CA ERFO FS ELDOR 2021-02(4) Hydraulic Memo.pdf

CA ERFO 2021-2(4)

National Forest Service

Alder Creek Bridge

Final Hydraulic Report

Eldorado National Forest Eldorado 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 ELDOR 2021-2(4)

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) 6 4 HEC-RAS Hydraulic Results 9 5 Scour Calculations 10

Appendix

A Proposed Bridge Plans B USGS StreamStats Report for Alder Creek Bridge C USGS StreamStats Report for Alder Creek Gage # 11440000 D NOAA Atlas 14 Precipitation Data E HEC-HMS Model Output F Manning’s ‘n’ Calculation G HEC-RAS Output H Riprap Sizing Calculation I Scour Calculations

I. PROJECT DESCRIPTION AND LOCATION

A. DESCRIPTION

This project is located within the Eldorado National Forest in Eldorado County, California, at the Alder Creek crossing of the single lane road 11N46. Alder Creek lies northwest of Silver Lake and flows northwesterly to the South Fork American River which lies adjacent to US Route 50.

Alder Creek Bridge (looking north) Alder Creek (looking upstream)

The existing bridge was destroyed in the recent Caldor Fire. It had been constructed in 1966 and was a single lane bridge with length of 50 feet and width of 15 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 Eldorado National Forest more specifically in Eldorado County, California. Access to the project is by US 50 to Sly Park Road to Mormon Immigrant Trail (10N50) to 11N46 and 2.5 miles to the project. The project location is at Latitude 38.6887 Longitude -120.3032, as shown in Figure 1.

Figure 1 – Project Location Map

II. DRAINAGE BASINS

A. MAJOR BASINS

The contributing drainage basin has an area of 7.2 square miles and a mean elevation of 6,439 feet. The mean annual precipitation is 54 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 Alder Creek 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 11N46 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 purpose 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 06017C0875E 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) was conducted to compare the peak flow estimates from StreamStats and downstream gage station data.

Precipitation values were obtained from NOAA Atlas 14. HEC-HMS models were simulated for the 6-hour storm event based on the watershed drainage area and lag time. Refer to Appendix D 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 91% Hydrologic Soil Group (HSG) B and 9% HSG D. The CN was estimated for the watershed for both pre- and post-fire conditions. The pre-fire CN was estimated to be 67 based on review of the watershed cover and HSG. Review of the Burned Area Emergency Response (BAER) burn severity map shown below suggests a low-to-moderate burn severity.

Therefore, the estimated CN was 75.

Basin properties and parameters for the HEC-HMS model are summarized in Table 2.

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)

Alder Creek Bridge

7.2 6,439 23.1 54 75 29,200 89

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 1,820 cubic feet per second (cfs). The regression equation estimates have a standard error of prediction of 58.0 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 the project limits. The nearest active station is Alder Creek ID 11440000 which is downstream and has a basin area of 22.0 square miles. The highest stream flow recorded was 5,500 cfs on December 23, 1955. As a means of comparison, this gaged data was prorated to the contributing area to the subject bridge, resulting in an area-prorated 100-year discharge of 2,330 cfs. Gage data is documented in Appendix C.

Comparison of these methodologies validated the use of HEC-HMS 100-year value of 2,145 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 Prorated USGS Gage HEC-HMS

2-year 193 140 348

50-year 1,390 1,660 1,676

100-year 1,820 2,330 2,145

200-year 2,300 3,180 2,694

Figure 3 – BAER Map

B. HYDRAULICS

Flow in Alder 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, it is proposed that the existing stacked abutments be removed, and the abutment slopes be fortified with riprap protection. Fill materials will be removed to natural bedrock. Refer to the bridge plans for the proposed grading and bridge geometry. See the bank protection section in this report for size of riprap.

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. Initial model runs showed overtopping of the overbanks in the downstream portion of the reach, thus CFL survey data was supplemented with USGS LiDAR data where needed.

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 F for computations. A Manning’s ‘n’ value of 0.055 was computed for the natural channel and a value of 0.090 for the overbanks. Jarrett’s Equation was used as a check and found to average 0.072. Since the project is post-burn, the computed value of 0.055 was selected.

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

A significant drop in profile (~6 ft) occurs approximately 250 ft upstream of the bridge location resulting in a hydraulic jump. Cross-sections are defined at the top and bottom of this drop location. It is not anticipated that additional cross-section resolution at this location would result in significant differences to the results at the bridge with respect to the bridge improvements, thus no further analysis was performed.

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.

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 in the existing condition model, however due to proposed grading, the IFA was not needed in the proposed condition as a result of the minimal variation in flow widths through the proposed bridge.

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 520. The controlling point for upstream Section 520 is the southeast corner of the proposed bridge with a low chord elevation of the bridge of 5,577.90. The bridge overtopping elevation at the upstream side is 5,581.78.

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 520 D/S XS Station 485

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

50-year 1,676 5,572.17 5.73 5,570.71 7.19

100-year 2,145 5,572.97 4.93 5,571.14 6.76

100-year (30% Debris Blockage) 2,145 5,573.23 4.67 5,571.22 6.68

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

C. SCOUR AND BANK PROTECTION

As shown in the HEC-RAS model, velocities in Alder Creek at the bridge are up to 12.7 feet per second (fps) in the 100-year event. Since the proposed bridge will be placed on drilled shafts extending to rock, no scour analysis was required. Bedrock was estimated to be 16-17’ below the right bank, which is estimated to be at approximately 5,559’.

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 method was used for the abutment scour estimate which includes the contraction scour estimate, thus scour elevations are set to the thalweg minus the abutment scour. Refer to Appendix I for the scour calculations which were performed using the FHWA hydraulic toolbox software.

Estimated 100-year 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

100-year 2,145 5565.7

1.7 4.3 5,560.5

200-year (check) 2,694 1.9 5.6 5,559.1

Due to the potential for high velocities, bank protection will be provided as a resiliency measure to mitigate possible damage to the roadway embankment. The bank protection will extend upstream, under the bridge and downstream. Riprap will be installed from the channel bottom to the existing bridge abutment at a slope of 2:1. Refer to the bridge plan in Appendix A.

Riprap sizing was determined using HEC-23. The design conditions are as follows.

Design Storm 100-year Design Discharge 2,145 cfs Channel Slope 0.0268 ft/ft Channel Bottom Width 38 ft Channel Sideslope 2:1 Riprap Type Crushed Rock

The results indicate the median size, D50, for channel bottom and side slopes is 18 inches, Method B Class 5. This riprap will be placed to a minimum depth of 48 inches.

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

Alder Creek Bridge Location

1/3/23, 4:21 PM StreamStats https://streamstats.usgs.gov/ss/ 1/2

Alder Creek Bridge StreamStats Report

Collapse All

Basin Characteristics

Parameter Code Parameter Description Value Unit

BSLDEM30M Mean basin slope computed from 30 m DEM 23.1 percent

DRNAREA Area that drains to a point on a stream 7.2 square miles

ELEV Mean Basin Elevation 6439 feet

PRECIP Mean Annual Precipitation 54 inches

Peak-Flow Statistics

Peak-Flow Statistics Parameters [2012 5113 Region 3 Sierra Nevada]

Parameter Code Parameter Name Value Units Min Limit Max Limit

DRNAREA Drainage Area 7.2 square miles 0.07 2000

ELEV Mean Basin Elevation 6439 feet 90 11000

PRECIP Mean Annual Precipitation 54 inches 15 100

Peak-Flow Statistics Flow Report [2012 5113 Region 3 Sierra Nevada]

PIl: Prediction Interval-Lower, PIu: Prediction Interval-Upper, ASEp: Average Standard Error of Prediction, SE: Standard Error (other -- see report)

Statistic Value Unit PIl PIu ASEp

50-percent AEP flood 193 ft^3/s 65.1 572 74.4

20-percent AEP flood 428 ft^3/s 185 992 54.4

10-percent AEP flood 661 ft^3/s 298 1470 51.5

4-percent AEP flood 1030 ft^3/s 464 2290 52.3

2-percent AEP flood 1390 ft^3/s 603 3200 54.6

Region ID: CA Workspace ID: CA20230103231811009000 Clicked Point (Latitude, Longitude): 38.68871, -120.30323 Time: 2023-01-03 16:18:35 -0700

1/3/23, 4:21 PM StreamStats https://streamstats.usgs.gov/ss/ 2/2

Statistic Value Unit PIl PIu ASEp

1-percent AEP flood 1820 ft^3/s 757 4370 58

0.5-percent AEP flood 2300 ft^3/s 912 5800 61.5

0.2-percent AEP flood 3060 ft^3/s 1120 8330 67.3

Peak-Flow Statistics Citations

Gotvald, A.J., Barth, N.A., Veilleux, A.G., and Parrett, Charles,2012, Methods for determining magnitude and frequency of floods in California, based on data through water year 2006: U.S. Geological Survey Scientific Investigations Report 2012–5113, 38 p., 1 pl.

(http://pubs.usgs.gov/sir/2012/5113/)

USGS Data Disclaimer: Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.

USGS Software Disclaimer: This software has been approved for release by the U.S. Geological Survey (USGS). Although the software has been subjected to rigorous review, the USGS reserves the right to update the software as needed pursuant to further analysis and review. No warranty, expressed or implied, is made by the USGS or the U.S. Government as to the functionality of the software and related material nor shall the fact of release constitute any such warranty. Furthermore, the software is released on condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from its authorized or unauthorized use.

USGS Product Names Disclaimer: Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Application Version: 4.11.1

StreamStats Services Version: 1.2.22

NSS Services Version: 2.2.1 http://pubs.usgs.gov/sir/2012/5113/

Appendix C

USGS StreamStats Report

Alder Creek Gage # 11440000

12/16/22, 12:58 PM StreamStats https://streamstats.usgs.gov/ss/ 1/2

StreamStats Data-Collection Station Report

Filter By Statistic Group: Filter By Citation:

Filter By Statistic Group: Filter By Citation: Show Only Preferred

Number (https://nwis.waterdata.usgs.gov/nwis/inventory/?site_no=11440000)

Station Name ALDER C NR WHITEHALL TOTAL FLOW CA

Station Type Gaging Station, continuous record

Latitude 38.75518399

Longitude -120.37241838

NWIS Latitude

NWIS Longitude

Is regulated? true

Agency United States Geological Survey

NWIS Discharge Period of Record

09/30/1922 - 09/28/1981

Physical Characteristics

Precipitation Statistics

Characteristic Name Value Units Citation

Mean Annual Precipitation 54.83 inches 53

Basin Dimensional Characteristics

Characteristic Name Value Units Citation

Drainage Area 22 square miles 53

Topographical Characteristics

Characteristic Name Value Units Citation

Streamflow Statistics nt AEP f lood feet per second

1-perce nt AEP f lood

7110 cubic feet per second

59 39.24 0.0270179994 53

0.5-perc ent AEP flood

9720 cubic feet per second

59 45.67 0.0357359983 53

Citations

Select Select

1 Checked 1 Checked https://waterdata.usgs.gov/monitoring-location/11440000 https://nwis.waterdata.usgs.gov/nwis/inventory/?site_no=11440000

12/16/22, 12:58 PM StreamStats https://streamstats.usgs.gov/ss/ 2/2

ID Citation

53 Gotvald, A.J., Barth, N.A., Veilleux, A.G., and Parrett, Charles, 2012, Methods for determining magnitude and frequency of floods in California, based on data through water year 2006: U.S. Geological Survey Scientific Investigations Report 2012–5113, 38 p., 1 pl. (http://pubs.usgs.gov/sir/2012/5113/)

29 Parrett, C., Veilleux, A., Stedinger, J.R., Barth, N.A., Knifong, D.L., and Ferris, J.C., 2011, Regional skew for California, and flood frequency for selected sites in the Sacramento–San Joaquin River Basin, based on data through water year 2006: U.S. Geological Survey Scientific Investigations Report 2010–5260, 94 p. (http://pubs.usgs.gov/sir/2010/5260/)

52 Granato G.E., Ries, K.G., III, and Steeves, P.A., 2017, Compilation of streamflow statistics calculated from daily mean streamflow data collected during water years 1901–2015 for selected U.S. Geological Survey streamgages: U.S.

Geological Survey Open-File Report 2017-1108, 17 p. (https://pubs.er.usgs.gov/publication/ofr20171108)

86 Wolock, D.M., 2003, Flow characteristics at U.S. Geological Survey streamgages in the conterminous United States: U.S.

http://pubs.usgs.gov/sir/2012/5113/ http://pubs.usgs.gov/sir/2010/5260/ https://pubs.er.usgs.gov/publication/ofr20171108 http://water.usgs.gov/GIS/metadata/usgswrd/XML/qsitesdd.xml

Appendix D

NOAA Atlas 14 Precipitation Data

12/20/22, 1:55 PM Precipitation Frequency Data Server https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=38.6782&lon=-120.2692&data=depth&units=english&series=pds 1/4

NOAA Atlas 14, Volume 6, Version 2 Location name: Kyburz, California, USA* Latitude: 38.6782°, Longitude: -120.2692°

Elevation: 6073.86 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 0.176 (0.152‑0.207)

0.220 (0.189‑0.259)

0.281 (0.241‑0.332)

0.335 (0.284‑0.399)

0.414 (0.336‑0.514)

0.479 (0.379‑0.611)

0.551 (0.423‑0.724)

0.630 (0.468‑0.857)

0.750 (0.529‑1.07)

0.853 (0.578‑1.27)

10-min 0.253 (0.217‑0.297)

0.315 (0.271‑0.371)

0.403 (0.345‑0.476)

0.480 (0.407‑0.572)

0.593 (0.482‑0.737)

0.687 (0.544‑0.876)

0.789 (0.606‑1.04)

0.903 (0.670‑1.23)

1.07 (0.758‑1.54)

1.22 (0.828‑1.83)

15-min 0.305 (0.263‑0.359)

0.381 (0.328‑0.449)

0.488 (0.418‑0.576)

0.581 (0.492‑0.692)

0.717 (0.583‑0.891)

0.831 (0.658‑1.06)

0.954 (0.733‑1.25)

1.09 (0.811‑1.49)

1.30 (0.917‑1.86)

1.48 (1.00‑2.21)

30-min 0.399 (0.343‑0.469)

0.498 (0.428‑0.586)

0.638 (0.546‑0.752)

0.759 (0.643‑0.905)

0.937 (0.762‑1.17)

1.09 (0.859‑1.39)

1.25 (0.958‑1.64)

1.43 (1.06‑1.94)

1.70 (1.20‑2.43)

1.93 (1.31‑2.89)

60-min 0.544 (0.468‑0.638)

0.679 (0.583‑0.799)

0.869 (0.744‑1.02)

1.03 (0.876‑1.23)

1.28 (1.04‑1.59)

1.48 (1.17‑1.89)

1.70 (1.31‑2.23)

1.95 (1.44‑2.65)

2.31 (1.63‑3.31)

2.63 (1.78‑3.93)

2-hr 0.778 (0.669‑0.913)

0.945 (0.812‑1.11)

1.18 (1.01‑1.39)

1.39 (1.18‑1.65)

1.69 (1.37‑2.10)

1.94 (1.54‑2.48)

2.22 (1.70‑2.91)

2.52 (1.87‑3.43)

2.97 (2.09‑4.25)

3.35 (2.27‑5.00)

3-hr 0.978 (0.842‑1.15)

1.18 (1.01‑1.39)

1.46 (1.25‑1.72)

1.70 (1.44‑2.03)

2.06 (1.68‑2.56)

2.36 (1.87‑3.01)

2.68 (2.06‑3.52)

3.03 (2.25‑4.13)

3.55 (2.51‑5.08)

3.99 (2.70‑5.96)

6-hr 1.49 (1.28‑1.74)

1.77 (1.52‑2.09)

2.17 (1.86‑2.57)

2.52 (2.13‑3.00)

3.02 (2.45‑3.75)

3.43 (2.72‑4.38)

3.87 (2.98‑5.09)

4.36 (3.24‑5.93)

5.07 (3.58‑7.25)

5.66 (3.83‑8.45)

12-hr 2.24 (1.92‑2.63)

2.71 (2.32‑3.18)

3.34 (2.86‑3.94)

3.88 (3.29‑4.63)

4.64 (3.77‑5.77)

5.25 (4.16‑6.70)

5.89 (4.53‑7.75)

6.58 (4.89‑8.95)

7.56 (5.33‑10.8)

8.35 (5.65‑12.5)

24-hr 3.32 (2.92‑3.86)

4.13 (3.62‑4.80)

5.20 (4.55‑6.06)

6.09 (5.29‑7.16)

7.32 (6.16‑8.89)

8.29 (6.83‑10.3)

9.30 (7.49‑11.8)

10.4 (8.12‑13.5)

11.8 (8.91‑16.0)

13.0 (9.48‑18.2)

2-day 4.52 (3.97‑5.25)

5.72 (5.01‑6.65)

7.33 (6.42‑8.55)

8.70 (7.55‑10.2)

10.6 (8.93‑12.9)

12.2 (10.0‑15.1)

13.8 (11.1‑17.5)

15.5 (12.1‑20.2)

17.9 (13.5‑24.3)

19.9 (14.5‑27.9)

3-day 5.34 (4.69‑6.20)

6.81 (5.97‑7.92)

8.83 (7.72‑10.3)

10.5 (9.15‑12.4)

13.0 (10.9‑15.8)

15.0 (12.3‑18.5)

17.1 (13.7‑21.6)

19.3 (15.1‑25.2)

22.6 (17.0‑30.6)

25.2 (18.4‑35.3)

4-day 5.98 (5.26‑6.95)

7.67 (6.73‑8.93)

9.98 (8.73‑11.6)

11.9 (10.4‑14.0)

14.7 (12.4‑17.9)

17.0 (14.0‑21.0)

19.4 (15.6‑24.5)

21.9 (17.2‑28.5)

25.6 (19.3‑34.7)

28.6 (20.8‑40.0)

7-day 7.46 (6.55‑8.66)

9.57 (8.39‑11.1)

12.4 (10.8‑14.5)

14.8 (12.8‑17.4)

18.1 (15.2‑21.9)

20.7 (17.1‑25.6)

23.4 (18.9‑29.7)

26.4 (20.6‑34.3)

30.4 (22.9‑41.3)

33.8 (24.6‑47.3)

10-day 8.61 (7.56‑10.0)

11.0 (9.69‑12.9)

14.3 (12.5‑16.6)

16.9 (14.7‑19.9)

20.6 (17.3‑25.0)

23.5 (19.4‑29.1)

26.5 (21.3‑33.6)

29.6 (23.2‑38.6)

34.0 (25.6‑46.1)

37.5 (27.3‑52.5)

20-day 11.8 (10.3‑13.7)

15.2 (13.3‑17.6)

19.5 (17.1‑22.8)

23.0 (20.0‑27.1)

27.8 (23.4‑33.7)

31.4 (25.9‑38.9)

35.1 (28.3‑44.5)

38.9 (30.5‑50.7)

44.1 (33.2‑59.8)

48.2 (35.1‑67.6)

30-day 14.5 (12.7‑16.8)

18.7 (16.4‑21.7)

24.0 (21.0‑28.0)

28.2 (24.5‑33.2)

33.8 (28.4‑41.1)

38.1 (31.4‑47.1)

42.3 (34.1‑53.7)

46.7 (36.6‑60.8)

52.5 (39.5‑71.2)

57.1 (41.6‑80.0)

45-day 18.1 (15.9‑21.0)

23.3 (20.4‑27.1)

29.8 (26.1‑34.8)

34.9 (30.3‑41.1)

41.6 (35.0‑50.5)

46.6 (38.4‑57.7)

51.5 (41.5‑65.3)

56.5 (44.3‑73.6)

63.1 (47.5‑85.5)

68.1 (49.6‑95.5)

60-day 21.4 (18.8‑24.8)

27.5 (24.1‑31.9)

35.0 (30.6‑40.8)

40.9 (35.5‑48.1)

48.5 (40.8‑58.8)

54.1 (44.5‑66.9)

59.5 (47.9‑75.5)

65.0 (50.9‑84.7)

72.2 (54.4‑97.9)

77.6 (56.5‑109)

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=38.6782&lon=-120.2692&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=38.6782&lon=-120.2692&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=38.6782&lon=-120.2692&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 E

HEC-HMS Model Output

DATE 12/20/2022

PROJECT CFL - Alder Creek Bridge

SUBJECT Hydrology Calculations

BY JDS

REFERENCE USDA NRCS Part 630 Hydrology - National Engineering Handbook -

Chapter 15 Time of Concentration

Method 630.1502 - Watershed Lag Method

Lag Time Input l 29200 ft

Y 23.1 % cn' (CN) 75

S 3.33 in

Lag Time, L 89.2 min

HMS Output - 6hr storm

Q - 50yr 1676 cfs

Q - 100yr 2145 cfs

Q - 200yr 2694 cfs

HMS Output - 3hr storm

Q - 50yr 1081 cfs

Q - 100yr 1440 cfs

Q - 200yr 1866 cfs

Notes

6hr storm used as a conservative result

Appendix F

Manning’s n Calculation

Project: Alder Creek 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 appreciable 0.020 n4 = Table 3 large 0.040 m = Table 3 minor 1.0 n = 0.090

Channel nb = Table 1 0.5 mm 0.022 n1 = Table 2 occasional 0.008 n2 = Table 2 gradual 0.005 n3 = Table 2 minor 0.015 n4 = Table 2 small 0.005 m = Table 2 minor 1.0 n = 0.055

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 0.020 n4 = Table 3 large 0.040 m = Table 3 minor 1.0 n = 0.090

JPF

12/20/2022

WXYA2205

JDS

Appendix G

HEC-RAS Output

0 200 400 600 800 1000 1200

2023-01-04_Alder_Creek Plan: Existing 1/4/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

2023-01-04_Alder_Creek Plan: Existing_Mixed 1/4/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

2023-04-23_Alder_Creek Plan: 1) prop_sub 4/24/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

2023-04-23_Alder_Creek Plan: 1) prop_30pct_sub 4/24/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

2023-04-23_Alder_Creek Plan: 1) prop_30pct_mix 4/24/2023

Main Channel Distance (ft)

E le v a ti o n ft

Legend

WS 200yr

WS 100yr

WS 50yr

WS 2yr

Ground

LOB

ROB

2023-04-23_Alder_Creek Plan: Proposed_Mixed 4/24/2023

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: Alder Creek Reach: Bridge

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)

Bridge 1104 2yr Ex_sub 348.00 5586.47 5590.42 5590.76 0.012838 4.66 74.84 32.55 0.53

Bridge 1104 2yr Ex_mix 348.00 5586.47 5590.42 5589.45 5590.76 0.012838 4.66 74.84 32.55 0.53

Bridge 1104 2yr prop_sub 348.00 5586.47 5590.42 5590.75 0.012896 4.67 74.73 32.53 0.53

Bridge 1104 2yr prop_mix 348.00 5586.47 5590.42 5589.45 5590.75 0.012896 4.67 74.73 32.53 0.53

Bridge 1104 2yr prop_30pct_sub 348.00 5586.47 5590.42 5590.76 0.012838 4.66 74.84 32.55 0.53

Bridge 1104 2yr prop_30pct_mix 348.00 5586.47 5590.42 5589.45 5590.76 0.012838 4.66 74.84 32.55 0.53

Bridge 1104 50yr Ex_sub 1676.00 5586.47 5593.23 5594.65 0.021531 9.75 185.03 44.33 0.76

Bridge 1104 50yr Ex_mix 1676.00 5586.47 5593.23 5592.50 5594.65 0.021531 9.75 185.03 44.33 0.76

Bridge 1104 50yr prop_sub 1676.00 5586.47 5593.23 5594.65 0.021531 9.75 185.03 44.33 0.76

Bridge 1104 50yr prop_mix 1676.00 5586.47 5593.23 5592.50 5594.65 0.021531 9.75 185.03 44.33 0.76

Bridge 1104 50yr prop_30pct_sub 1676.00 5586.47 5593.23 5594.65 0.021531 9.75 185.03 44.33 0.76

Bridge 1104 50yr prop_30pct_mix 1676.00 5586.47 5593.23 5592.50 5594.65 0.021531 9.75 185.03 44.33 0.76

Bridge 1104 100yr Ex_sub 2145.00 5586.47 5593.84 5593.26 5595.64 0.023629 11.02 212.83 46.40 0.81

Bridge 1104 100yr Ex_mix 2145.00 5586.47 5593.84 5593.26 5595.64 0.023629 11.02 212.83 46.40 0.81

Bridge 1104 100yr prop_sub 2145.00 5586.47 5593.84 5593.26 5595.64 0.023629 11.02 212.83 46.40 0.81

Bridge 1104 100yr prop_mix 2145.00 5586.47 5593.84 5593.26 5595.64 0.023629 11.02 212.83 46.40 0.81

Bridge 1104 100yr prop_30pct_sub 2145.00 5586.47 5593.84 5593.26 5595.64 0.023629 11.02 212.83 46.40 0.81

Bridge 1104 100yr prop_30pct_mix 2145.00 5586.47 5593.84 5593.26 5595.64 0.023629 11.02 212.83 46.40 0.81

Bridge 1104 200yr Ex_sub 2694.00 5586.47 5594.48 5594.08 5596.71 0.025504 12.29 243.31 48.38 0.86

Bridge 1104 200yr Ex_mix 2694.00 5586.47 5594.48 5594.08 5596.71 0.025504 12.29 243.31 48.38 0.86

Bridge 1104 200yr prop_sub 2694.00 5586.47 5594.48 5594.08 5596.71 0.025504 12.29 243.31 48.38 0.86

Bridge 1104 200yr prop_mix 2694.00 5586.47 5594.48 5594.08 5596.71 0.025504 12.29 243.31 48.38 0.86

Bridge 1104 200yr prop_30pct_sub 2694.00 5586.47 5594.48 5594.08 5596.71 0.025504 12.29 243.31 48.38 0.86

Bridge 1104 200yr prop_30pct_mix 2694.00 5586.47 5594.48 5594.08 5596.71 0.025504 12.29 243.31 48.38 0.86

Bridge 993 2yr Ex_sub 348.00 5584.91 5587.60 5587.50 5588.18 0.054440 6.09 57.13 41.19 0.91

Bridge 993 2yr Ex_mix 348.00 5584.91 5587.60 5587.50 5588.18 0.054440 6.09 57.13 41.19 0.91

Bridge 993 2yr prop_sub 348.00 5584.91 5587.61 5587.50 5588.18 0.053775 6.06 57.39 41.25 0.91

Bridge 993 2yr prop_mix 348.00 5584.91 5587.61 5587.50 5588.18 0.053775 6.06 57.39 41.25 0.91

Bridge 993 2yr prop_30pct_sub 348.00 5584.91 5587.60 5587.50 5588.18 0.054440 6.09 57.13 41.19 0.91

Bridge 993 2yr prop_30pct_mix 348.00 5584.91 5587.60 5587.50 5588.18 0.054440 6.09 57.13 41.19 0.91

Bridge 993 50yr Ex_sub 1676.00 5584.91 5590.25 5589.87 5591.58 0.036878 9.28 183.49 52.84 0.84

Bridge 993 50yr Ex_mix 1676.00 5584.91 5590.25 5589.87 5591.58 0.036878 9.28 183.49 52.84 0.84

Bridge 993 50yr prop_sub 1676.00 5584.91 5590.25 5589.87 5591.58 0.036878 9.28 183.49 52.84 0.84

Bridge 993 50yr prop_mix 1676.00 5584.91 5590.25 5589.87 5591.58 0.036878 9.28 183.49 52.84 0.84

Bridge 993 50yr prop_30pct_sub 1676.00 5584.91 5590.25 5589.87 5591.58 0.036878 9.28 183.49 52.84 0.84

Bridge 993 50yr prop_30pct_mix 1676.00 5584.91 5590.25 5589.87 5591.58 0.036878 9.28 183.49 52.84 0.84

Bridge 993 100yr Ex_sub 2145.00 5584.91 5590.94 5590.47 5592.47 0.033906 9.97 221.19 55.28 0.83

Bridge 993 100yr Ex_mix 2145.00 5584.91 5590.94 5590.47 5592.47 0.033906 9.97 221.19 55.28 0.83

Bridge 993 100yr prop_sub 2145.00 5584.91 5590.94 5590.47 5592.47 0.033906 9.97 221.19 55.28 0.83

Bridge 993 100yr prop_mix 2145.00 5584.91 5590.94 5590.47 5592.47 0.033906 9.97 221.19 55.28 0.83

Bridge 993 100yr prop_30pct_sub 2145.00 5584.91 5590.94 5590.47 5592.47 0.033906 9.97 221.19 55.28 0.83

Bridge 993 100yr prop_30pct_mix 2145.00 5584.91 5590.94 5590.47 5592.47 0.033906 9.97 221.19 55.28 0.83

Bridge 993 200yr Ex_sub 2694.00 5584.91 5591.63 5591.15 5593.40 0.032762 10.78 259.88 57.60 0.84

Bridge 993 200yr Ex_mix 2694.00 5584.91 5591.63 5591.15 5593.40 0.032762 10.78 259.88 57.60 0.84

HEC-RAS River: Alder Creek Reach: Bridge (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)

Bridge 993 200yr prop_sub 2694.00 5584.91 5591.63 5591.15 5593.40 0.032762 10.78 259.88 57.60 0.84

Bridge 993 200yr prop_mix 2694.00 5584.91 5591.63 5591.15 5593.40 0.032762 10.78 259.88 57.60 0.84

Bridge 993 200yr prop_30pct_sub 2694.00 5584.91 5591.63 5591.15 5593.40 0.032762 10.78 259.88 57.60 0.84

Bridge 993 200yr prop_30pct_mix 2694.00 5584.91 5591.63 5591.15 5593.40 0.032762 10.78 259.88 57.60 0.84

Bridge 894 2yr Ex_sub 348.00 5581.37 5584.22 5584.67 0.024468 5.42 64.27 36.12 0.70

Bridge 894 2yr Ex_mix 348.00 5581.37 5584.22 5584.67 0.024468 5.42 64.27 36.12 0.70

Bridge 894 2yr prop_sub 348.00 5581.37 5584.21 5584.67 0.024670 5.44 64.10 36.06 0.70

Bridge 894 2yr prop_mix 348.00 5581.37 5584.21 5584.67 0.024670 5.44 64.10 36.06 0.70

Bridge 894 2yr prop_30pct_sub 348.00 5581.37 5584.22 5584.67 0.024468 5.42 64.27 36.12 0.70

Bridge 894 2yr prop_30pct_mix 348.00 5581.37 5584.22 5584.67 0.024468 5.42 64.27 36.12 0.70

Bridge 894 50yr Ex_sub 1676.00 5581.37 5586.74 5586.52 5588.15 0.032344 9.88 188.02 56.94 0.86

Bridge 894 50yr Ex_mix 1676.00 5581.37 5586.74 5586.52 5588.15 0.032344 9.88 188.02 56.94 0.86

Bridge 894 50yr prop_sub 1676.00 5581.37 5586.74 5586.52 5588.15 0.032344 9.88 188.02 56.94 0.86

Bridge 894 50yr prop_mix 1676.00 5581.37 5586.74 5586.52 5588.15 0.032344 9.88 188.02 56.94 0.86

Bridge 894 50yr prop_30pct_sub 1676.00 5581.37 5586.74 5586.52 5588.15 0.032344 9.88 188.02 56.94 0.86

Bridge 894 50yr prop_30pct_mix 1676.00 5581.37 5586.74 5586.52 5588.15 0.032344 9.88 188.02 56.94 0.86

Bridge 894 100yr Ex_sub 2145.00 5581.37 5587.24 5587.16 5588.98 0.036017 11.03 217.38 59.26 0.92

Bridge 894 100yr Ex_mix 2145.00 5581.37 5587.24 5587.16 5588.98 0.036017 11.03 217.38 59.26 0.92

Bridge 894 100yr prop_sub 2145.00 5581.37 5587.24 5587.16 5588.98 0.036017 11.03 217.38 59.26 0.92

Bridge 894 100yr prop_mix 2145.00 5581.37 5587.24 5587.16 5588.98 0.036017 11.03 217.38 59.26 0.92

Bridge 894 100yr prop_30pct_sub 2145.00 5581.37 5587.24 5587.16 5588.98 0.036017 11.03 217.38 59.26 0.92

Bridge 894 100yr prop_30pct_mix 2145.00 5581.37 5587.24 5587.16 5588.98 0.036017 11.03 217.38 59.26 0.92

Bridge 894 200yr Ex_sub 2694.00 5581.37 5587.80 5587.80 5589.86 0.038589 12.05 251.38 61.78 0.95

Bridge 894 200yr Ex_mix 2694.00 5581.37 5587.80 5587.80 5589.86 0.038589 12.05 251.38 61.78 0.95

Bridge 894 200yr prop_sub 2694.00 5581.37 5587.80 5587.80 5589.86 0.038589 12.05 251.38 61.78 0.95

Bridge 894 200yr prop_mix 2694.00 5581.37 5587.80 5587.80 5589.86 0.038589 12.05 251.38 61.78 0.95

Bridge 894 200yr prop_30pct_sub 2694.00 5581.37 5587.80 5587.80 5589.86 0.038589 12.05 251.38 61.78 0.95

Bridge 894 200yr prop_30pct_mix 2694.00 5581.37 5587.80 5587.80 5589.86 0.038589 12.05 251.38 61.78 0.95

Bridge 826 2yr Ex_sub 348.00 5579.92 5582.47 5582.21 5582.83 0.029049 4.82 72.24 54.93 0.74

Bridge 826 2yr Ex_mix 348.00 5579.92 5582.47 5582.21 5582.83 0.029049 4.82 72.24 54.93 0.74

Bridge 826 2yr prop_sub 348.00 5579.92 5582.47 5582.20 5582.83 0.028449 4.78 72.75 55.03 0.73

Bridge 826 2yr prop_mix 348.00 5579.92 5582.47 5582.20 5582.83 0.028449 4.78 72.75 55.03 0.73

Bridge 826 2yr prop_30pct_sub 348.00 5579.92 5582.47 5582.21 5582.83 0.029049 4.82 72.24 54.93 0.74

Bridge 826 2yr prop_30pct_mix 348.00 5579.92 5582.47 5582.21 5582.83 0.029049 4.82 72.24 54.93 0.74

Bridge 826 50yr Ex_sub 1676.00 5579.92 5584.22 5584.19 5585.60 0.043255 9.46 177.88 65.31 0.99

Bridge 826 50yr Ex_mix 1676.00 5579.92 5584.22 5584.19 5585.60 0.043255 9.46 177.88 65.31 0.99

Bridge 826 50yr prop_sub 1676.00 5579.92 5584.22 5584.19 5585.60 0.043255 9.46 177.88 65.31 0.99

Bridge 826 50yr prop_mix 1676.00 5579.92 5584.22 5584.19 5585.60 0.043255 9.46 177.88 65.31 0.99

Bridge 826 50yr prop_30pct_sub 1676.00 5579.92 5584.22 5584.19 5585.60 0.043255 9.46 177.88 65.31 0.99

Bridge 826 50yr prop_30pct_mix 1676.00 5579.92 5584.22 5584.19 5585.60 0.043255 9.46 177.88 65.31 0.99

Bridge 826 100yr Ex_sub 2145.00 5579.92 5584.74 5584.74 5586.34 0.040347 10.16 213.51 68.91 0.98

Bridge 826 100yr Ex_mix 2145.00 5579.92 5584.74 5584.74 5586.34 0.040347 10.16 213.51 68.91 0.98

Bridge 826 100yr prop_sub 2145.00 5579.92 5584.74 5584.74 5586.34 0.040347 10.16 213.51 68.91 0.98

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)

Bridge 826 100yr prop_mix 2145.00 5579.92 5584.74 5584.74 5586.34 0.040347 10.16 213.51 68.91 0.98

Bridge 826 100yr prop_30pct_sub 2145.00 5579.92 5584.74 5584.74 5586.34 0.040347 10.16 213.51 68.91 0.98

Bridge 826 100yr prop_30pct_mix 2145.00 5579.92 5584.74 5584.74 5586.34 0.040347 10.16 213.51 68.91 0.98

Bridge 826 200yr Ex_sub 2694.00 5579.92 5585.28 5585.28 5587.12 0.038751 10.92 251.09 71.28 0.97

Bridge 826 200yr Ex_mix 2694.00 5579.92 5585.23 5585.28 5587.12 0.040365 11.06 247.75 71.07 0.99

Bridge 826 200yr prop_sub 2694.00 5579.92 5585.28 5585.28 5587.12 0.038751 10.92 251.09 71.28 0.97

Bridge 826 200yr prop_mix 2694.00 5579.92 5585.23 5585.28 5587.12 0.040365 11.06 247.75 71.07 0.99

Bridge 826 200yr prop_30pct_sub 2694.00 5579.92 5585.28 5585.28 5587.12 0.038751 10.92 251.09 71.28 0.97

Bridge 826 200yr prop_30pct_mix 2694.00 5579.92 5585.23 5585.28 5587.12 0.040365 11.06 247.75 71.07 0.99

Bridge 733 2yr Ex_sub 348.00 5576.16 5578.03 5578.03 5578.46 0.086491 5.24 66.39 78.27 1.00

Bridge 733 2yr Ex_mix 348.00 5576.16 5578.03 5578.03 5578.46 0.086491 5.24 66.39 78.27 1.00

Bridge 733 2yr prop_sub 348.00 5576.16 5578.02 5578.02 5578.46 0.090467 5.32 65.44 78.07 1.02

Bridge 733 2yr prop_mix 348.00 5576.16 5578.02 5578.02 5578.46 0.090467 5.32 65.44 78.07 1.02

Bridge 733 2yr prop_30pct_sub 348.00 5576.16 5578.03 5578.03 5578.46 0.086491 5.24 66.39 78.27 1.00

Bridge 733 2yr prop_30pct_mix 348.00 5576.16 5578.03 5578.03 5578.46 0.086491 5.24 66.39 78.27 1.00

Bridge 733 50yr Ex_sub 1676.00 5576.16 5579.57 5579.57 5580.65 0.063699 8.36 200.58 92.65 1.00

Bridge 733 50yr Ex_mix 1676.00 5576.16 5579.57 5579.57 5580.65 0.063699 8.36 200.58 92.65 1.00

Bridge 733 50yr prop_sub 1676.00 5576.16 5579.57 5579.57 5580.65 0.063699 8.36 200.58 92.65 1.00

Bridge 733 50yr prop_mix 1676.00 5576.16 5579.57 5579.57 5580.65 0.063699 8.36 200.58 92.65 1.00

Bridge 733 50yr prop_30pct_sub 1676.00 5576.16 5579.57 5579.57 5580.65 0.063699 8.36 200.58 92.65 1.00

Bridge 733 50yr prop_30pct_mix 1676.00 5576.16 5579.57 5579.57 5580.65 0.063699 8.36 200.58 92.65 1.00

Bridge 733 100yr Ex_sub 2145.00 5576.16 5579.96 5579.96 5581.23 0.062049 9.05 236.97 94.39 1.01

Bridge 733 100yr Ex_mix 2145.00 5576.16 5579.80 5579.96 5581.25 0.076101 9.67 221.91 93.68 1.11

Bridge 733 100yr prop_sub 2145.00 5576.16 5579.96 5579.96 5581.23 0.062049 9.05 236.97 94.39 1.01

Bridge 733 100yr prop_mix 2145.00 5576.16 5579.80 5579.96 5581.25 0.076101 9.67 221.91 93.68 1.11

Bridge 733 100yr prop_30pct_sub 2145.00 5576.16 5579.96 5579.96 5581.23 0.062049 9.05 236.97 94.39 1.01

Bridge 733 100yr prop_30pct_mix 2145.00 5576.16 5579.80 5579.96 5581.25 0.076101 9.67 221.91 93.68 1.11

Bridge 733 200yr Ex_sub 2694.00 5576.16 5580.38 5580.38 5581.85 0.060164 9.71 277.38 96.30 1.01

Bridge 733 200yr Ex_mix 2694.00 5576.16 5580.11 5580.38 5581.89 0.081352 10.71 251.54 95.09 1.16

Bridge 733 200yr prop_sub 2694.00 5576.16 5580.38 5580.38 5581.85 0.060164 9.71 277.38 96.30 1.01

Bridge 733 200yr prop_mix 2694.00 5576.16 5580.11 5580.38 5581.89 0.081352 10.71 251.54 95.09 1.16

Bridge 733 200yr prop_30pct_sub 2694.00 5576.16 5580.38 5580.38 5581.85 0.060164 9.71 277.38 96.30 1.01

Bridge 733 200yr prop_30pct_mix 2694.00 5576.16 5580.11 5580.38 5581.89 0.081352 10.71 251.54 95.09 1.16

Bridge 698 2yr Ex_sub 348.00 5569.98 5572.49 5572.27 5573.03 0.026565 5.91 58.86 37.25 0.83

Bridge 698 2yr Ex_mix 348.00 5569.98 5571.66 5572.27 5573.78 0.208511 11.69 29.77 32.07 2.14

Bridge 698 2yr prop_sub 348.00 5569.98 5572.49 5572.27 5573.03 0.026541 5.91 58.88 37.25 0.83

Bridge 698 2yr prop_mix 348.00 5569.98 5571.66 5572.27 5573.78 0.208511 11.69 29.77 32.07 2.14

Bridge 698 2yr prop_30pct_sub 348.00 5569.98 5572.50 5572.27 5573.03 0.025836 5.86 59.41 37.32 0.82

Bridge 698 2yr prop_30pct_mix 348.00 5569.98 5571.66 5572.27 5573.78 0.208511 11.69 29.77 32.07 2.14

Bridge 698 50yr Ex_sub 1676.00 5569.98 5574.86 5574.86 5576.54 0.031302 10.42 160.89 48.12 1.00

Bridge 698 50yr Ex_mix 1676.00 5569.98 5573.65 5574.86 5577.56 0.108208 15.86 105.66 43.15 1.79

Bridge 698 50yr prop_sub 1676.00 5569.98 5574.86 5574.86 5576.54 0.031302 10.42 160.89 48.12 1.00

Bridge 698 50yr prop_mix 1676.00 5569.98 5573.65 5574.86 5577.56 0.108208 15.86 105.66 43.15 1.79

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)

Bridge 698 50yr prop_30pct_sub 1676.00 5569.98 5574.86 5574.86 5576.54 0.031302 10.42 160.89 48.12 1.00

Bridge 698 50yr prop_30pct_mix 1676.00 5569.98 5573.65 5574.86 5577.56 0.108208 15.86 105.66 43.15 1.79

Bridge 698 100yr Ex_sub 2145.00 5569.98 5575.51 5575.51 5577.43 0.029943 11.10 193.27 50.55 1.00

Bridge 698 100yr Ex_mix 2145.00 5569.98 5574.31 5575.51 5578.22 0.085666 15.87 135.18 45.99 1.63

Bridge 698 100yr prop_sub 2145.00 5569.98 5575.51 5575.51 5577.43 0.029943 11.10 193.27 50.55 1.00

Bridge 698 100yr prop_mix 2145.00 5569.98 5574.31 5575.51 5578.22 0.085666 15.87 135.18 45.99 1.63

Bridge 698 100yr prop_30pct_sub 2145.00 5569.98 5575.51 5575.51 5577.43 0.029943 11.10 193.27 50.55 1.00

Bridge 698 100yr prop_30pct_mix 2145.00 5569.98 5574.31 5575.51 5578.22 0.085666 15.87 135.18 45.99 1.63

Bridge 698 200yr Ex_sub 2694.00 5569.98 5576.18 5576.18 5578.36 0.028595 11.85 227.85 54.22 1.00

Bridge 698 200yr Ex_mix 2694.00 5569.98 5574.98 5576.17 5579.03 0.072481 16.13 167.01 48.60 1.53

Bridge 698 200yr prop_sub 2694.00 5569.98 5576.18 5576.18 5578.36 0.028595 11.85 227.85 54.22 1.00

Bridge 698 200yr prop_mix 2694.00 5569.98 5574.98 5576.17 5579.03 0.072481 16.13 167.01 48.60 1.53

Bridge 698 200yr prop_30pct_sub 2694.00 5569.98 5576.18 5576.18 5578.36 0.028595 11.85 227.85 54.22 1.00

Bridge 698 200yr prop_30pct_mix 2694.00 5569.98 5574.98 5576.17 5579.03 0.072481 16.13 167.01 48.60 1.53

Bridge 645 2yr Ex_sub 348.00 5568.42 5570.72 5570.64 5571.42 0.034832 6.72 51.81 33.18 0.95

Bridge 645 2yr Ex_mix 348.00 5568.42 5570.72 5570.65 5571.42 0.034832 6.72 51.81 33.18 0.95

Bridge 645 2yr prop_sub 348.00 5568.42 5570.72 5570.64 5571.42 0.034921 6.72 51.76 33.17 0.95

Bridge 645 2yr prop_mix 348.00 5568.42 5570.72 5570.65 5571.42 0.034921 6.72 51.76 33.17 0.95

Bridge 645 2yr prop_30pct_sub 348.00 5568.42 5570.69 5570.65 5571.42 0.036235 6.81 51.07 32.97 0.97

Bridge 645 2yr prop_30pct_mix 348.00 5568.42 5570.69 5570.65 5571.42 0.036235 6.81 51.07 32.97 0.97

Bridge 645 50yr Ex_sub 1676.00 5568.42 5573.35 5573.29 5574.90 0.027156 10.04 170.19 53.96 0.95

Bridge 645 50yr Ex_mix 1676.00 5568.42 5573.35 5573.29 5574.90 0.027156 10.04 170.19 53.96 0.95

Bridge 645 50yr prop_sub 1676.00 5568.42 5573.35 5573.29 5574.90 0.027181 10.05 170.13 53.95 0.95

Bridge 645 50yr prop_mix 1676.00 5568.42 5573.34 5573.29 5574.90 0.027383 10.07 169.71 53.91 0.95

Bridge 645 50yr prop_30pct_sub 1676.00 5568.42 5573.54 5573.29 5574.92 0.022889 9.51 180.26 54.89 0.88

Bridge 645 50yr prop_30pct_mix 1676.00 5568.42 5573.54 5573.29 5574.92 0.022889 9.51 180.26 54.89 0.88

Bridge 645 100yr Ex_sub 2145.00 5568.42 5574.00 5573.91 5575.75 0.025184 10.69 206.48 57.38 0.94

Bridge 645 100yr Ex_mix 2145.00 5568.42 5574.00 5573.91 5575.75 0.025184 10.69 206.48 57.38 0.94

Bridge 645 100yr prop_sub 2145.00 5568.42 5573.97 5573.91 5575.75 0.025889 10.79 204.52 57.19 0.95

Bridge 645 100yr prop_mix 2145.00 5568.42 5573.92 5573.91 5575.75 0.026961 10.94 201.68 56.92 0.97

Bridge 645 100yr prop_30pct_sub 2145.00 5568.42 5574.35 5573.91 5575.80 0.019225 9.79 226.66 59.17 0.83

Bridge 645 100yr prop_30pct_mix 2145.00 5568.42 5574.35 5573.91 5575.80 0.019225 9.79 226.66 59.17 0.83

Bridge 645 200yr Ex_sub 2694.00 5568.42 5574.74 5574.57 5576.63 0.022844 11.19 250.00 61.07 0.91

Bridge 645 200yr Ex_mix 2694.00 5568.42 5574.74 5574.57 5576.63 0.022844 11.19 250.00 61.07 0.91

Bridge 645 200yr prop_sub 2694.00 5568.42 5574.65 5574.57 5576.63 0.024331 11.43 244.59 60.63 0.94

Bridge 645 200yr prop_mix 2694.00 5568.42 5574.57 5574.57 5576.62 0.025713 11.64 239.95 60.26 0.96

Bridge 645 200yr prop_30pct_sub 2694.00 5568.42 5575.26 5576.74 0.016107 9.95 282.42 64.35 0.78

Bridge 645 200yr prop_30pct_mix 2694.00 5568.42 5575.26 5574.57 5576.74 0.016107 9.95 282.42 64.35 0.78

Bridge 579 2yr Ex_sub 348.00 5565.80 5569.52 5569.90 0.014647 4.98 69.87 36.13 0.63

Bridge 579 2yr Ex_mix 348.00 5565.80 5569.52 5569.90 0.014647 4.98 69.87 36.13 0.63

Bridge 579 2yr prop_sub 348.00 5565.80 5569.52 5569.91 0.014513 4.96 70.15 36.25 0.63

Bridge 579 2yr prop_mix 348.00 5565.80 5569.52 5569.91 0.014513 4.96 70.15 36.25 0.63

Bridge 579 2yr prop_30pct_sub 348.00 5565.80 5569.62 5569.97 0.012959 4.73 73.60 37.55 0.60

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)

Bridge 579 2yr prop_30pct_mix 348.00 5565.80 5569.62 5569.97 0.012959 4.73 73.60 37.55 0.60

Bridge 579 50yr Ex_sub 1676.00 5565.80 5572.57 5573.46 0.013932 7.55 222.07 58.99 0.69

Bridge 579 50yr Ex_mix 1676.00 5565.80 5572.57 5573.46 0.013932 7.55 222.07 58.99 0.69

Bridge 579 50yr prop_sub 1676.00 5565.80 5572.56 5573.45 0.014065 7.57 221.35 58.93 0.69

Bridge 579 50yr prop_mix 1676.00 5565.80 5572.29 5573.32 0.017428 8.15 205.71 57.71 0.76

Bridge 579 50yr prop_30pct_sub 1676.00 5565.80 5573.12 5573.79 0.009275 6.56 255.43 61.54 0.57

Bridge 579 50yr prop_30pct_mix 1676.00 5565.80 5573.12 5573.79 0.009275 6.56 255.43 61.54 0.57

Bridge 579 100yr Ex_sub 2145.00 5565.80 5573.44 5574.38 0.012269 7.80 275.04 62.99 0.66

Bridge 579 100yr Ex_mix 2145.00 5565.80 5573.44 5574.38 0.012269 7.80 275.04 62.99 0.66

Bridge 579 100yr prop_sub 2145.00 5565.80 5573.34 5574.33 0.013137 7.99 268.61 62.52 0.68

Bridge 579 100yr prop_mix 2145.00 5565.80 5573.02 5574.17 0.016409 8.62 248.73 61.04 0.75

Bridge 579 100yr prop_30pct_sub 2145.00 5565.80 5574.07 5574.78 0.008287 6.80 315.42 65.94 0.55

Bridge 579 100yr prop_30pct_mix 2145.00 5565.80 5574.07 5574.78 0.008287 6.80 315.42 65.94 0.55

Bridge 579 200yr Ex_sub 2694.00 5565.80 5574.33 5575.35 0.011079 8.08 333.61 70.57 0.64

Bridge 579 200yr Ex_mix 2694.00 5565.80 5574.33 5575.35 0.011079 8.08 333.61 70.57 0.64

Bridge 579 200yr prop_sub 2694.00 5565.80 5574.15 5575.24 0.012448 8.40 320.81 66.47 0.67

Bridge 579 200yr prop_mix 2694.00 5565.80 5573.79 5572.84 5575.06 0.015502 9.07 297.10 64.58 0.75

Bridge 579 200yr prop_30pct_sub 2694.00 5565.80 5575.07 5575.83 0.007353 7.02 392.12 87.53 0.52

Bridge 579 200yr prop_30pct_mix 2694.00 5565.80 5575.07 5575.83 0.007353 7.02 392.12 87.53 0.52

Bridge 520 2yr Ex_sub 348.00 5565.72 5569.06 5568.08 5569.23 0.007422 3.35 103.86 53.02 0.42

Bridge 520 2yr Ex_mix 348.00 5565.72 5569.06 5568.08 5569.23 0.007422 3.35 103.86 53.02 0.42

Bridge 520 2yr prop_sub 348.00 5565.72 5569.08 5568.07 5569.25 0.007147 3.31 105.13 53.10 0.41

Bridge 520 2yr…