San_Vicente_CA2020(1)_Final_Hydraulics_Report_wAppendices.pdf

San Vicente Bridges Bureau of Land Management

Santa Cruz County, CA

CA BLM 2020(1)

Final Hydraulic Report

Federal Highway Administration Central Federal Lands Highway Division

October 22, 2019

Executive Summary Hydrologic and hydraulic analyses were conducted for the CA BLM 2020(1) San Vicente Bridges Project – Bridge 1. Based on the site constraints and the expectation that the road is not open to public vehicular travel a 5-year flood with freeboard, and a 10-year flood were selected as the design and check floods, respectively. The peak flow values were estimated using USGS regression equations for California. Existing and proposed conditions two-dimensional hydraulic modeling using SRH-2D was conducted to estimate water surface elevations at the project site. Based on the hydraulic results the following proposed bridge geometry was selected:

• Proposed bridge low chord of 1000.3 feet (local datum).

• Proposed bridge waterway opening width of 46 feet.

• Proposed abutments are spread footings embedded on non-erodible bedrock.

i CA2020(1) San Vicente Bridges - Hydraulic Report

Table of Contents

1 Project Background Information

2 Hydraulic Design Criteria

3 Hydrology

3.1 Hydrologic Setting

3.2 FEMA Flood Insurance Study

3.3 Available Hydrologic Data

3.4 Regression Equation Estimates

3.5 Recommended Design Discharges

4 Hydraulic Analysis

4.1 Topographic Information

4.2 Hydraulic Model Development

4.3 Hydraulic Model Results

4.3.1 Existing Conditions

4.3.2 Proposed Conditions

4.4 Scour Considerations

5 Recommendations

6 References ii CA2020(1) San Vicente Bridges - Hydraulic Report

Tables Table 1: PDDM Hydraulic Design Criteria Table 2: Project Hydraulic Design Criteria Table 3: San Vicente Creek at Bridge 1 Basin Properties Table 4: FEMA FIS San Vicente Creek at Mouth Peak Flows Table 5: Available Peak Streamflow Information Table 6: USGS 11161800 Peak Streamflow Table 7: StreamStats Peak Discharge Estimates at Project Location Table 8: Peak Discharge – Weighted Estimates at Project Location using data from USGS 11161800 Table 9: Recommended Design Flows for San Vicente Creek at Bridge 1 Table 10: Model Boundary Condiitons Table 11: Recommended Design Flows for San Vicente Creek at Bridge 1 Table 12: Existing Conditions Hydraulic Results – Bridge Opening at Upstream Bridge Face Table 13: Existing Conditions Hydraulic Results – Floodplain Upstream of Bridge Table 14: Proposed Conditions Hydraulic Results – Bridge Opening at Upstream Bridge Face Table 15: Proposed Conditions Hydraulic Results – Floodplain Upstream of Bridge Table 16: Proposed Conditions Freeboard Table 17: Proposed vs Existing 100-Year Water Surface Elevations

Figures

Figure 1: Project location map Figure 2: San Vicente Creek Bridge 1 Basin Figure 3: FEMA National Flood Hazard Layer – FIRM Excerpt Figure 4: Project Topographic Surface, Elevations in feet referenced to local project datum Figure 5: Project Land Cover Types and Manning’s Roughness

Appendices

Appendix A: Hydrologic Analyses Appendix B: Hydraulic Analyses

Page 1 CA2020(1) San Vicente Bridges - Hydraulic Report

1 PROJECT BACKGROUND INFORMATION

The San Vicente Bridges project is located in Santa Cruz County within the Bureau of Land Management (BLM) Cotoni-Coast Dairies National Monument. The proposed project will replace one bridge carrying San Vicente Road over San Vicente Creek (Bridge 1) and remove a bridge over San Vicente Creek (Bridge 2), see Figure 1. Bridge 1 consists of a 29-foot long structure with a timber deck on four steel girders.

Bridge 2 consists of a 40-foot long structure with a timber deck on a steel railcar superstructure with two steel girders. Detailed hydrologic and hydraulic analysis was conducted for only for Bridge 1 since Bridge 2 entails removal of the existing structure only. Details of the analysis for Bridge 1 are presented in the following sections.

Figure 1: Project location map.

Page 2 CA2020(1) San Vicente Bridges - Hydraulic Report

2 HYDRAULIC DESIGN CRITERIA

The Federal Lands Highway Project Development and Design Manual (PDDM) (Federal Lands Highway 2012) establishes the hydraulic design criteria. Based on the project scoping report the road is currently closed to the public, has an average daily traffic (ADT) of less than 100 vehicles, and no posted speed.

Although based on these parameters the road is classified as low standard road for hydraulic design purposes, bridge capacity and scour criteria apply equally to both high and low standard roads. The PDDM design criteria are listed in Table 1.

Table 1: PDDM Hydraulic Design Criteria

Road Classification: Low-Standard Road Bridges:

Design Frequency Check Frequency Freeboard

50-year flood Greater of 100-year or overtopping flood

• Minimum of 2 feet

• 3.5 feet to 5 feet when woody debris potential is significant

• 5 feet to 10 feet when ice flow potential is significant

Floodplain Encroachment FEMA SFHA Involvement Allowable Rise

Project not within FEMA regulated special flood hazard area (SFHA)

Maximum 1-foot rise in water surface profile over existing conditions

Scour:

Scour Design

Frequency Scour Check Frequency Scour Countermeasure Design Frequency

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

According to the BLM, the proposed bridge will only be used for BLM access and not open to public vehicular travel. Based on the hydraulic analysis conducted for the project described in the following sections the existing bridge is undersized and can only pass a 2-year storm event with freeboard. Due to the site constraints a reduced capacity design criterion was applied to the project as shown in Table 2.

Table 2: Project Hydraulic Design Criteria

Design Frequency Check Frequency Freeboard 5-year flood 10-year flood Minimum of 1 foot

Page 3 CA2020(1) San Vicente Bridges - Hydraulic Report

3 HYDROLOGY

3.1 HYDROLOGIC SETTING

The project is located within the San Vicente Creek Sub-watershed (HUC12: 180500060304), see Figure 2.

San Vicente Creek generally flows southwest from its headwaters at Ben Lomond Mountain to the mouth at the Pacific Ocean near Davenport, CA. The contributing drainage basin to Bridge 1 was delineated using available 10-meter digital elevation model (DEM) information obtained from the USGS National Map. A summary of general basin properties is shown in Table 3.

Figure 2: San Vicente Creek Bridge 1 Basin

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Table 3: San Vicente Creek at Bridge 1 Basin Properties

Stream Crossing Description Drainage Area (mi2) Mean Basin Elevation (ft)

Mean Basin

Slope (%) San Vicente

Creek Existing 29’ Bridge 10.4 1407 25.7

3.2 FEMA FLOOD INSURANCE STUDY

According to FEMA Flood Insurance Rate Map (FIRM) panels 06087C0193F and 06087C0195F the project is located outside of the FEMA special flood hazard area (SFHA). The SFHA comprises the land area that is shown in the FIRM as being inundated by the base flood and where the National Flood Insurance Program's (NFIP) floodplain management regulations apply. An excerpt of the applicable FIRM is shown in Figure 3.

Figure 3: FEMA National Flood Hazard Layer – FIRM Excerpt

Although outside of the FEMA mapped floodplain, the FEMA Flood Insurance Study (FIS) for Santa Cruz County California (Federal Emergency Management Agency 2017) includes a detailed study of San Vicente Creek from the mouth at the Pacific Ocean to approximately 0.5 miles downstream of the project site.

The study used annual peak flow information from 1970 to 1978 from USGS stream gage 11161800 to conduct the hydrologic analysis. The study reported peak flow values at the mouth which has a total

Page 5 CA2020(1) San Vicente Bridges - Hydraulic Report drainage area of 11.3 square miles. The values are shown in Table 4 for reference. Due to the short period of record and updated information available in more recent studies these values were not used for the project.

Table 4: FEMA FIS San Vicente Creek at Mouth Peak Flows

Percent Chance Exceedance (%)

Return Period (year)

San Vicente Creek at Mouth Peak Flow (cfs)

10 10 1,240 2 50 2,340 1 100 2,850

0.2 500 4,140

3.3 AVAILABLE HYDROLOGIC DATA

There are no active USGS streamflow stations within the project limits. There is one inactive station on San Vicente Creek located approximately 2.5 miles upstream from Bridge 1. Table 5 summarizes the station location and period of record. Table 6 shows the flood frequency analysis results for the stream gage obtained from the StreamStats station data collection report (U.S. Geological Survey 2016).

Table 5: Available Peak Streamflow Information

USGS

Station Location Latitude Longitude Drainage

Area Period of Record Years Status

11161800 San Vicente Creek near

Davenport CA 37°03'19" 122°10'52" 6.1 mi2 1970 - 1983 14 Inactive

Table 6: USGS 11161800 Peak Streamflow

Percent Chance Exceedance (%)

Return Period (year)

San Vicente Creek at Bridge 1 Peak Flow (cfs)

50 2 182 20 5 588 10 10 1,020 4 25 1,770 2 50 2,470 1 100 3,280

0.5 200 4,200

0.2 500 5,590

3.4 REGRESSION EQUATION ESTIMATES

The StreamStats web application (U.S. Geological Survey 2016) was used to estimate peak flows for Bridge

1. The California StreamStats application uses the regression equations presented in USGS Report 2012-

Page 6 CA2020(1) San Vicente Bridges - Hydraulic Report

5113 (Gotvald, et al. 2012). The site is located in the North Coast hydrologic region (Region 1). The equations developed for Region 1 relate peak discharge to drainage area and mean annual precipitation, and have average standard errors of prediction that vary from 43 to 59 percent. The results for the Bridge 1 basin are shown in Table 7.

Table 7: StreamStats Peak Discharge Estimates at Project Location

Percent Chance Exceedance (%)

Return Period (year)

San Vicente Creek at Bridge 1 Peak Flow (cfs)

50 2 831 20 5 1,510 10 10 1,980 4 25 2,600 2 50 3,070 1 100 3,550

0.5 200 4,010

0.2 500 4,620

USGS Report 2012-5113 presents a weighting method to improve flood frequency estimates for an ungaged site near a stream gage on the same stream and having a period of record of at least 10 years.

The methodology was applied the Bridge 1 regression estimates using the information from USGS 11161800 described in Section 3.2. The results are summarized in Table 8.

Table 8: Peak Discharge – Weighted Estimates at Project Location using data from USGS 11161800

Percent Chance Exceedance (%)

Return Period (year)

San Vicente Creek at Bridge 1 Peak Flow (cfs)

50 2 1,005 20 5 1,665 10 10 2,067 4 25 2,588 2 50 2,983 1 100 3,401

0.5 200 3,811

0.2 500 4,358

3.5 RECOMMENDED DESIGN DISCHARGES

The recommended design flows for the San Vicente Bridge 1 are shown in Table 9. The unweighted regression equation results were selected since they are slightly more conservative than the weighted regression flows for the less frequent events. Additional details of the hydrologic analysis are provided in Appendix A.

Page 7 CA2020(1) San Vicente Bridges - Hydraulic Report

Table 9: Recommended Design Flows for San Vicente Creek at Bridge 1

Percent Chance Exceedance (%)

Return Period (year)

San Vicente Creek at Bridge 1 Peak Flow (cfs)

50 2 831 20 5 1,510 10 10 1,980 4 25 2,600 2 50 3,070 1 100 3,550

0.5 200 4,010

0.2 500 4,620

4 HYDRAULIC ANALYSIS

4.1 TOPOGRAPHIC INFORMATION

Two sources of topographic information were used to develop the hydraulic model: 2010 LiDAR point cloud obtained from the USGS National Map (U.S. Geological Survey 2018) and field survey information collected by Central Federal Lands in the vicinity of the existing bridge in July 2019. The field survey information was collected in local coordinates referenced to an assumed vertical datum. The vertical datum conversion to the North American Vertical Datum of 1988 (NAVD 88) is approximately negative 893 feet. Since the LiDAR information did not capture the bathymetry of the main channel a channel cross section was estimated upstream and downstream of the limits of field survey. The cross section shape, width, and depth were approximated using the field survey information. The estimated bathymetry of the main channel was incorporated into the project LiDAR topographic data by using the approximate valley slope.

The field survey information was merged with the LiDAR data to obtain a seamless topographic surface for the project as shown in Figure 4. All elevations for the study are in units of feet and are referenced to the local vertical datum. For an approximate conversion to NAVD88 the following equation can be applied:

Elevation in feet NAVD88 = Project elevation in feet – 893 feet.

Page 8 CA2020(1) San Vicente Bridges - Hydraulic Report

Figure 4: Project Topographic Surface, Elevations in feet referenced to local project datum.

4.2 HYDRAULIC MODEL DEVELOPMENT

Two-dimensional hydraulic modeling using SRH-2D (U.S. Bureau of Reclamation 2017) was conducted to estimate water surface elevations and flow velocities in the project reach. The model pre- and post-processing was performed using the SMS 13.0.9 interface (Aquaveo 2019). The model domain extends approximately 1,100 feet upstream to avoid errors associated with the conveyance flow distribution assumption. Downstream the model extends approximately 2,100 feet downstream of the project reach which is just upstream of the FEMA limit of detailed study for San Vicente Creek.

The upstream boundary conditions in the model were specified as steady inflow using the peak flows in Table 9. The downstream boundary condition was specified as a constant water surface elevation. The downstream water surface elevation was estimated using normal depth computations with a slope equal to water surface profile slope obtained from the FEMA flood profile, which is approximately 0.016 ft/ft.

The boundary conditions for various return periods are shown in Table 10.

Table 10: Model Boundary Condiitons

Percent Chance Exceedance (%)

Return Period (year)

Upstream Inflow (cfs)

Downstream WSEL (feet – local datum)

50 2 831 962.09 20 5 1,510 962.68

Bridge 1

Page 9 CA2020(1) San Vicente Bridges - Hydraulic Report

10 10 1,980 963.02 4 25 2,600 963.42 2 50 3,070 963.70 1 100 3,550 963.97

0.5 200 4,010 964.22

0.2 500 4,620 964.52

SRH-2D uses Manning’s “n” values to calculate bed friction. The land use types were delineated from aerial imagery as shown in Figure 5 and assigned typical roughness values. The roughness values used in the model are shown in Table 11.

Table 11: Recommended Design Flows for San Vicente Creek at Bridge 1

Land Use Manning's "n" Main Channel 0.035

Floodplain Pasture 0.030 Floodplain Trees 0.100 Floodplain Brush 0.060

Page 10 CA2020(1) San Vicente Bridges - Hydraulic Report

Figure 5: Project Land Cover Types and Manning’s Roughness

4.3 HYDRAULIC MODEL RESULTS

4.3.1 Existing Conditions

Existing conditions hydraulic simulations using the parameters described in Section 4.2 were conducted for the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year return periods. The existing bridge geometry was obtained from the field survey information. The existing bridge has an approximate low chord of 998.1 feet and an approximate 23 feet bridge opening. The existing conditions results are summarized in Table 12 and Table 13, at the upstream bridge face and an upstream cross section spanning the entire floodplain width, respectively. The results show that the existing bridge has capacity to pass a 2-year peak flow with freeboard along a portion of the bridge. Bridge pressure flow, where the flow impinges on the low chord, and overtopping of the approaches occur at a 5-year peak flow and above. Additional details of the hydraulic analyses are provided in Appendix B.

Bridge 1

Page 11 CA2020(1) San Vicente Bridges - Hydraulic Report

Table 12: Existing Conditions Hydraulic Results – Bridge Opening at Upstream Bridge Face

Return Period (year) Velocity (ft/s) Depth (ft) WSEL (ft – local datum)

Average Maximum Average Maximum Average Maximum 2 7.22 8.41 5.08 6.51 997.52 998.96 5 8.89 10.15 6.31 7.82 998.78 1000.28

10 6.93 9.46 7.02 8.60 999.49 1001.38 25 7.07 10.52 7.28 8.87 999.75 1002.24 50 7.15 11.15 7.44 9.04 999.91 1002.77

100 7.22 11.70 7.59 9.18 1000.06 1003.25 200 7.30 12.16 7.72 9.31 1000.19 1003.67 500 7.42 12.69 7.87 9.46 1000.34 1004.17

Table 13: Existing Conditions Hydraulic Results – Floodplain Upstream of Bridge

Velocity (ft/s) Depth (ft) WSEL (ft – local datum)

Average Maximum Average Maximum Average Maximum 2 5.68 8.83 4.15 6.85 997.85 998.33 5 3.68 9.53 3.23 9.37 1000.81 1001.25

10 3.95 7.86 3.08 11.45 1002.28 1002.66 25 4.77 8.49 3.46 12.20 1002.86 1003.41 50 5.40 8.87 3.86 12.66 1003.26 1003.87

100 5.86 9.21 4.10 13.08 1003.55 1004.29 200 6.08 9.53 4.21 13.43 1003.87 1004.65 500 6.54 9.92 4.46 13.87 1004.17 1005.09

4.3.2 Proposed Conditions

Proposed conditions hydraulic simulations using the parameters described in Section 4.2 were conducted for the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year return periods. For the proposed conditions model the proposed bridge was assumed to have a low chord elevation of 1000.3 feet and a bridge opening of approximately 46 feet. The proposed conditions results are summarized in Table 14 and Table 15 at the upstream bridge face and an upstream cross section spanning the entire floodplain width, respectively.

The results show that the proposed bridge has capacity to pass a 5-year peak flow with freeboard along the entire low chord. The proposed bridge has capacity to pass a 10-year peak flow with partial freeboard, although overtopping of the approaches occurs. Bridge pressure flow, where the flow impinges on the low chord, and overtopping of the approaches occur at a 25-year peak flow and above. Additional details of the hydraulic analyses are provided in Appendix B.

Page 12 CA2020(1) San Vicente Bridges - Hydraulic Report

Table 14: Proposed Conditions Hydraulic Results – Bridge Opening at Upstream Bridge Face

Velocity (ft/s) Depth (ft) WSEL (ft – local datum)

Average Maximum Average Maximum Average Maximum 2 5.51 9.38 4.07 5.15 996.61 997.39 5 7.41 11.39 5.43 6.82 997.98 999.29

10 8.17 12.67 5.84 7.65 998.57 1000.44 25 9.29 13.34 6.57 8.23 999.3 1001.13 50 9.85 13.44 7.03 8.5 999.76 1001.60

100 10.33 13.41 7.42 8.69 1000.15 1002.03 200 10.69 13.37 7.71 8.85 1000.44 1002.38 500 11.19 13.38 8.03 9.05 1000.76 1002.76

Table 15: Proposed Conditions Hydraulic Results – Floodplain Upstream of Bridge

Velocity (ft/s) Depth (ft) WSEL (ft – local datum)

Average Maximum Average Maximum Average Maximum 2 6.66 11.25 3.39 4.34 996.54 997.21

5 8.71 13.10 4.53 5.91 997.90 998.98

10 5.75 14.28 2.86 6.66 999.76 1001.43

25 5.33 14.87 2.46 7.62 1001.03 1002.33

50 5.78 14.89 2.77 8.30 1001.56 1002.80

100 6.49 14.90 3.22 8.91 1002.01 1003.20

200 6.68 15.01 3.36 9.43 1002.40 1003.55

500 6.99 15.31 3.69 10.34 1002.90 1004.01

Freeboard was evaluated for the average and maximum water surface elevations at the bridge face. The San Vicente watershed is mostly forested therefore debris is a concern and freeboard should be maximized as practicable. The results are summarized in Table 16, negative values indicate that water surface elevation is above the bridge low chord and are highlighted in red.

Table 16: Proposed Conditions Freeboard

Return Period (year)

Proposed Bridge Low Chord (ft – local datum)

WSEL (ft – local datum) Freeboard

Average Maximum Average Maximum

2 1000.3 996.61 997.39 3.7 2.9 5 1000.3 997.98 999.29 2.3 1.0

10 1000.3 998.57 1000.44 1.7 -0.1 25 1000.3 999.3 1001.13 1.0 -0.8 50 1000.3 999.76 1001.60 0.5 -1.3

100 1000.3 1000.15 1002.03 0.1 -1.7

Page 13 CA2020(1) San Vicente Bridges - Hydraulic Report

200 1000.3 1000.44 1002.38 -0.1 -2.1 500 1000.3 1000.76 1002.76 -0.5 -2.5

A comparison of the average and maximum 100-year water surface elevations upstream of the bridge is shown in Table 17. The results show that the 100-year water surface elevation is being reduced with the proposed bridge, therefore the floodplain encroachment criteria for an unregulated zone is satisfied.

Table 17: Proposed vs Existing 100-Year Water Surface Elevations

Return Period (year) WSEL (ft – local datum)

Average Maximum Existing 100-year 1003.55 1004.29

Proposed 100-year 1002.01 1003.20

Difference (Proposed – Existing) -1.54 -1.09

4.4 SCOUR CONSIDERATIONS

The proposed bridge abutments will consist of vertical concrete abutment walls on founded on shallow spread footings. The footings will extend to embedment on non-erodible bedrock. The footing depths were estimated based on the geotechnical investigation conducted for the project which found shallow bedrock at both abutment locations (see Geotechnical Report). Due to the presence of shallow bedrock contraction scour and local abutment scour depths were not estimated. It is assumed that during large flood events streambed material will be mobilized and scoured to bedrock elevation. The proposed bridge has been designed to withstand pressure flows from a 100-year flood event.

5 RECOMMENDATIONS

Hydrology and hydraulics analyses were conducted for the San Vicente Bridge 1 location. Based on the hydraulic results the following bridge geometry is recommended:

• Proposed bridge low chord of 1000.3 feet (local datum).

• Proposed bridge waterway opening width of 46 feet.

• Proposed abutments founded on non-erodible bedrock.

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6 REFERENCES

Aquaveo. 2019. Surface-water Modeling System (SMS), version 13.0.5. Provo, UT.

Bonnin, Geoffrey M., Deborah Martin, Bingzhang Lin, Tye Parzybok, Michael Yekta, and David Riley. 2011.

"Precipitation-Frequency Atlas of the United States, Semiarid Southwest (Arizona, Southeast California, Nevada, New Mexico, Utah)." NOAA Atlas 14, Volume 1, National Oceanic and Atmospheric Administration , Silver Springs, MD.

Federal Emergency Management Agency. 2017. "Flood Insurance Study Santa Cruz County, California and Incorporated Areas." Flood Insurance Study Number 06087CV001C.

Federal Highway Administration. 2017. HY-8 Culvert Analysis Program. Version 7.50.

Federal Highway Administration. 2002. Hydraulic Design Series No. 2, Second Edition, FHWA -NHI-02-001.

Washington, DC: Federal Highway Administration.

Federal Lands Highway. 2012. "Project Development and Design Manual, Chapter 7 Hydrology and Hydraulics." https://flh.fhwa.dot.gov/resources/design/pddm/.

Gotvald, Anthony J., Nancy A. Barth, Andrea G. Veilleux, and Charles Parrett. 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.

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

Kenney, Terry A., Chris D. Wilkowske, and Shane J. Wright. 2008. "Methods for Estimating Magnitude and Frequency of Peak Flows for Natural Streams in Utah." Scientific Investigations Report 2007-5158, U.S. Geological Survey. https://pubs.usgs.gov/sir/2007/5158/.

Multi-Resolution Land Characteristics Consortium . 2018. National Land Cover Database 2011 (NLCD 2011). Multi-Resolution Land Characteristics Consortium (MRLC).

https://data.nal.usda.gov/dataset/national-land-cover-database-2011-nlcd-2011.

National Oceanic and Atmospheric Administration. 2011. Precipitation Frequency Data Server (PFDS).

Silver Springs, MD. Accessed April 2019. https://hdsc.nws.noaa.gov/hdsc/pfds/index.html.

Natural Resources Conservation Service. 1997. "National Engineering Handbook, Part 630 Hydrology."

Washington, DC. https://directives.sc.egov.usda.gov/viewerFS.aspx?hid=21422.

Natural Resources Conservation Service. 2015. Soil Survey Geographic (SSURGO) database. Fort Worth, TX. Accessed April 2019. http://websoilsurvey.nrcs.usda.gov.

U.S. Army Corps of Engineers. 2017. HEC-HMS, Hydrologic Engineering Center Hydrologic Modeling System. Version 4.2.1. Davis, CA.

U.S. Bureau of Reclamation. 2017. SRH-2D, Sedimentation and River Hydraulics – Two-Dimensional model.

Version 3.2.

U.S. Geological Survey. 2016. StreamStats Program. http://streamstats.usgs.gov.

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U.S. Geological Survey. 2018. The National Map. Accessed March 2019.

https://viewer.nationalmap.gov/advanced-viewer/.

Utah Department of Transportation. 2018. "Drainage Manual of Instruction."

https://www.udot.utah.gov/main/f?p=100:pg:0:::1:T,V:5107.

CA2020(1) San Vicente Bridges - Hydraulic Report

Appendix A – Hydrologic Analyses

USGS 11161800 Data Collection Report

7/18/2019 StreamStats Data-Collection Station Report https://streamstatsags.cr.usgs.gov/gagepages/html/11161800.htm 1/4

StreamStats Data-Collection Station Report

USGS Station Number 11161800 Station Name SAN VICENTE C NR DAVENPORT CA

Click here to link to available data on NWIS-Web for this site.

Descriptive Information

Station Type Streamgage, continuous record Location Gage Regulation and Diversions Regulated? False Period of Record Remarks Latitude (degrees NAD83) 37.05522644 Longitude (degrees NAD83) -122.18219011 Hydrologic unit code 18060001 County - HCDN2009 No

Physical Characteristics

Characteristic Name Value Units Citation Number

Descriptive Information High_Flow_Region_Code 1 dimensionless 230 High_Flow_Regression_Equation Y Yes or No 230 Datum_of_Latitude_Longitude NAD83 dimensionless 30 District_Code 06 dimensionless 30 Begin_date_of_record 10/1/1969 days 41 End_date_of_record 9/30/1985 days 41 Number_of_days_of_record 5844 days 41 Number_of_days_GT_0 5834 days 41 Precipitation Statistics 24_Hour_2_Year_Precipitation 5.8000 inches 31 Mean_Annual_Precipitation 63.84 inches 230 Topographical Characteristics Mean_Basin_Elevation 1655 feet 230 Land Cover Characteristics Percent_Forest 95.000 percent 31 Percent_Storage 0.0000 percent 31 Stream Channel Properties Main_Channel_Length 5.5000 miles 31 Stream_Slope_10_and_85_Method 330.000 feet per mi 31 Basin Dimensional Characteristics Contributing_Drainage_Area 6.0700 square miles 31 Drainage_Area 6.1 square miles 230

Streamflow Statistics

Years Standard Error, Lower 95% Upper 95% http://nwis.waterdata.usgs.gov/nwis/inventory/?site_no=11161800 https://streamstatsags.cr.usgs.gov/gagepages/html/11161800.htm 2/4

Statistic Name Value Units Citation Number Preferred?

of Record percent Variance log-

Confidence Interval

Confidence Interval

Peak-Flow Statistics Mean_Annual_Flood 40.400 cubic feet per second 31 Y

2_Year_Peak_Flood 182 cubic feet per second

230 Y 14 42.01 0.0306499992

5_Year_Peak_Flood 588 cubic feet per second

230 Y 14 42.76 0.0316659994

10_Year_Peak_Flood 1020 cubic feet per second

230 Y 14 47.93 0.0390110016

25_Year_Peak_Flood 1770 cubic feet per second

230 Y 14 57.16 0.0533300005

50_Year_Peak_Flood 2470 cubic feet per second

230 Y 14 65.43 0.0672049969

100_Year_Peak_Flood 3280 cubic feet per second

230 Y 14 74.66 0.0835679993

200_Year_Peak_Flood 4200 cubic feet per second

230 Y 14 84.88 0.10234

500_Year_Peak_Flood 5590 cubic feet per second

230 Y 14 100 0.13074

Regression_2_Year_Peak_Flood 555 cubic feet per second

230 Y 58.18 0.0549839996

Regression_5_Year_Peak_Flood 998 cubic feet per second

230 Y 47.03 0.037684001

Regression_10_Year_Peak_Flood 1310 cubic feet per second

230 Y 44.02 0.0334010012

Regression_25_Year_Peak_Flood 1720 cubic feet per second

230 Y 42.21 0.0309289992

Regression_50_Year_Peak_Flood 2020 cubic feet per second

230 Y 42.29 0.031033

Regression_100_Year_Peak_Flood 2340 cubic feet per second

230 Y 43.78 0.0330809988

Regression_200_Year_Peak_Flood 2640 cubic feet per second

230 Y 43.96 0.033321999

Regression_500_Year_Peak_Flood 3040 cubic feet per second

230 Y 45.53 0.0355289988

Weighted_5_Year_Peak_Flood 748 cubic feet per second

230 Y 30.91 0.0172070004

Weighted_10_Year_Peak_Flood 1170 cubic feet per second

230 Y 31.64 0.0179939996

Weighted_25_Year_Peak_Flood 1740 cubic feet per second

230 Y 33.07 0.019576

Weighted_50_Year_Peak_Flood 2160 cubic feet per second

230 Y 34.52 0.0212299991

Weighted_100_Year_Peak_Flood 2580 cubic feet per second

230 Y 36.59 0.0237000007

Weighted_200_Year_Peak_Flood 2960 cubic feet per second

230 Y 37.7580722602945 0.025138

Weighted_500_Year_Peak_Flood 3460 cubic feet per second

230 Y 39.96 0.0279370006

Peak_years_with_historic_adjustment 14 years 230 N Weighted_2_Year_Peak_Flood 271 cubic feet per second 230 Y 33.16 0.0196800008

Flow-Duration Statistics 1_Percent_Duration 86 cubic feet per second 325 Y 16

2_Percent_Duration 60 cubic feet per second

325 Y 16

3_Percent_Duration 46 cubic feet per second

325 Y 16

5_Percent_Duration 32 cubic feet per second

325 Y 16 https://streamstatsags.cr.usgs.gov/gagepages/html/11161800.htm 3/4

10_Percent_Duration 20 cubic feet per second

325 Y 16

15_Percent_Duration 15 cubic feet per second

325 Y 16

20_Percent_Duration 12 cubic feet per second

325 Y 16

25_Percent_Duration 8.8 cubic feet per second

325 Y 16

30_Percent_Duration 7 cubic feet per second

325 Y 16

35_Percent_Duration 5.8 cubic feet per second

325 Y 16

40_Percent_Duration 4.8 cubic feet per second

325 Y 16

45_Percent_Duration 4 cubic feet per second

325 Y 16

50_Percent_Duration 3.3 cubic feet per second

325 Y 16

55_Percent_Duration 2.9 cubic feet per second

325 Y 16

60_Percent_Duration 2.5 cubic feet per second

325 Y 16

65_Percent_Duration 2.1 cubic feet per second

325 Y 16

70_Percent_Duration 1.9 cubic feet per second

325 Y 16

75_Percent_Duration 1.6 cubic feet per second

325 Y 16

80_Percent_Duration 1.5 cubic feet per second

325 Y 16

85_Percent_Duration 1.2 cubic feet per second

325 Y 16

90_Percent_Duration 0.9 cubic feet per second

325 Y 16

95_Percent_Duration 0.69 cubic feet per second

325 Y 16

97_Percent_Duration 0.6 cubic feet per second

325 Y 16

98_Percent_Duration 0.5 cubic feet per second

325 Y 16

99_Percent_Duration 0.42 cubic feet per second

325 Y 16

Annual Flow Statistics Mean_Annual_Flow 9.4 cubic feet per second 325 Y 16

Stand_Dev_of_Mean_Annual_Flow 7.3 cubic feet per second

325 Y 16

Maximum_Annual_Mean_Flow 25 cubic feet per second

325 Y 16

Minimum_Annual_Mean_Flow 0.83 cubic feet per second

325 Y 16

General Flow Statistics Minimum_daily_flow 0 cubic feet per second 325 Y 16

Maximum_daily_flow 854 cubic feet per second

325 Y 16

Std_Dev_of_daily_flows 26 cubic feet per second

325 Y 16

Average_daily_streamflow 9.378 cubic feet per second

41 Y 16

Harmonic_Mean_Streamflow 2.1 cubic feet per second

325 Y 16

Mean_of_Logs_of_Daily_Values 0.596943 Log base 10 325 Y 16 https://streamstatsags.cr.usgs.gov/gagepages/html/11161800.htm 4/4

Std_Dev_of_Logs_of_Daily_Values 0.523251 Log base 10 325 Y 16 Skew_of_Logs_of_Daily_Values 0.472232 Log base 10 325 Y 16 Non_Zero_Adjusted_Harmonic_Mean_Flow 2.1 cubic feet per second 325 Y 16

Base Flow Statistics Number_of_years_to_compute_BFI 16 years 42 Y 16 Average_BFI_value 0.647 dimensionless 42 Y 16 Std_dev_of_annual_BFI_values 0.119 dimensionless 42 Y 16 Probabillity Statistics Probability_flow_durations_are_zero 0.001711 dimensionless 325 Y 16

Citations

Citation Number

Citation Name and URL

31 Imported from Basin Characteristics file 41 Wolock, D.M., 2003, Flow characteristics at U.S. Geological Survey streamgages in the conterminous United States:

U.S. Geological Survey Open-File Report 03-146, digital data set 42 Wolock, D.M., 2003, Base-flow index grid for the conterminous United States: U.S. Geological Survey Open-File

Report 03-263, digital data set 230 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.

325 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.

http://water.usgs.gov/GIS/metadata/usgswrd/XML/qsitesdd.xml http://pubs.water.usgs.gov/ofr03263/

StreamStats Output

7/18/2019 StreamStats https://streamstats.usgs.gov/ss/ 1/3

San Vicente Creek - Bridge 1

Basin Characteristics

Parameter Code Parameter Description Value Unit

BASINPERIM Perimeter of the drainage basin as defined in SIR 2004-5262

23.3 miles

BSLDEM30M Mean basin slope computed from 30 m DEM 25.7 percent

CENTROIDX Basin centroid horizontal (x) location in state plane coordinates

-2275707.8 feet

CENTROIDY Basin centroid vertical (y) location in state plane units 1873345.8 feet

DRNAREA Area that drains to a point on a stream 10.4 square miles

Region ID: CA Workspace ID: CA20190718193709930000 Clicked Point (Latitude, Longitude): 37.02411, -122.18610 Time: 2019-07-18 13:37:38 -0600 https://streamstats.usgs.gov/ss/ 2/3

Parameter Code Parameter Description Value Unit

EL6000 Percent of area above 6000 ft 0 percent

ELEV Mean Basin Elevation 1407 feet

ELEVMAX Maximum basin elevation 2649 feet

FOREST Percentage of area covered by forest 66.9 percent

JANMAXTMP Mean Maximum January Temperature 56.42 degrees F

JANMINTMP Mean Minimum January Temperature 42.85 degrees F

LAKEAREA Percentage of Lakes and Ponds 0 percent

LC11DEV Percentage of developed (urban) land from NLCD 2011 classes 21-24

6.8 percent

LC11IMP Average percentage of impervious area determined from NLCD 2011 impervious dataset

0.2 percent

LFPLENGTH Length of longest flow path 9 miles

MINBELEV Minimum basin elevation 101 feet

OUTLETELEV Elevation of the stream outlet in thousands of feet above NAVD88.

102 feet

PRECIP Mean Annual Precipitation 58.9 inches

RELIEF Maximum - minimum elevation 2548 feet

RELRELF Basin relief divided by basin perimeter 109 feet per mi

Peak-Flow Statistics Parameters[2012 5113 Region 1 North Coast]

Parameter Code Parameter Name Value Units Min Limit Max Limit

DRNAREA Drainage Area 10.4 square miles 0.04 3200

PRECIP Mean Annual Precipitation 58.9 inches 20 125

Peak-Flow Statistics Flow Report[2012 5113 Region 1 North Coast]

PIl: Prediction Interval-Lower, PIu: Prediction Interval-Upper, SEp: Standard Error of Prediction, SE:

Standard Error (other -- see report)

Statistic Value Unit PIl PIu SEp https://streamstats.usgs.gov/ss/ 3/3

Statistic Value Unit PIl PIu SEp

2 Year Peak Flood 831 ft^3/s 342 2020 58.6

5 Year Peak Flood 1510 ft^3/s 722 3140 47.4

10 Year Peak Flood 1980 ft^3/s 987 3980 44.2

25 Year Peak Flood 2600 ft^3/s 1340 5060 42.7

50 Year Peak Flood 3070 ft^3/s 1580 5990 42.7

100 Year Peak Flood 3550 ft^3/s 1780 7090 44.3

200 Year Peak Flood 4010 ft^3/s 2000 8020 44.4

500 Year Peak Flood 4620 ft^3/s 2250 9460 46

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: 4.3.8 http://pubs.usgs.gov/sir/2012/5113/

Weighted Regression

Weighted peak flow estimates using regression equations and USGS Station 11161800:

Return Period Au Ag A Qp(g)w Qp(g)r Qp(u)r Qp(u)w

(yr) (sq. mi.) (sq.mi.) (sq. mi.) (cfs) (cfs) (cfs) (cfs)

2 10.4 6.1 4.3 271 555 831 1,005

5 10.4 6.1 4.3 748 998 1,510 1,665

10 10.4 6.1 4.3 1,170 1,310 1,980 2,067

25 10.4 6.1 4.3 1,740 1,720 2,600 2,588

50 10.4 6.1 4.3 2,160 2,020 3,070 2,983

100 10.4 6.1 4.3 2,580 2,340 3,550 3,401

200 10.4 6.1 4.3 2,960 2,640 4,010 3,811

500 10.4 6.1 4.3 3,460 3,040 4,620 4,358

Reference: Gotvald, Anthony J., Nancy A. Barth, Andrea G. Veilleux, and Charles Parrett. 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.

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

CA2020(1) San Vicente Bridges - Hydraulic Report

Appendix B - Hydraulic Analyses

Existing Conditions SRH‐2D Results

Excerpt of SRH‐2D Computational Mesh at Bridge Site

Existing Bridge

2‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

5‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

10‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

25‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

50‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

100‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

200‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

500‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

Proposed Conditions SRH‐2D Results

Excerpt of SRH‐2D Computational Mesh at Bridge Site

Proposed Bridge

2‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

5‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

10‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

25‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

50‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

100‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

200‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

500‐Year WSEL Results and Velocity Vectors (feet ‐ local datum)

4.4 Scour Considerations

4.4 Scour Considerations