 5552.73 5552.87 0.010359 3.00 18.68 14.48 0.47

Powderhorn 708 2yr Prop_sub 56.00 5550.30 5552.73 5552.87 0.010359 3.00 18.68 14.48 0.47

Powderhorn 708 2yr Prop_mix 56.00 5550.30 5552.73 5552.87 0.010359 3.00 18.68 14.48 0.47

Powderhorn 708 2yr Prop_30pct_sub 56.00 5550.30 5552.73 5552.87 0.010359 3.00 18.68 14.48 0.47

Powderhorn 708 2yr Prop_30pct_mix 56.00 5550.30 5552.73 5552.87 0.010359 3.00 18.68 14.48 0.47

Powderhorn 708 50yr Ex_sub 634.00 5550.30 5556.19 5556.56 0.015156 4.89 129.71 46.65 0.52

Powderhorn 708 50yr Ex_mix 634.00 5550.30 5556.19 5556.56 0.015156 4.89 129.71 46.65 0.52

Powderhorn 708 50yr Prop_sub 634.00 5550.30 5556.17 5556.55 0.015389 4.91 129.00 46.59 0.52

Powderhorn 708 50yr Prop_mix 634.00 5550.30 5556.17 5556.55 0.015389 4.91 129.00 46.59 0.52

Powderhorn 708 50yr Prop_30pct_sub 634.00 5550.30 5556.29 5556.64 0.013663 4.71 134.60 47.06 0.49

Powderhorn 708 50yr Prop_30pct_mix 634.00 5550.30 5556.29 5556.64 0.013663 4.71 134.60 47.06 0.49

Powderhorn 708 100yr Ex_sub 959.00 5550.30 5557.28 5557.71 0.013367 5.24 182.94 50.85 0.49

Powderhorn 708 100yr Ex_mix 959.00 5550.30 5557.28 5557.71 0.013367 5.24 182.94 50.85 0.49

Powderhorn 708 100yr Prop_sub 959.00 5550.30 5557.23 5557.67 0.013911 5.32 180.32 50.65 0.50

Powderhorn 708 100yr Prop_mix 959.00 5550.30 5557.23 5557.67 0.013911 5.32 180.32 50.65 0.50

Powderhorn 708 100yr Prop_30pct_sub 959.00 5550.30 5557.59 5557.95 0.010592 4.82 199.12 52.02 0.43

Powderhorn 708 100yr Prop_30pct_mix 959.00 5550.30 5557.59 5557.95 0.010592 4.82 199.12 52.02 0.43

Powderhorn 708 200yr Ex_sub 1369.00 5550.30 5558.53 5559.00 0.011173 5.49 249.74 56.00 0.45

Reach River Sta Profile Plan Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)

Powderhorn 708 200yr Ex_mix 1369.00 5550.30 5558.53 5559.00 0.011173 5.49 249.74 56.00 0.45

Powderhorn 708 200yr Prop_sub 1369.00 5550.30 5558.44 5558.92 0.011999 5.61 244.33 55.33 0.47

Powderhorn 708 200yr Prop_mix 1369.00 5550.30 5558.44 5558.92 0.011999 5.61 244.33 55.33 0.47

Powderhorn 708 200yr Prop_30pct_sub 1369.00 5550.30 5559.16 5559.52 0.007273 4.82 286.09 59.97 0.37

Powderhorn 708 200yr Prop_30pct_mix 1369.00 5550.30 5559.16 5559.52 0.007273 4.82 286.09 59.97 0.37

Powderhorn 660 2yr Ex_sub 56.00 5549.98 5552.42 5552.49 0.005544 2.15 26.05 21.75 0.35

Powderhorn 660 2yr Ex_mix 56.00 5549.98 5552.42 5552.49 0.005544 2.15 26.05 21.75 0.35

Powderhorn 660 2yr Prop_sub 56.00 5549.98 5552.42 5552.49 0.005544 2.15 26.05 21.75 0.35

Powderhorn 660 2yr Prop_mix 56.00 5549.98 5552.42 5552.49 0.005544 2.15 26.05 21.75 0.35

Powderhorn 660 2yr Prop_30pct_sub 56.00 5549.98 5552.42 5552.49 0.005544 2.15 26.05 21.75 0.35

Powderhorn 660 2yr Prop_30pct_mix 56.00 5549.98 5552.42 5552.49 0.005544 2.15 26.05 21.75 0.35

Powderhorn 660 50yr Ex_sub 634.00 5549.98 5555.80 5556.03 0.007099 3.82 166.00 52.92 0.38

Powderhorn 660 50yr Ex_mix 634.00 5549.98 5555.80 5556.03 0.007099 3.82 166.00 52.92 0.38

Powderhorn 660 50yr Prop_sub 634.00 5549.98 5555.78 5556.01 0.007247 3.85 164.76 52.82 0.38

Powderhorn 660 50yr Prop_mix 634.00 5549.98 5555.78 5556.01 0.007247 3.85 164.76 52.82 0.38

Powderhorn 660 50yr Prop_30pct_sub 634.00 5549.98 5555.96 5556.17 0.006215 3.64 174.29 53.58 0.36

Powderhorn 660 50yr Prop_30pct_mix 634.00 5549.98 5555.96 5556.17 0.006215 3.64 174.29 53.58 0.36

Powderhorn 660 100yr Ex_sub 959.00 5549.98 5556.94 5557.21 0.006816 4.19 228.66 57.64 0.37

Powderhorn 660 100yr Ex_mix 959.00 5549.98 5556.94 5557.21 0.006816 4.19 228.66 57.64 0.37

Powderhorn 660 100yr Prop_sub 959.00 5549.98 5556.87 5557.15 0.007148 4.27 224.65 57.35 0.38

Powderhorn 660 100yr Prop_mix 959.00 5549.98 5556.87 5557.15 0.007148 4.27 224.65 57.35 0.38

Powderhorn 660 100yr Prop_30pct_sub 959.00 5549.98 5557.34 5557.56 0.005280 3.81 252.03 59.49 0.33

Powderhorn 660 100yr Prop_30pct_mix 959.00 5549.98 5557.34 5557.56 0.005280 3.81 252.03 59.49 0.33

Powderhorn 660 200yr Ex_sub 1369.00 5549.98 5558.25 5558.55 0.006355 4.44 308.04 63.57 0.36

Powderhorn 660 200yr Ex_mix 1369.00 5549.98 5558.25 5558.55 0.006355 4.44 308.04 63.57 0.36

Powderhorn 660 200yr Prop_sub 1369.00 5549.98 5558.13 5558.45 0.006790 4.56 300.31 63.01 0.37

Powderhorn 660 200yr Prop_mix 1369.00 5549.98 5558.13 5558.45 0.006790 4.56 300.31 63.01 0.37

Powderhorn 660 200yr Prop_30pct_sub 1369.00 5549.98 5559.00 5559.22 0.004098 3.84 358.29 74.75 0.29

Powderhorn 660 200yr Prop_30pct_mix 1369.00 5549.98 5559.00 5559.22 0.004098 3.84 358.29 74.75 0.29

Powderhorn 618 2yr Ex_sub 56.00 5549.87 5551.87 5552.09 0.017410 3.75 14.93 12.27 0.60

Powderhorn 618 2yr Ex_mix 56.00 5549.87 5551.87 5552.09 0.017410 3.75 14.93 12.27 0.60

Powderhorn 618 2yr Prop_sub 56.00 5549.87 5551.88 5552.09 0.017373 3.75 14.94 12.28 0.60

Powderhorn 618 2yr Prop_mix 56.00 5549.87 5551.88 5552.09 0.017373 3.75 14.94 12.28 0.60

Powderhorn 618 2yr Prop_30pct_sub 56.00 5549.87 5551.88 5552.09 0.017373 3.75 14.94 12.28 0.60

Powderhorn 618 2yr Prop_30pct_mix 56.00 5549.87 5551.88 5552.09 0.017373 3.75 14.94 12.28 0.60

Powderhorn 618 50yr Ex_sub 634.00 5549.87 5555.05 5555.55 0.017747 5.71 111.08 43.70 0.63

Powderhorn 618 50yr Ex_mix 634.00 5549.87 5555.05 5555.55 0.017747 5.71 111.08 43.70 0.63

Powderhorn 618 50yr Prop_sub 634.00 5549.87 5554.98 5555.51 0.019005 5.87 108.04 43.30 0.65

Powderhorn 618 50yr Prop_mix 634.00 5549.87 5554.98 5555.51 0.019005 5.87 108.04 43.30 0.65

Powderhorn 618 50yr Prop_30pct_sub 634.00 5549.87 5555.39 5555.78 0.012951 5.01 126.45 45.77 0.53

Powderhorn 618 50yr Prop_30pct_mix 634.00 5549.87 5555.39 5555.78 0.012951 5.01 126.45 45.77 0.53

Powderhorn 618 100yr Ex_sub 959.00 5549.87 5556.30 5556.79 0.014080 5.63 170.30 50.90 0.54

Powderhorn 618 100yr Ex_mix 959.00 5549.87 5556.30 5556.79 0.014080 5.63 170.30 50.90 0.54

Powderhorn 618 100yr Prop_sub 959.00 5549.87 5556.16 5556.69 0.015777 5.87 163.37 50.24 0.57

Powderhorn 618 100yr Prop_mix 959.00 5549.87 5556.16 5556.69 0.015777 5.87 163.37 50.24 0.57

Powderhorn 618 100yr Prop_30pct_sub 959.00 5549.87 5556.92 5557.27 0.008427 4.73 202.61 53.94 0.42

Reach River Sta Profile Plan Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)

Powderhorn 618 100yr Prop_30pct_mix 959.00 5549.87 5556.92 5557.27 0.008427 4.73 202.61 53.94 0.42

Powderhorn 618 200yr Ex_sub 1369.00 5549.87 5557.72 5558.21 0.009804 5.59 244.90 57.88 0.46

Powderhorn 618 200yr Ex_mix 1369.00 5549.87 5557.72 5558.21 0.009804 5.59 244.90 57.88 0.46

Powderhorn 618 200yr Prop_sub 1369.00 5549.87 5557.54 5558.07 0.011032 5.82 235.29 56.89 0.49

Powderhorn 618 200yr Prop_mix 1369.00 5549.87 5557.54 5558.07 0.011032 5.82 235.29 56.89 0.49

Powderhorn 618 200yr Prop_30pct_sub 1369.00 5549.87 5558.68 5559.01 0.005621 4.60 297.90 84.21 0.35

Powderhorn 618 200yr Prop_30pct_mix 1369.00 5549.87 5558.68 5559.01 0.005621 4.60 297.90 84.21 0.35

Powderhorn 586 2yr Ex_sub 56.00 5549.64 5551.52 5551.64 0.010731 2.71 20.64 20.09 0.47

Powderhorn 586 2yr Ex_mix 56.00 5549.64 5551.52 5551.64 0.010731 2.71 20.64 20.09 0.47

Powderhorn 586 2yr Prop_sub 56.00 5549.64 5551.53 5551.64 0.010647 2.71 20.70 20.11 0.47

Powderhorn 586 2yr Prop_mix 56.00 5549.64 5551.53 5551.64 0.010647 2.71 20.70 20.11 0.47

Powderhorn 586 2yr Prop_30pct_sub 56.00 5549.64 5551.53 5551.64 0.010633 2.70 20.71 20.12 0.47

Powderhorn 586 2yr Prop_30pct_mix 56.00 5549.64 5551.53 5551.64 0.010633 2.70 20.71 20.12 0.47

Powderhorn 586 50yr Ex_sub 634.00 5549.64 5555.00 5555.18 0.005066 3.42 185.44 70.20 0.36

Powderhorn 586 50yr Ex_mix 634.00 5549.64 5555.00 5555.18 0.005066 3.42 185.44 70.20 0.36

Powderhorn 586 50yr Prop_sub 634.00 5549.64 5554.92 5555.11 0.005542 3.52 180.05 69.77 0.38

Powderhorn 586 50yr Prop_mix 634.00 5549.64 5554.92 5555.11 0.005542 3.52 180.05 69.77 0.38

Powderhorn 586 50yr Prop_30pct_sub 634.00 5549.64 5555.38 5555.52 0.003442 3.01 210.69 72.19 0.30

Powderhorn 586 50yr Prop_30pct_mix 634.00 5549.64 5555.38 5555.52 0.003442 3.01 210.69 72.19 0.30

Powderhorn 586 100yr Ex_sub 959.00 5549.64 5556.31 5556.50 0.003534 3.48 275.28 77.06 0.31

Powderhorn 586 100yr Ex_mix 959.00 5549.64 5556.31 5556.50 0.003534 3.48 275.28 77.06 0.31

Powderhorn 586 100yr Prop_sub 959.00 5549.64 5556.17 5556.37 0.003937 3.61 265.47 76.39 0.33

Powderhorn 586 100yr Prop_mix 959.00 5549.64 5556.17 5556.37 0.003937 3.61 265.47 76.39 0.33

Powderhorn 586 100yr Prop_30pct_sub 959.00 5549.64 5556.95 5557.09 0.002261 2.99 320.33 80.12 0.25

Powderhorn 586 100yr Prop_30pct_mix 959.00 5549.64 5556.95 5557.09 0.002261 2.99 320.33 80.12 0.25

Powderhorn 586 200yr Ex_sub 1369.00 5549.64 5557.77 5557.97 0.002753 3.60 380.32 84.38 0.28

Powderhorn 586 200yr Ex_mix 1369.00 5549.64 5557.77 5557.97 0.002753 3.60 380.32 84.38 0.28

Powderhorn 586 200yr Prop_sub 1369.00 5549.64 5557.59 5557.81 0.003095 3.73 367.15 83.41 0.29

Powderhorn 586 200yr Prop_mix 1369.00 5549.64 5557.59 5557.81 0.003095 3.73 367.15 83.41 0.29

Powderhorn 586 200yr Prop_30pct_sub 1369.00 5549.64 5558.73 5558.87 0.001565 3.04 451.97 113.15 0.22

Powderhorn 586 200yr Prop_30pct_mix 1369.00 5549.64 5558.73 5558.87 0.001565 3.04 451.97 113.15 0.22

Powderhorn 537 2yr Ex_sub 56.00 5549.00 5551.07 5551.17 0.008381 2.51 22.29 20.10 0.42

Powderhorn 537 2yr Ex_mix 56.00 5549.00 5551.07 5551.17 0.008381 2.51 22.29 20.10 0.42

Powderhorn 537 2yr Prop_sub 56.00 5549.00 5551.08 5551.18 0.008070 2.48 22.60 20.23 0.41

Powderhorn 537 2yr Prop_mix 56.00 5549.00 5551.08 5551.18 0.008070 2.48 22.60 20.23 0.41

Powderhorn 537 2yr Prop_30pct_sub 56.00 5549.00 5551.08 5551.18 0.008137 2.49 22.53 20.20 0.41

Powderhorn 537 2yr Prop_30pct_mix 56.00 5549.00 5551.08 5551.18 0.008137 2.49 22.53 20.20 0.41

Powderhorn 537 50yr Ex_sub 634.00 5549.00 5554.72 5554.94 0.004658 3.73 170.16 89.44 0.36

Powderhorn 537 50yr Ex_mix 634.00 5549.00 5554.72 5554.94 0.004658 3.73 170.16 89.44 0.36

Powderhorn 537 50yr Prop_sub 634.00 5549.00 5554.70 5554.87 0.004102 3.37 188.15 89.29 0.34

Powderhorn 537 50yr Prop_mix 634.00 5549.00 5554.70 5554.87 0.004102 3.37 188.15 89.29 0.34

Powderhorn 537 50yr Prop_30pct_sub 634.00 5549.00 5555.24 5555.37 0.002547 2.86 222.04 92.47 0.27

Powderhorn 537 50yr Prop_30pct_mix 634.00 5549.00 5555.24 5555.37 0.002547 2.86 222.04 92.47 0.27

Powderhorn 537 100yr Ex_sub 959.00 5549.00 5556.07 5556.31 0.004017 3.95 242.84 98.73 0.34

Powderhorn 537 100yr Ex_mix 959.00 5549.00 5556.07 5556.31 0.004017 3.95 242.84 98.73 0.34

Powderhorn 537 100yr Prop_sub 959.00 5549.00 5556.00 5556.19 0.003320 3.54 270.95 98.18 0.31

Reach River Sta Profile Plan Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)

Powderhorn 537 100yr Prop_mix 959.00 5549.00 5556.00 5556.19 0.003320 3.54 270.95 98.18 0.31

Powderhorn 537 100yr Prop_30pct_sub 959.00 5549.00 5556.85 5556.98 0.001946 2.93 327.82 105.44 0.24

Powderhorn 537 100yr Prop_30pct_mix 959.00 5549.00 5556.85 5556.98 0.001946 2.93 327.82 105.44 0.24

Powderhorn 537 200yr Ex_sub 1369.00 5549.00 5557.54 5557.81 0.003573 4.16 329.12 111.25 0.31

Powderhorn 537 200yr Ex_mix 1369.00 5549.00 5557.54 5557.81 0.003573 4.16 329.12 111.25 0.31

Powderhorn 537 200yr Prop_sub 1369.00 5549.00 5557.45 5557.66 0.002836 3.71 369.23 110.48 0.28

Powderhorn 537 200yr Prop_mix 1369.00 5549.00 5557.45 5557.66 0.002836 3.71 369.23 110.48 0.28

Powderhorn 537 200yr Prop_30pct_sub 1369.00 5549.00 5558.65 5558.79 0.001566 3.01 455.15 133.75 0.21

Powderhorn 537 200yr Prop_30pct_mix 1369.00 5549.00 5558.65 5558.79 0.001566 3.01 455.15 133.75 0.21

Powderhorn 523 2yr Ex_sub 56.00 5548.92 5550.93 5551.04 0.009240 2.72 20.59 17.67 0.44

Powderhorn 523 2yr Ex_mix 56.00 5548.92 5550.93 5551.04 0.009240 2.72 20.59 17.67 0.44

Powderhorn 523 2yr Prop_sub 56.00 5548.92 5550.95 5550.34 5551.06 0.008795 2.67 20.98 17.83 0.43

Powderhorn 523 2yr Prop_mix 56.00 5548.92 5550.95 5550.34 5551.06 0.008795 2.67 20.98 17.83 0.43

Powderhorn 523 2yr Prop_30pct_sub 56.00 5548.92 5550.95 5550.34 5551.06 0.008864 2.68 20.91 17.80 0.44

Powderhorn 523 2yr Prop_30pct_mix 56.00 5548.92 5550.95 5550.34 5551.06 0.008864 2.68 20.91 17.80 0.44

Powderhorn 523 50yr Ex_sub 634.00 5548.92 5554.53 5554.85 0.007234 4.53 139.95 91.47 0.44

Powderhorn 523 50yr Ex_mix 634.00 5548.92 5554.53 5554.85 0.007234 4.53 139.95 91.47 0.44

Powderhorn 523 50yr Prop_sub 634.00 5548.92 5554.58 5552.94 5554.81 0.005318 3.84 164.95 92.06 0.38

Powderhorn 523 50yr Prop_mix 634.00 5548.92 5554.58 5552.94 5554.81 0.005318 3.84 164.95 92.06 0.38

Powderhorn 523 50yr Prop_30pct_sub 634.00 5548.92 5555.16 5552.94 5555.32 0.003213 3.24 195.78 98.31 0.30

Powderhorn 523 50yr Prop_30pct_mix 634.00 5548.92 5555.16 5552.94 5555.32 0.003213 3.24 195.78 98.31 0.30

Powderhorn 523 100yr Ex_sub 959.00 5548.92 5555.87 5556.23 0.006186 4.84 198.22 105.43 0.41

Powderhorn 523 100yr Ex_mix 959.00 5548.92 5555.87 5556.23 0.006186 4.84 198.22 105.43 0.41

Powderhorn 523 100yr Prop_sub 959.00 5548.92 5555.88 5553.54 5556.14 0.004357 4.09 234.42 105.53 0.35

Powderhorn 523 100yr Prop_mix 959.00 5548.92 5555.88 5553.54 5556.14 0.004357 4.09 234.42 105.53 0.35

Powderhorn 523 100yr Prop_30pct_sub 959.00 5548.92 5556.77 5553.54 5556.95 0.002500 3.37 284.23 113.32 0.27

Powderhorn 523 100yr Prop_30pct_mix 959.00 5548.92 5556.77 5553.54 5556.95 0.002500 3.37 284.23 113.32 0.27

Powderhorn 523 200yr Ex_sub 1369.00 5548.92 5557.33 5557.74 0.005521 5.14 266.20 117.94 0.38

Powderhorn 523 200yr Ex_mix 1369.00 5548.92 5557.33 5557.74 0.005521 5.14 266.20 117.94 0.38

Powderhorn 523 200yr Prop_sub 1369.00 5548.92 5557.32 5554.20 5557.61 0.003774 4.34 315.43 117.85 0.33

Powderhorn 523 200yr Prop_mix 1369.00 5548.92 5557.32 5554.20 5557.61 0.003774 4.34 315.43 117.85 0.33

Powderhorn 523 200yr…