FEMA Region IX Hydrologic Analyses Contra Costa County, California CONTRACT NUMBER: HSFEHQ 09 D 0368 TASK ORDER HSFE09 09 J 0001 October 2011
Document History Document Location Location Z:\Risk MAP Production\REGION 9\CALIFORNIA\CONTRA COSTA COUNTY\09 09 3059S\Hydrology Revision History Version Number Version Date Summary of Changes Team/Author 01 04/11/2011 1 st Draft K. Labuhn 02 10/1/2011 Client Distribution Name Title/Organization Location Eric Simmons FEMA MIP, see Appendix C. http://www.bakeraecom.com/index.php/california/contracosta-county/
Table of Contents 1. TASK SUMMARY... 1 1.1. INTRODUCTION... 1 1.2. SCOPE OF WORK... 1 1.3. UPDATES TO SCOPE OF WORK... 1 2. WATERSHED LOCATIONS AND DESCRIPTIONS... 1 2.1. BRUSHY CREEK... 1 2.2. FRISK CREEK... 1 2.3. KELLOGG CREEK... 2 2.4. MT. DIABLO CREEK... 3 2.5. DEM PREPROCESSING... 4 2.6. HEC-GEOHMS SUBBASIN DELINEATION... 5 2.7. HEC-HMS MODEL SETUP... 5 2.7.1. SOIL MOISTURE ACCOUNTING LOSS METHOD... 5 2.7.2. USER SPECIFIED S-CURVE TRANSFORM METHOD... 6 2.7.3. BASEFLOW METHOD... 7 2.7.4. RESERVOIRS... 7 2.7.5. REACHES... 7 2.7.6. RAINFALL DATA AND DISTRIBUTION... 7 2.8. MARSH CREEK... 8 3. RESULTS... 9 3.1. COMPARISON TO PREVIOUS FLOW CALCULATIONS... 10 Appendices Appendix A Appendix B Appendix C Appendix D Hydrologic Analysis Appendices A 1 Landuse and Infiltration Rate Calculations A 2 Lag Time Calculations A 3 Reservoir Information A 4 Reach Information TSDN Documents B 1 Deliverables Checklist B 2 Contact Report List B 3 Hydrologic Analyses Index B 4 Certification of Compliance C 1 Hydrologic Analyses QA/QC Reviews Digital Data on the MIP May 2011 i
1. Task Summary 1.1. Introduction Contra Costa County, California Hydrologic Analyses BakerAECOM has completed the Hydrologic Analyses activities in accordance with Task Order HSFE09 09 J 0001 for Contra Costa County, California under Contract No. HSFEHQ 09 D 0368. The project location and a detailed map of the county are shown in Figure 1. 1.2. Scope of Work Scope: The primary tasks are to conduct detailed hydrologic analyses of four streams (Brushy, Frisk, Kellogg and Mt. Diablo Creeks), update previous model for Marsh Creek and to perform QC of the study currently being conducted by the county for Wildcat and San Pablo Creeks. Specific tasks will include: Compare discharges calculated by the county against results of the HEC HMS model for Brushy, Frisk, Mt. Diablo and Kellogg Creeks Update the HEC HMS model for Marsh Creek to reflect existing landuse conditions (based on the 2008 aerial photos provided by the county) and edit the storage data on Sand Creek to reflect existing conditions Review the hydrologic analysis conducted by the county for Wildcat and San Pablo Creeks as part of the levee certification process Standards: Hydrologic Data Development work shall be performed in accordance with the standards specified in Section 4 Standards. The DCS must be met for this deliverable to be acceptable. Deliverables: BakerAECOM shall make the products available to FEMA and any other deliverables associated with this activity that are defined in the updated Appendix M (Data Capture Standards) by uploading the digital data to the MIP. 1.3. Updates to Scope of Work The hydrologic analysis submitted by Contra Costa County for Wildcat and San Pablo Creeks is not currently included in this document. July 2011 1
Figure 1. Scoping Map July 2011 1
2. Watershed Locations and Descriptions 2.1. Brushy Creek Figure 2 below shows the Brushy Creek watershed. The creek begins in the Canada de los Vaqueros hills near the border of Contra Costa and Alameda Counties and flows in a generally north to northeast direction until its confluence with Clifton Court Forebay. The watershed is approximately 16.4 square miles and is composed mostly of public lands/open space, agricultural lands and some low density residential development. The Byron Airport is partially located within the Brushy Creek watershed. Figure 2. Brushy Creek Watershed 2.2. Frisk Creek Figure 3 below shows the Frisk Creek watershed. The creek begins in the Canada de los Vaqueros hills and flows in a generally north to northeast direction until it reach the east side of Byron Highway where it turns and flows due north to its confluence with Discovery Bay. The watershed is approximately 12.2 square miles and is composed mostly of public lands/open space, agricultural lands and some low density residential development. The community of Byron is located in the Frisk Creek watershed. July 2011 1
Figure 3. Frisk Creek Watershed 2.3. Kellogg Creek Figure 4 below shows the Kellogg Creek watershed. The Los Vaqueros Reservoir is a drinking water storage reservoir that also captures the upstream flows from Kellogg Creek. Kellogg Creek flows in a generally northern direction until just south of Marsh Creek Road (Highway 4) where it turns to the south and then flows east through a manmade watercourse to its confluence with Discovery Bay. The watershed is approximately 32.2 square miles and is composed mostly of public lands/open space, agricultural lands and some low density residential development. July 2011 2
Figure 4. Kellogg Creek Watershed 2.4. Mt. Diablo Creek Mt. Diablo Creek starts in the Mount Diablo State Park and flows to the northwest to its confluence with Suisun Bay. The watershed is located in the City of Concord and Contra Costa County and encompasses land that was part of the former Concord Naval Weapons Base. That base has been decommissioned and will eventually become property of the City of Concord and the county. The watershed is 32.7 square miles and consists of residential and commercial lands in the headwaters and open space on the former Concord Naval Weapons Base lands. Mt. Diablo Creek was studied previously by FEMA but that study ended at Bailey Road and did not show any flood hazards on the Naval Weapons Base. This study is intended to determine the flood hazards downstream of Kirker Pass Road to Mt. Diablo Creek s confluence with Suisun Bay. July 2011 3
2.5. DEM Preprocessing Figure 5. Mt. Diablo Creek Watershed Since Brushy, Frisk and Kellogg Creeks are adjacent to one another the tile digital elevation models (DEMs) provided by Contra Costa County were mosaiced together to create one DEM to use for the analysis. There were some areas where the tiles did not meet each other and there were other small areas of missing data. In order to fill in the missing elevation data from some grid cells the raster calculator focalmean function was used. The focalmean function looks at the elevation data in the cells surrounding the empty cell and calculates a mean value for that empty cell. In this case the focalmean statement was written to look at a 3 cell by 3 cell rectangle surrounding the empty cell and calculate the mean. This filled in the necessary missing data in the DEM and could then be used for further analysis. A similar process was used to construct a DEM for the Mt. Diablo Creek watershed. July 2011 4
2.6. HEC-GeoHMS Subbasin Delineation Once the DEMs were constructed the next step was to delineate the subbasins for each creek. In order to do this the ArcGIS extension HEC GeoHMS was used. The standard process for HEC GeoHMS was followed including performing a fill operation to fill in the sink in the DEMs and then the tools were run to define the streams and determine the subbasins. Once the draft streams and subbasins were determined a manual review of the stream locations and subbasins was completed and a number of edits were made to correct the automated process. In particular, the DEMs did not always locate the streams correctly as shown on the provided aerial photos so these were corrected and the subbasins edited manual as needed. Some of the smaller subbasins were combined and a few were split at points were flows were needed. 2.7. HEC-HMS Model Setup A number of discussions were held with Contra Costa County to determine which loss and transform methods would be most appropriate for use in the county. Typically FEMA will use the NRCS curve number and unit hydrograph method but Contra Costa County has a large library of data concerning the hydrology of the county. They have provided guidance regarding methods that have been used previously in the county to calculate flows. A review of these methods (Reference 1) shows that they are appropriate for in this project. The loss method used is the Soil Moisture Accounting method and the transform method is the User Specific S curve. The necessary inputs for these methods are land use and Manning s n data. The only exception to this methodology was for subbasin 1 in the Kellogg Creek watershed. Subbasin 1 is the direct drainage area to the Los Vaqueros Reservoir and for this subbasin the NRCS methods were used. The curve number and lag time were obtained from the HEC 1 model completed for a previous LOMR submittal (case number 03 09 0909P). Additionally, Mt. Diablo Creek was previously studied by FEMA and there are an effective discharge values available, with the most downstream available discharge at Bailey Road. In order to determine if this flow was still reasonable two models were created for Mt. Diablo Creek. The first followed the methods described in this section and the section treated the flow upstream of Bailey Road as a constant source input using the effective flow. 2.7.1. Soil Moisture Accounting Loss Method The Soil Moisture Accounting loss method in HEC HMS allows for a number of inputs including storage in different units such as canopy, surface, soil and groundwater storage. For flood events the only inputs that would have an appreciable impact on flows are the infiltration rate and soil storage amount (or initial infiltration loss). The County provided BakerAECOM with a conversion chart that links landuse with minimum, average and maximum infiltration rates. For the Brushy, Frisk, Kellogg and Mt. Diablo Creek watersheds the landuse shapefile was intersected with the subbasin shapefile to find the landuse by subbasin. Then area weighted average infiltration rate was calculated based on the average values provided by the County. Appendix A 1 provides tables of this data. The initial infiltration loss was set to a standard 0.25 inches which comes from the County s standard. July 2011 5
Contra Costa County provided BakerAECOM with a landuse shapefile names GPLU_Edited. As discussed with the County, this is a shapefile of landuse designations that come from the Contra Costa County general plan and also from information provided by the incorporated cities in the County. This shapefile is of the zoned/planned landuse (i.e., future conditions), not necessarily how the land is currently being used. Since FEMA models existing, not future conditions, the landuse categories were reviewed against the aerial photos provided by the County to determine if the planned landuse compared to the current landuse. In the Frisk and Kellogg Creek watersheds the planned landuse seemed to correspond to the current landuse and no changes were made. The Brushy Creek watershed extends into Alameda County to the south. A review of aerial photos in Alameda County shows no appreciable differences from Contra Costa County so the landuse type associated with subbasins in the Contra Costa County were extended into the subbasins in Alameda County. In the Mt. Diablo Creek watershed the area downstream of Bailey Road was reviewed and it was found that near the Mallard Reservoir there were some areas that are designated as commercial but currently appear to be open space. Additionally, there were a few areas that appeared to be dense residential but were planned as low density residential. Edits were made to the landuse as necessary. Appendix A 1 provides maps and tables showing the breakdown of landuse for each watershed. 2.7.2. User Specified S-Curve Transform Method Contra Costa County uses an S curve that was developed in a 1971 study of Walnut Creek by the U.S. Army Corps of Engineers. This is now the Contra Costa County Flood Control District standard. This curve was reviewed by BakerAECOM and found to be appropriate for use in this study. The curve is input as a percentage curve in HEC HMS as a table of paired data. The other parameter needed is the lag time. The Flood Control District uses the following formula to calculate lag time: 24.. Where: T lag Elapsed time from the centroid (or 50 percent of volume) of the effective rainfall to the centroid (or 50 percent of volume) of the resulting runoff (hours) N weighted watershed Manning s n coefficient L Length of the longest watercourse (miles) L ca Length along that drainage path from a point opposite the centroid of the watershed to the outlet point (miles) S Overall slope of the main watercourse (feet/mile) The length of the stream reaches was calculated using ArcGIS. ArcGIS was also used to find the centroid of each subbasin and a line was then drawn to intersect with the stream centerline. The distance between that point to the outlet, also calculated using ArcGIS, is L ca. The slope was found from creating a contour map of the DEMs and reading the upstream and downstream elevations. July 2011 6
In addition to infiltration rates the County also provided a conversion table between landuse and Manning s n value. Similar to the infiltration rate calculations the area weighted average Manning s n value was calculated for each subbasin. Appendix A 2 contains maps and tables of the data used for these calculations. 2.7.3. Baseflow Method Baseflow is typically not included in calculations of flood events so the baseflow method was set to none for the Brushy, Frisk, Kellogg and Mt. Diablo Creek models. 2.7.4. Reservoirs There are two reservoirs in the studied watersheds. The first is the Los Vaqueros water supply reservoir in the headwaters of Kellogg Creek. The water in this reservoir is delivered and withdrawn by the canal system. This reservoir was previously modeled as part of a Letter of Map Revision case number 03 09 0909P. The storage elevation and outlet information was taken from the HEC 1 model and input into the HEC HMS model (see Appendix A 3). The other reservoir of interest is Mallard Reservoir in the Mt. Diablo Creek watershed. Discussions with the water district (Reference 2) revealed that there are no outlet structures for this reservoir to the creek so it is not included in the modeling effort for Mt. Diablo Creek. 2.7.5. Reaches The Muskingum Cunge method was used to route the flood flows through the watershed. The length and slope were calculated as described in Section 2.5.2. The Manning s n used was based on aerial photos of the area and guidance from Contra Costa County. The bottom width and side slopes were estimated from the two foot topographic data. Appendix A 4 contains tables of the input data. 2.7.6. Rainfall Data and Distribution The SCS method is the rainfall method most commonly used by FEMA. The two parameters necessary are the rainfall distribution curve type (I, IA, II or III) and the storm depth in inches. According to the figures in Appendix B of the NRCS publication Urban Hydrology for Small Watersheds the boundary between the Type I and IA distributions falls approximately through Contra Costa County. The County has reviewed the distributions and compared them to historical analyses done in the county. They have concluded that the Type I distribution is the most appropriate for the County and BakerAECOM agree. The 24 hour rainfall depths were estimated at a midpoint in the watershed and assumed to be an average for the entire watershed. In April 2011 the National Oceanic and Atmospheric Administration (NOAA) released a new analysis of rainfall depths in the western United States that supersedes the data in their publication Atlas 2. Rainfall frequency depths can now be obtained via latitude and longitude from NOAA s website at http://hdsc.nws.noaa.gov/hdsc/pfds/. Table 1 below lists the locations and precipitation frequency estimates obtained from the NOAA website and used in the analysis. July 2011 7
Table 1. Rainfall Frequency Depth Estimates Stream Brushy Creek Frisk Creek Kellogg Creek Mt. Diablo Creek Marsh Creek Location Latitude/longitude At Vasco Road 37.819902 121.655488 At Vasco Road 37.851772 121.648243 At Walnut Boulevard 37.871930 121.699067 At Bailey Road 37.971826 121.969951 At Union Pacific Railroad Crossing 37.942633 121.706373 10% 24 Hour Storm Depth (in) 2% 24 Hour Storm Depth (in) 1% 24 Hour Storm Depth (in) 0.2% 24 Hour Storm Depth (in) 2.53 3.58 4.07 5.31 2.47 3.49 3.96 5.15 2.87 4.02 4.53 5.76 3.33 4.65 5.25 6.70 2.58 3.67 4.18 5.51 2.8. Marsh Creek Contra Costa County provided Baker/AECOM with a HEC HMS model of Marsh Creek but it was completed using future landuse conditions (expected maximum build out) and expansions to the Sand Creek retention basin (Reference 3). Baker/AECOM compared the planned landuse shapefile discussed above in Section 2.5.1 to the aerial photos provided and it was found that there were many locations where the residential development currently built did not match the planned landuse density. For example, there were areas that were planned to be low density residential but the aerial photos showed that high density residential development had already occurred. Numerous changes were made to the land use so that it conformed to the current conditions in the watershed, especially in the residential areas. This resulted in changes to the infiltration rates and Manning s n values as compared to the model provided by the County. Appendices A 1 and A 2 provide further details regarding the changes to the landuse, infiltration rates, and Manning s n values. Baker/AECOM worked closely with the County to modify the elevation storage relationship for the Sand Creek retention basin using the submitted DEM data and GIS software. Additionally, the County provided original construction drawings for the basin to determine the outlet structure geometry and July 2011 8
elevation. Appendix A 3 provides further details regarding the elevation storage calculations and the data regarding the outlets to the basin. Additionally, changes were made to the elevation storage, storage discharge curves for some of the reservoirs in the model, specifically, the Vinyards North and South Reservoirs, Deer Creek Basin, the Fairview Basin, the Freedom Basin, and the Laurel Basin. The changes were made based on a spreadsheet of basin information provided by the county, the DEM data for the Marsh Creek area and best engineering judgment to extrapolate data points from the submitted data. Appendix A 3 has further information regarding the changes made to each reservoir. There is one area in the Marsh Creek watershed, noted as Drainage Area 52D that was included in the submitted HEC HMS model but was ultimately not modeled with HEC HMS due to the complexity of the retention pond hydraulics. This area was modeled using EPASWMM and the County is working to submit the model to BakerAECOM so that that it can be run for the FEMA storm events. Due to the size of the retention ponds it is not expected that these flows will be significant portion of the flow to Marsh Creek but they should be included to document the worst case scenario expected. As soon as the model is received this report will be updated to include those flows. 3. Results The results of the HEC HMS modeling are listed below in Table 2 and Table 3. Table 2. HEC HMS Peak Flows at Junctions for Brushy, Frisk, Kellogg and Mt. Diablo Creeks Flooding Source and Junction Number Drainage Area (square miles) 10% Annual Chance Flood Peak Discharges (cfs) 2% Annual Chance Flood 1% Annual Chance Flood 0.2% Annual Chance Flood Brushy Creek 1 7.027 908.8 1,933.5 2,404.2 3,588.7 2 8.380 1,051.6 2,268.6 2,830.3 4,247.3 3 8.853 1,063.4 2,299.0 2,870.0 4,311.1 4 10.258 1,228.1 2,691.2 3,370.5 5,088.8 5 14.747 1,421.3 3,162.1 3,981.2 6,097.9 Outlet 16.395 1,418.5 3,190.4 4,027.9 6,203.4 Frisk Creek 1 2.635 300.5 651.0 811.9 1,218.9 2 5.585 545.5 1,228.0 1,546.6 2,361.5 3 6.438 587.4 1,356.1 1,716.2 2,639.0 4 2.284 199.6 436.3 545.6 826.4 5 11.364 682.1 1,737.6 2,248.7 3,602.8 Outlet 12.161 498.5 1,430.2 1,899.5 3,175.9 July 2011 9
Flooding Source and Junction Number Drainage Area (square miles) 10% Annual Chance Flood Peak Discharges (cfs) 2% Annual Chance Flood 1% Annual Chance Flood 0.2% Annual Chance Flood Kellogg Creek 1 20.359 417.3 793.5 954.5 1,339.3 2 21.829 676.2 1,315.3 1,591.1 2,250.2 3 25.782 1,090.8 2,235.0 2,739.7 3,963.5 4 27.427 1,164.0 2,465.2 3,051.0 4,485.9 5 28.426 1,137.6 2,466.5 3,070.1 4,592.5 6 30.703 1,142.9 2,560.3 3,210.5 4,882.8 7 31.975 1,163.6 2,644.9 3,333.3 5,108.4 Outlet 32.214 1,152.9 2,626.1 3,311.2 5,083.6 Mt. Diablo Creek Effective Flow 21.832 3,670.0 5,670.0 6,350.0 7,760.0 2 23.080 4,294.3 6,709.7 7,566.8 9,380.6 3 24.210 4,895.2 7,759.3 8,799.9 11,028.4 4 25.209 5,816.2 9,498.2 10,909.4 13,974.6 5 28.058 6,298.8 10,376.9 11,963.1 15,432.5 6 29.918 6,495.9 10,787.5 12,488.7 16,232.8 Outlet 29.943 6,319.5 10,476.9 12,134.1 15,787.2 Location Table 3. Results of HEC HMS Modeling for Marsh Creek at Effective Locations and Road Crossings Drainage Area (square miles) 10% Annual Chance Flood Peak Discharges (cfs) 2% Annual Chance Flood 1% Annual Chance Flood 0.2% Annual Chance Flood At Concord 52.674 498.9 570.9 603.9 780.7 Boulevard At Balfour Road 58.221 918.8 1,365.5 1,568.4 2,117.4 At Central Avenue 65.049 1,169.6 1,755.0 2,017.5 2,699.6 At Union Pacific 81.010 1,721.4 2,751.2 3,678.8 6,204.2 Railroad At Delta Road 85.735 2,202.6 3,703.6 4,398.1 6,610.9 At Santa Fe Railroad 88.984 2,476.2 4,215.0 5,029.1 7,209.4 3.1. Comparison to Previous Flow Calculations The Contra Costa County Flood Control District provided Baker/AECOM with some flow estimates for Frisk, Brushy and Kellogg Creeks and there are flows published for Marsh Creek in the effective FIS. Table 4 below compares the new HEC-HMS flows to those previously calculated. The comparison locations were not exact for Brushy Creek because the Flood Control District calculated the flows to the Southern Pacific Railroad but the HEC-HMS model was not setup to report the flows at that point, instead the flows from the next upstream junction are reported below. July 2011 10
In 2002, a Letter of Map Revision (LOMR) was submitted that included modeling of Kellogg Creek with and without the Los Vaqueros Reservoir in order to revise the floodplain at the downstream end of Kellogg Creek. That LOMR was approved and the modeling was obtained for review in this study. That LOMR only calculated the 1% annual chance flood discharge and that information is listed below. July 2011 11
Table 4. Comparison of HEC-HMS Discharges to Previously Calculated Discharges Flooding Source and Location Brushy Creek Upstream of Byron Hot Springs Frisk Creek At the Southern Pacific Railway Kellogg Creek At the Southern Pacific Railway 10% Annual Chance Flood HEC HMS Peak Discharges (cfs) 2% Annual Chance Flood 1% Annual Chance Flood 0.2% Annual Chance Flood Location 1,447 3,195 4,017 6,147 At the Southern Pacific Railway 593 1,378 1,741 2,661 At the Southern Pacific Railway 1,097 2,474 3,108 4,736 At the Southern Pacific Railway 10% Annual Chance Flood Previously Calculated Peak Discharges (cfs) 2% Annual Chance Flood 1% Annual Chance Flood 0.2% Annual Chance Flood 1,480 2,580 2,950 N/A 660 1,170 1,310 N/A N/A N/A 1,609 N/A Marsh Creek At Balfour Road 919 1,366 1,568 2,117 At Balfour Road 890 1,900 2,500 5,100 At Union Pacific Railroad At Santa Fe Railroad 1,721 2,751 3,679 6,204 At Union Pacific Railroad 2,476 4,215 5,029 7,209 At Santa Fe Railroad *the effective FIS notes that the 2, 1, and 0.2% annual chance flows are reduced due to overbank spills and non returning flows 2,100 4,200 5,200 8,300 2,300 4,000* 4,000* 4,000* July 2011 12
Since the 1% annual chance flows for Kellogg Creek have increased significantly from the values calculated in the 2002 LOMR, the inputs for the LOMR HEC 1 model were compared to the inputs to the HEC HMS model to determine potential explanations. The first difference between the two models was the precipitation values used. The HEC 1 model used different precipitation values for different subbasins, starting with 4.8 inches in the headwater subbasin and ending with 3.4 inches at the outlet. The HEC HMS model used a constant precipitation value of 4.53 inches for all subbasins. Additionally, the subbasins in the HEC 1 model used the SCS s curve number and unit hydrograph methods while the HEC HMS model used the methods recommended by Contra Costa County (the soil moisture accounting method and the County derived S Curve). This has resulted in large differences in flows from subbasins of similar size. Table 5 below shows some comparisons between subbasin size and calculated flow rate. These differences appear to explain the change in flows between the LOMR HEC 1 and HEC HMS models. Table 5. Comparisons of 1% Annual Chance Flows at Kellogg Creek Subbasins between HEC 1 and HEC HMS Subbasin Number HEC 1 Subbasin Size (sq miles) Flow (cfs) Subbasin Number HEC HMS Subbasin Size (sq miles) Flow (cfs) 2007 0.82 56 5 0.821 396.4 2005 1.32 107 7 1.427 361.1 2004 0.92 128 9 0.999 656.7 The currently effective FIS for Marsh Creek lists flows at 3 locations and those values are also listed in Table 4. The effective flows were calculated using the unit hydrograph method where flood hydrographs were developed for the upper reaches of Marsh Creek, routed through the Marsh Creek flood control reservoir and then summed with hydrographs developed for lower reaches. For the 10% annual chance event the newly calculated flows are comparable to the effective flows. For the 2% annual chance event the flows at Balfour Road have been reduced by about 30%. This is likely due to the five detention ponds and the Marsh Creek Reservoir that store approximately 1,893 acrefeet during the 2% annual chance event. Additionally, as discussed above for Kellogg Creek, the rainfall data has been updated which could result in changes to the flow rates. Similarly, at the Union Pacific Railroad the 2% annual chance flows have been reduced by about 35%. This is likely due to additional detention ponds storing approximately 453 acre feet during the 2% annual chance event. For the 1% annual chance event the flows have been reduced by 48 and 39%, respectively, at Balfour Road and the Union Pacific Railroad. For the 0.2% annual chance event the flows have been reduced by 59 and 25%, respectively, at Balfour Road and the Union Pacific Railroad due to detention pond storage. At the Santa Fe Railroad the effective discharges have been reduced due to overbank spills and non returning flows. Since the new modeling accounts for overbanks spills and nonreturning flows have been removed, the new flows calculated cannot be compared to the effective flows for the 2% annual chance event. July 2011 13
References 1. Contra Costa County Flood Control and Water Conservation District. Verification of the District s Standards. Draft December 2010. 2. Personal Communication (phone call). Contra Costa Water District (Mark Seedall). April 19, 2011. 3. Contra Costa County Flood Control and Water Conservation District. Marsh Creek Hydrology Report GeoHMS and HEC HMS Analysis. May 10, 2010. (and accompanying HEC HMS model) July 2011 14
Appendix A 1 Landuse and Infiltration Rate Calculations July 2011 15
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Table A1 1. Brushy Creek Landuse Area (square miles) by Subbasin Subbasin Agricultural Land Delta Recreation Open Space Parks and Public/Semi Public Water Watershed* Number Recreation 1 1.30 0.08 2 2.44 3 1.21 0.57 4 1.42 5 2.07 0.29 0.28 6 0.57 0.22 7 0.45 0.11 8 1.48 9 0.15 10 0.99 0.05 0.23 0.07 11 0.25 12 0.23 0.27 13 1.46 0.14 0.04 * watershed is a landuse type, not the total for the subbasin Table A1 2. Brushy Creek Landuse Fractions by Subbasin Subbasin Agricultural Land Delta Recreation Open Space Parks and Public/Semi Water Watershed Number Recreation Public 1 0.94 0.06 2 1.00 3 0.68 0.32 4 1.00 5 0.78 0.11 0.11 6 0.72 0.28 7 0.80 0.20 8 1.00 9 1.00 10 0.74 0.04 0.17 0.05 11 1.00 12 0.45 0.01 0.54 13 0.89 0.08 0.02 July 2011 17
Table A1 3. Brushy Creek Area Weighted Infiltration Rate by Subbasin/Landuse Subbasin Agricultural Delta Open Space Parks and Public/Semi Water Watershed Total Number Land Recreation Recreation Public Average 0.175 0.175 0.175 0.175 0.175 0.175 0.175 Infiltration Rate (in/hr) 1 0.165 0.010 0.175 2 0.119 0.056 0.175 3 0.175 0.175 4 0.137 0.019 0.019 0.175 5 0.126 0.049 0.175 6 0.141 0.034 0.175 7 0.175 0.175 8 0.175 0.175 9 0.129 0.006 0.031 0.009 0.175 10 0.175 0.175 11 0.079 0.002 0.095 0.175 12 0.156 0.014 0.004 0.175 13 0.165 0.010 0.175 Please note that the landuse coverage ends at the Alameda/Contra Costa County border. Aerial photos were reviewed to determine if the area of the watershed in Alameda County was being used differently than in Contra Costa County. There did not appear to be a difference in landuse between the two counties so the Contra Costa landuse was applied to the subbasins that fall either partly or entirely in Alameda County. July 2011 18
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Table A1 4. Frisk Creek Landuse Area (square miles) by Subbasin Subbasin Number Agricultural Core Land Agricultural Land Commercial Light Industry Multiple Family Residential Low Multiple Family Residential Medium Open Space 1 0.886 2 0.673 3 1.758 4 1.082 5 0.149 1.475 6 0.480 0.163 7 0.035 0.875 0.013 0.006 0.002 8 0.845 9 0.977 10 0.106 0.295 0.010 0.005 0.015 11 0.099 0.613 0.002 0.051 Subbasin Number Parks and Recreation Public/Semi Public Single Family Residential High Single Family Residential Medium Single Family Residential Very Low Water Watershed 1 0.997 2 0.078 3 0.017 4 0.094 5 0.001 0.001 0.012 6 0.004 7 0.012 0.050 0.070 0.045 8 0.008 9 0.035 0.021 10 0.013 0.049 0.008 11 0.030 0.002 0.001 July 2011 20
Table A1 5. Brushy Creek Landuse Fractions by Subbasin Subbasin Number Agricultural Core Land Agricultural Land Commercial Light Industry Multiple Family Residential Low Multiple Family Residential Medium Open Space 1 0.471 2 0.896 3 0.991 4 0.920 5 0.091 0.900 6 0.742 0.252 7 0.032 0.790 0.012 0.006 0.002 8 0.991 9 0.946 10 0.212 0.590 0.020 0.009 0.030 11 0.124 0.768 0.002 0.064 Subbasin Number Parks and Recreation Public/Semi Public Single Family Residential High Single Family Residential Medium Single Family Residential Very Low Water Watershed 1 0.529 2 0.104 3 0.009 4 0.080 5 0.001 0.001 0.007 6 0.006 7 0.011 0.045 0.063 0.040 8 0.009 9 0.034 0.021 10 0.026 0.097 0.016 11 0.037 0.003 0.002 July 2011 21
Subbasin Number Agricultural Core Land Table A1 6. Frisk Creek Area Weighted Infiltration Rate by Subbasin/Landuse Agricultural Land Commercial Light Industry Multiple Family Residential Low Multiple Family Residential Medium Open Space Parks and Recreation Average 0.175 0.175 0.025 0.035 0.058 0.055 0.175 0.175 Infiltration Rate (in/hr) 1 0.082 2 0.157 3 0.173 4 0.161 5 0.016 0.157 6 0.130 0.044 7 0.006 0.138 8 0.173 9 0.165 10 0.037 0.103 0.001 0.002 11 0.022 0.134 0.011 July 2011 22
Subbasin Number Table A1 6. Frisk Creek Area Weighted Infiltration Rate by Subbasin/Landuse (cont.) Public/Semi Public Single Family Residential High Single Family Residential Medium Single Family Residential Very Low Water Watershed Total Average 0.175 0.066 0.087 0.155 0.175 0.175 Infiltration Rate (in/hr) 1 0.093 0.175 2 0.018 0.175 3 0.002 0.175 4 0.014 0.175 5 0.001 0.175 6 0.001 0.175 7 0.002 0.003 0.005 0.006 0.161 8 0.002 0.175 9 0.006 0.001 0.173 10 0.004 0.006 0.001 0.155 11 0.007 0.174 July 2011 23
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Table A1 7. Kellogg Creek Landuse Area (square miles) by Subbasin Subbasin Number Agricultural Core Agricultural Land Commercial Light Industry Multiple Family Office Park Open Space Land Residential Low 2 3 4 0.20 5 6 7.01 7 382.63 8 138.26 94.76 9 448.35 466.18 10 535.97 11 420.02 0.03 12 353.97 0.06 13 10.82 98.34 8.87 2.40 1.88 0.04 19.69 14 Subbasin Number Parks and Recreation Public/Semi Public Single Family Single Family Water Watershed Residential High Residential Medium 2 6.55 683.11 3 8.71 543.21 4 415.27 5 525.26 6 43.86 1572.47 7 906.06 8 529.51 27.58 112.93 9 354.85 51.20 10 0.28 11 7.00 12 3.71 13 36.37 14 1.04 10.08 0.04 July 2011 25
Table A1 8. Kellogg Creek Landuse Fractions by Subbasin Subbasin Number Agricultural Core Agricultural Land Commercial Light Industry Multiple Family Office Park Open Space Land Residential Low 2 3 4 5 6 7 0.008 8 0.363 9 0.216 0.148 10 0.490 0.510 11 0.987 12 0.991 13 0.907 14 0.071 0.642 0.058 0.016 0.012 0.129 Subbasin Number Parks and Recreation Public/Semi Public Single Family Single Family Water Watershed Residential High Residential Medium 2 0.009 0.991 3 0.016 0.984 4 1.000 5 1.000 6 0.027 0.973 7 0.992 8 0.503 0.026 0.107 9 0.555 0.080 10 11 0.013 12 0.009 13 0.093 14 0.007 0.066 July 2011 26
Subbasin Number Agricultural Core Land Table A1 9. Kellogg Creek Area Weighted Infiltration Rate by Subbasin/Landuse Agricultural Land Commercial Light Industry Multiple Family Residential Low Office Park Open Space Parks and Recreation Average 0.175 0.175 0.025 0.035 0.058 0.025 0.175 0.175 Infiltration Rate (in/hr) 2 0.002 3 4 5 6 0.005 7 0.001 8 0.064 0.088 9 0.038 0.026 0.097 10 0.086 0.089 11 0.173 12 0.173 13 0.159 14 0.012 0.112 0.001 0.001 0.001 0.022 July 2011 27
Subbasin Number Table A1 9. Kellogg Creek Area Weighted Infiltration Rate by Subbasin/Landuse (cont.) Public/Semi Public Single Family Residential High Single Family Residential Medium Water Watershed Total Average 0.175 0.066 0.087 0.175 0.175 Infiltration Rate (in/hr) 2 0.173 0.175 3 0.003 0.172 0.175 4 0.175 0.175 5 0.175 0.175 6 0.170 0.175 7 0.174 0.175 8 0.005 0.019 0.175 9 0.014 0.175 10 0.175 11 0.002 0.175 12 0.002 0.175 13 0.016 0.175 14 0.006 0.156 July 2011 28
July 2011 29
Table A1 10. Mt. Diablo Creek Landuse Area (square miles) by Subbasin Subbasin Number Agricultural Land Commercial Heavy Industry Landfill Light Industry Multiple Family Residential Low Multiple Family Residential Medium Office Park 1 6.816 0.153 0.007 0.055 0.166 0.131 0.003 2 3 0.000 0.112 4 5 0.024 0.094 6 0.177 7 0.088 8 9 0.594 0.542 0.002 10 11 12 Subbasin Number Open Space Parks and Recreation Public/Semi Public Single Family Residential High Single Family Residential Low Single Family Residential Medium Single Family Residential Very Low 1 1.949 7.962 0.603 3.625 0.053 0.310 2 0.063 0.000 0.000 3 1.068 0.004 4 0.131 5 0.882 6 0.003 3.531 0.002 7 0.511 0.075 8 0.335 0.028 9 0.116 0.249 0.808 0.176 10 0.003 0.072 11 0.000 1.111 12 0.024 0.002 July 2011 30
Table A1 11. Mt. Diablo Creek Landuse Fractions by Subbasin Subbasin Number Agricultural Land Commercial Heavy Industry Landfill Light Industry Multiple Family Residential Low Multiple Family Residential Medium 1 0.312 0.007 0.003 0.008 0.006 2 3 0.095 4 5 0.024 0.094 6 0.048 7 0.130 8 9 0.239 0.218 0.001 10 11 12 Office Park Subbasin Number Open Space Parks and Recreation Public/Semi Public Single Family Residential High Single Family Residential Low Single Family Residential Medium Single Family Residential Very Low 1 0.089 0.365 0.028 0.166 0.002 0.014 2 0.991 0.007 0.002 3 0.902 0.003 4 1.000 5 0.882 6 0.001 0.951 0.001 7 0.758 0.112 8 0.924 0.076 9 0.047 0.100 0.325 0.071 10 0.039 0.961 11 1.000 12 0.930 0.070 July 2011 31
Subbasin Number Agricultural Land Table A1 12. Mt. Diablo Creek Area Weighted Infiltration Rate by Subbasin/Landuse Commercial Heavy Industry Landfill Light Industry Multiple Family Residential Low Multiple Family Residential Medium Office Park Average 0.175 0.025 0.040 0.175 0.035 0.058 0.055 0.025 Infiltration Rate (in/hr) 1 0.055 2 3 0.017 4 5 0.004 0.016 6 0.008 7 0.005 8 9 0.042 0.008 10 11 12 July 2011 32
Subbasin Number Table A1 12. Mt. Diablo Creek Area Weighted Infiltration Rate by Subbasin/Landuse (cont.) Open Space Parks and Recreation Public/Semi Public Single Family Residential High Single Family Residential Low Single Family Residential Medium Single Family Residential Very Low Average 0.175 0.175 0.175 0.066 0.123 0.087 0.155 Infiltration Rate (in/hr) 1 0.016 0.064 0.005 0.011 0.002 0.154 2 0.173 0.174 3 0.158 0.175 4 0.175 0.175 5 0.154 0.175 6 0.166 0.175 7 0.133 0.020 0.157 8 0.162 0.013 0.175 9 0.008 0.018 0.057 0.005 0.137 10 0.007 0.168 0.175 11 0.175 0.175 12 0.163 0.012 0.175 Total July 2011 33
Table A1 13 Marsh Creek Original and Revised Landuse Areas (square miles) by Subbasin Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Agricultural Agricultural Business Commercial Agricultural Agricultural Business Commercial Core Land Land Park Core Land Land Park 104 3 2.693 2.693 104 DSFairview 104 DSSpaL 104 LowBasin 0.922 0.092 1.237 0.157 104 SpaL 104 UpBasin 1.162 1.682 105 BtwdLk12 0.004 0.004 105 BtwdLk14 105 BtwdLk18 0.014 0.005 0.014 0.005 105 BtwdLk5 0.000 105 DeeratMC 105 DeerBasin 0.003 105 DeerDam 3.014 105 DSBtwdLk14 105 DSBtwdLk18 0.000 0.000 105 DSBtwdLk5 105 DSDeerBasin 105 DSDeerDam 0.360 0.008 0.360 0.008 106 DryBasin 0.005 0.049 0.005 0.010 106 DryDam 1.845 1.845 107 7940Basin 0.143 0.025 107 8085Basin 0.000 0.000 107 DS8085Basin 0.000 0.017 0.000 0.010 107 DSVYNorthSM 0.000 0.000 0.000 107 DSVYSouthSM 0.000 0.000 107 VYNorth 0.341 0.299 107 VYSouth 0.318 0.318 108 EofMCDam 108 MCDam 27.645 27.645 30A 2 30A BrownBas 30A LaurelBas 0.048 0.100 30C DSFVBasin 0.138 30C DSLibertyBas 0.017 0.077 0.017 30C FairviewBas 0.147 0.181 0.026 0.001 0.181 30C LibertyBas 0.094 0.015 0.027 0.015 52A 1 0.000 52A 2 52B 1 0.118 0.118 52C Basin1 0.003 0.075 0.003 0.061 0.086 52C Basin2 0.020 0.003 0.007 0.003 52C Basin3 0.003 0.031 0.003 0.026 52C Lowest 0.001 0.001 0.001 0.001 0.063 52D Outlet 0.142 0.142 MC 118.5 0.043 MC 137.0 0.002 0.002 MC 139.0 MC 160.0 0.001 0.001 MC 184.0 0.001 0.036 0.001 0.036 MC 198.0 0.128 0.011 0.128 0.011 MC 217.5 0.059 0.059 MC 236.5 0.029 0.036 0.029 0.036 MC 252.0 0.002 0.014 0.002 0.014 MC 254.0 0.002 MC 259.0 0.011 0.011 July 2011 34
Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Agricultural Agricultural Business Commercial Agricultural Agricultural Business Commercial Core Land Land Park Core Land Land Park MC 263.0 0.008 0.008 MC 287.0 0.000 0.000 MC 305.5 0.064 0.064 MC 312.0 0.000 0.016 MC 312.5 0.077 0.077 MC 331.1 MC 338.5 MC 363.6 MC 372.0 MC 379.5 MC 380.5 MC 386.0 MC 387.0 MC 389.0 MC 393.4 MC 401.0 0.011 0.003 0.011 0.003 MC 404.2 0.003 0.003 MC 404.7 MC at30alaruelout 0.040 0.073 0.040 MC at30coutlet 0.012 0.000 0.012 MC at52c 0.000 0.000 MC at52d Outlet MC at52d OutletSM MC at8085basin 0.036 0.067 0.036 0.065 MC atds7940basin 0.135 0.015 0.135 MCatDS7940BasSM 0.001 MC atvynorth 0.040 0.009 0.040 0.009 MC atvysouth 0.001 0.001 MC DSECCID 0.000 0.000 0.000 0.000 MC ECCID 0.418 0.012 0.418 0.007 MC Outlet3 0.011 0.011 MC US30ALaruelOut 0.000 0.000 Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Light MultiFamily MultiFamily Mobile Light MultiFamily MultiFamily Mobile Industry Low Medium Homes Industry Low Medium Homes 104 3 104 DSFairview 104 DSSpaL 104 LowBasin 0.056 0.053 0.001 104 SpaL 104 UpBasin 105 BtwdLk12 105 BtwdLk14 105 BtwdLk18 105 BtwdLk5 105 DeeratMC 0.050 105 DeerBasin 0.001 0.012 0.022 105 DeerDam 105 DSBtwdLk14 105 DSBtwdLk18 0.004 0.004 105 DSBtwdLk5 105 DSDeerBasin 105 DSDeerDam 0.007 0.000 0.006 0.000 106 DryBasin 0.018 July 2011 35
Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Light MultiFamily MultiFamily Mobile Light MultiFamily MultiFamily Mobile Industry Low Medium Homes Industry Low Medium Homes 106 DryDam 107 7940Basin 107 8085Basin 107 DS8085Basin 107 DSVYNorthSM 107 DSVYSouthSM 107 VYNorth 107 VYSouth 108 EofMCDam 108 MCDam 30A 2 0.001 30A BrownBas 30A LaurelBas 0.010 30C DSFVBasin 0.000 30C DSLibertyBas 0.006 30C FairviewBas 0.099 0.003 0.023 30C LibertyBas 52A 1 0.078 0.024 0.000 0.009 0.078 0.024 0.009 52A 2 0.012 0.005 0.012 52B 1 0.018 0.046 0.021 0.018 0.021 52C Basin1 0.131 0.014 0.014 0.046 0.131 0.003 0.014 0.046 52C Basin2 0.000 0.038 0.038 52C Basin3 0.174 0.005 0.005 52C Lowest 52D Outlet 0.213 MC 118.5 0.000 MC 137.0 0.000 MC 139.0 0.000 MC 160.0 0.000 MC 184.0 MC 198.0 MC 217.5 MC 236.5 MC 252.0 0.012 MC 254.0 0.020 MC 259.0 0.016 MC 263.0 0.002 MC 287.0 0.000 MC 305.5 MC 312.0 MC 312.5 0.000 0.000 0.000 0.000 MC 331.1 0.000 0.000 MC 338.5 0.000 0.000 MC 363.6 0.007 MC 372.0 0.002 MC 379.5 MC 380.5 MC 386.0 MC 387.0 MC 389.0 MC 393.4 MC 401.0 0.035 0.000 MC 404.2 MC 404.7 MCat30ALaruelOut 0.095 MC at30coutlet 0.024 MC at52c July 2011 36
Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Light MultiFamily MultiFamily Mobile Light MultiFamily MultiFamily Mobile Industry Low Medium Homes Industry Low Medium Homes MC at52d Outlet 0.000 MC at52d OutletSM 0.000 MC at8085basin MC atds7940basin MCatDS7940BasSM MC atvynorth MC atvysouth MC DSECCID MC ECCID MC Outlet3 0.000 0.004 0.000 MC US30ALaruelOut 0.000 Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin MultiUse MultiFamily Office Open Space MultiUse MultiFamily Office Open Space Very High Very High 104 3 0.388 0.565 104 DSFairview 0.004 0.077 104 DSSpaL 104 LowBasin 0.296 0.909 104 SpaL 0.003 0.003 104 UpBasin 0.849 1.487 105 BtwdLk12 0.013 0.013 105 BtwdLk14 105 BtwdLk18 0.025 0.025 105 BtwdLk5 0.001 0.001 105 DeeratMC 0.002 0.002 105 DeerBasin 0.020 0.020 105 DeerDam 0.945 0.945 105 DSBtwdLk14 105 DSBtwdLk18 0.000 0.000 105 DSBtwdLk5 105 DSDeerBasin 0.012 0.012 105 DSDeerDam 0.022 0.022 106 DryBasin 0.044 0.074 106 DryDam 0.085 0.085 107 7940Basin 0.017 0.017 107 8085Basin 0.006 0.006 107 DS8085Basin 0.014 0.014 107 DSVYNorthSM 107 DSVYSouthSM 107 VYNorth 0.000 0.000 107 VYSouth 108 EofMCDam 108 MCDam 1.651 1.651 30A 2 0.003 0.003 30A BrownBas 0.034 0.034 30A LaurelBas 30C DSFVBasin 30C DSLibertyBas 30C FairviewBas 0.133 0.003 0.138 0.003 30C LibertyBas 52A 1 0.003 0.000 0.003 0.000 52A 2 0.000 0.000 52B 1 0.051 0.000 0.022 0.000 0.058 0.022 0.000 52C Basin1 0.027 0.005 0.053 0.027 0.115 July 2011 37
Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin MultiUse MultiFamily Office Open Space MultiUse MultiFamily Office Open Space Very High Very High 52C Basin2 0.062 0.000 0.001 0.062 0.007 52C Basin3 0.050 0.398 52C Lowest 52D Outlet 0.009 MC 118.5 MC 137.0 MC 139.0 MC 160.0 MC 184.0 MC 198.0 MC 217.5 MC 236.5 MC 252.0 MC 254.0 MC 259.0 MC 263.0 MC 287.0 MC 305.5 0.001 0.001 MC 312.0 MC 312.5 MC 331.1 MC 338.5 MC 363.6 0.000 0.000 MC 372.0 MC 379.5 MC 380.5 MC 386.0 MC 387.0 MC 389.0 MC 393.4 MC 401.0 0.034 0.015 0.034 0.015 MC 404.2 0.000 0.000 MC 404.7 MCat30ALaruelOut MC at30coutlet 0.003 0.003 MC at52c MC at52d Outlet MC at52d OutletSM MC at8085basin MC atds7940basin MCatDS7940BasSM MC atvynorth MC atvysouth MC DSECCID 0.002 0.002 MC ECCID MC Outlet3 MC US30ALaruelOut Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Parks Public Semi Single Single Parks Public Semi Single Single Recreation Public Family High Family Low Recreation Public Family High Family Low 104 3 2.129 0.051 2.129 104 DSFairview 0.007 0.040 0.024 0.067 0.007 0.040 0.414 104 DSSpaL 0.000 0.000 0.000 July 2011 38
Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Parks Public Semi Single Single Parks Public Semi Single Single Recreation Public Family High Family Low Recreation Public Family High Family Low 104 LowBasin 0.008 0.169 0.762 0.141 0.169 0.385 104 SpaL 0.017 0.005 0.000 0.017 0.005 0.592 104 UpBasin 0.741 0.259 1.304 0.039 1.323 0.268 0.865 105 BtwdLk12 0.101 0.144 0.101 0.144 105 BtwdLk14 0.027 0.022 0.026 0.024 105 BtwdLk18 0.074 0.030 0.074 0.030 105 BtwdLk5 0.036 0.005 0.021 0.036 0.005 0.022 105 DeeratMC 0.001 0.014 0.008 0.001 0.014 0.227 105 DeerBasin 0.102 0.117 0.093 0.175 0.072 0.117 0.387 0.018 105 DeerDam 0.021 0.018 0.021 0.018 105 DSBtwdLk14 0.076 0.000 0.040 0.017 0.000 0.098 0.000 105 DSBtwdLk18 0.008 0.001 0.008 0.001 105 DSBtwdLk5 0.014 0.039 0.014 0.039 105 DSDeerBasin 0.003 0.001 0.034 0.060 0.003 0.001 0.099 105 DSDeerDam 0.087 0.180 0.131 0.087 0.181 0.131 106 DryBasin 0.139 0.124 0.062 0.010 0.139 0.122 0.314 106 DryDam 0.716 0.036 0.146 0.716 0.036 0.196 107 7940Basin 0.028 0.062 0.008 0.028 0.062 0.237 107 8085Basin 0.016 0.062 0.016 0.063 107 DS8085Basin 0.013 0.034 0.013 0.042 107 DSVYNorthSM 0.001 0.001 0.000 107 DSVYSouthSM 107 VYNorth 0.340 0.058 0.340 0.058 0.042 107 VYSouth 0.060 0.000 0.060 0.000 108 EofMCDam 0.486 0.486 108 MCDam 20.013 0.247 20.013 0.247 0.000 30A 2 0.002 0.000 0.002 0.016 30A BrownBas 0.037 0.007 0.057 0.038 0.219 0.055 30A LaurelBas 0.008 0.046 0.244 0.106 0.039 0.046 0.281 0.187 30C DSFVBasin 0.025 0.000 0.057 0.133 0.000 30C DSLibertyBas 0.000 0.435 0.011 0.265 0.283 30C FairviewBas 0.102 0.000 0.252 0.107 0.147 30C LibertyBas 0.116 0.350 0.168 0.391 0.181 52A 1 0.004 0.025 0.073 0.025 0.282 52A 2 0.003 0.009 0.034 0.003 0.122 52B 1 0.007 0.030 0.000 0.007 0.030 0.074 0.000 52C Basin1 0.001 0.073 0.001 0.073 0.567 52C Basin2 0.004 0.096 0.083 0.004 0.096 0.183 52C Basin3 0.000 0.009 0.266 0.000 0.009 0.174 52C Lowest 0.046 0.110 0.063 0.046 0.110 52D Outlet 0.003 0.014 0.003 0.014 0.203 MC 118.5 0.001 0.158 0.001 0.165 0.001 MC 137.0 0.012 0.010 0.265 0.007 0.012 0.010 0.201 0.017 MC 139.0 0.008 0.022 0.008 0.024 MC 160.0 0.010 0.084 0.010 0.169 MC 184.0 0.005 0.163 0.172 0.005 0.001 0.172 MC 198.0 0.009 0.024 0.034 0.009 0.128 MC 217.5 0.002 0.002 MC 236.5 0.006 0.000 0.088 0.006 0.019 0.098 MC 252.0 0.001 0.000 0.001 0.012 MC 254.0 0.002 0.002 0.002 0.020 MC 259.0 0.002 0.002 0.016 MC 263.0 0.009 0.009 0.002 MC 287.0 0.007 0.106 0.007 0.000 0.106 MC 305.5 0.003 0.000 0.003 0.000 0.000 MC 312.0 0.020 0.233 0.020 0.071 0.149 MC 312.5 0.016 0.053 0.016 0.011 0.044 MC 331.1 0.003 0.003 0.000 July 2011 39
Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Parks Public Semi Single Single Parks Public Semi Single Single Recreation Public Family High Family Low Recreation Public Family High Family Low MC 338.5 0.004 0.004 0.000 MC 363.6 0.003 0.003 0.007 MC 372.0 0.002 0.002 0.162 MC 379.5 0.000 0.000 0.016 MC 380.5 0.002 0.002 0.009 MC 386.0 0.000 0.000 0.000 0.019 MC 387.0 0.001 0.001 0.023 MC 389.0 0.002 0.002 0.007 MC 393.4 0.003 0.000 0.003 0.045 MC 401.0 0.097 0.094 0.079 0.023 0.097 0.129 0.239 MC 404.2 0.008 0.000 0.008 0.143 MC 404.7 0.003 0.003 0.065 MCat30ALaruelOut 0.006 0.008 0.008 0.006 0.213 0.016 MC at30coutlet 0.005 0.005 0.024 MC at52c 0.007 0.007 MC at52d Outlet 0.007 0.007 0.000 MC at52d OutletSM 0.000 0.000 0.000 MC at8085basin 0.000 0.000 0.002 MC atds7940basin 0.000 0.000 0.015 MCatDS7940BasSM 0.001 MC atvynorth 0.007 0.022 0.007 0.022 MC atvysouth 0.051 0.051 MC DSECCID 0.002 0.010 0.002 0.010 0.001 MC ECCID 0.012 0.011 0.012 0.016 MC Outlet3 0.009 0.009 0.004 MC US30ALaruelOut 0.006 0.006 0.000 Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Single Family Single Family Watershed Single Family Single Family Watershed Medium Very Low Medium Very Low 104 3 0.125 104 DSFairview 0.397 0.056 0.056 104 DSSpaL 0.000 104 LowBasin 0.646 0.006 104 SpaL 0.592 0.000 0.000 104 UpBasin 1.270 105 BtwdLk12 105 BtwdLk14 0.000 105 BtwdLk18 105 BtwdLk5 0.000 105 DeeratMC 0.169 0.002 0.002 105 DeerBasin 0.127 105 DeerDam 105 DSBtwdLk14 0.000 105 DSBtwdLk18 105 DSBtwdLk5 105 DSDeerBasin 0.005 0.000 0.000 105 DSDeerDam 106 DryBasin 0.214 106 DryDam 0.050 107 7940Basin 0.111 107 8085Basin 0.000 107 DS8085Basin 0.000 107 DSVYNorthSM July 2011 40
Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Single Family Single Family Watershed Single Family Single Family Watershed Medium Very Low Medium Very Low 107 DSVYSouthSM 107 VYNorth 0.000 107 VYSouth 108 EofMCDam 0.028 0.028 108 MCDam 0.311 1.164 0.311 1.164 30A 2 0.015 30A BrownBas 0.286 0.074 30A LaurelBas 0.351 0.161 30C DSFVBasin 0.165 0.139 0.000 30C DSLibertyBas 0.119 0.221 0.072 0.075 30C FairviewBas 0.244 0.059 0.079 0.015 30C LibertyBas 0.018 0.274 0.018 0.067 52A 1 0.351 52A 2 0.142 52B 1 0.035 0.000 52C Basin1 0.685 52C Basin2 0.093 52C Basin3 0.077 52C Lowest 52D Outlet MC 118.5 0.051 0.061 0.061 MC 137.0 0.003 0.058 MC 139.0 0.002 MC 160.0 0.092 0.020 0.027 MC 184.0 0.000 0.064 0.226 MC 198.0 0.093 0.053 0.078 MC 217.5 MC 236.5 0.057 0.001 0.029 MC 252.0 0.000 0.024 0.024 MC 254.0 MC 259.0 MC 263.0 MC 287.0 0.015 0.015 MC 305.5 0.000 MC 312.0 0.005 0.002 MC 312.5 0.002 MC 331.1 0.000 0.005 0.005 MC 338.5 0.000 0.056 0.056 MC 363.6 0.000 MC 372.0 0.159 MC 379.5 0.016 MC 380.5 0.009 MC 386.0 0.019 MC 387.0 0.023 MC 389.0 0.007 MC 393.4 0.045 MC 401.0 0.138 MC 404.2 0.144 MC 404.7 0.065 MC at30alaruelout 0.207 MC at30coutlet 0.000 0.000 MC at52c MC at52d Outlet 0.000 0.000 0.000 MC at52d OutletSM MC at8085basin MC atds7940basin MC atds7940bassm MC atvynorth July 2011 41
Original Landuse (sq miles) Revised Landuse (sq miles) Subbasin Single Family Single Family Watershed Single Family Single Family Watershed Medium Very Low Medium Very Low MC atvysouth MC DSECCID 0.001 MC ECCID MC Outlet3 MC US30ALaruelOut Subbasin Table A1 14. Marsh Creek Original versus Revised Infiltration Rates by Subbasin Original Infiltration Rate (in/hr) Revised Infiltration Rate (in/hr) Subbasin Original Infiltration Rate (in/hr) Revised Infiltration Rate (in/hr) 104 3 0.175 0.170 108 MCDam 0.175 0.173 104 DSFairview 0.091 0.089 30A 2 0.093 0.096 104 DSSpaL 0.155 0.066 30A BrownBas 0.084 0.084 104 LowBasin 0.153 0.113 30A LaurelBas 0.108 0.081 104 SpaL 0.070 0.090 30C DSFVBasin 0.131 0.114 104 UpBasin 0.158 0.126 30C DSLibertyBas 0.107 0.124 105 BtwdLk12 0.115 0.114 30C FairviewBas 0.095 0.056 105 BtwdLk14 0.123 0.123 30C LibertyBas 0.105 0.123 105 BtwdLk18 0.148 0.132 52A 1 0.083 0.075 105 BtwdLk5 0.138 0.126 52A 2 0.087 0.080 105 DeeratMC 0.073 0.083 52B 1 0.052 0.040 105 DeerBasin 0.104 0.110 52C Basin1 0.084 0.077 105 DeerDam 0.175 0.176 52C Basin2 0.086 0.073 105 DSBtwdLk14 0.082 0.134 52C Basin3 0.136 0.063 105 DSBtwdLk18 0.130 0.128 52C Lowest 0.132 0.063 105 DSBtwdLk5 0.095 0.095 52D Outlet 0.115 0.103 105 DSDeerBasin 0.081 0.108 MC 118.5 0.089 0.090 105 DSDeerDam 0.155 0.146 MC 137.0 0.081 0.075 106 DryBasin 0.121 0.103 MC 139.0 0.093 0.066 106 DryDam 0.168 0.167 MC 160.0 0.075 0.084 107 7940Basin 0.105 0.075 MC 184.0 0.097 0.097 107 8085Basin 0.094 0.115 MC 198.0 0.132 0.129 107 DS8085Basin 0.116 0.105 MC 217.5 0.175 0.172 107 DSVYNorthSM 0.151 0.167 MC 236.5 0.105 0.102 107 DSVYSouthSM 0.175 0.040 MC 252.0 0.072 0.098 107 VYNorth 0.169 0.101 MC 254.0 0.073 0.059 107 VYSouth 0.175 0.061 MC 259.0 0.059 0.044 108 EofMCDam 0.175 0.171 MC 263.0 0.103 0.043 July 2011 42
Table A1 14. Marsh Creek Original versus Revised Infiltration Rates by Subbasin (cont). Subbasin Original Infiltration Rate (in/hr) Revised Infiltration Rate (in/hr) MC 287.0 0.122 0.115 MC 305.5 0.031 0.022 MC 312.0 0.105 0.117 MC 312.5 0.074 0.062 MC 331.1 0.118 0.121 MC 338.5 0.092 0.149 MC 363.6 0.096 0.059 MC 372.0 0.067 0.086 MC 379.5 0.067 0.087 MC 380.5 0.082 0.083 MC 386.0 0.067 0.087 MC 387.0 0.070 0.086 MC 389.0 0.086 0.082 MC 393.4 0.073 0.085 MC 401.0 0.112 0.089 MC 404.2 0.071 0.087 MC 404.7 0.071 0.086 MC at30alaruelout 0.091 0.071 MC at30coutlet 0.074 0.056 MC at52c 0.175 0.061 MC at52d Outlet 0.171 0.063 MC at52d OutletSM 0.159 0.060 MC at8085basin 0.112 0.087 MC atds7940basin 0.007 0.162 MC atds7940bassm 0.066 0.040 MC atvynorth 0.085 0.140 MC atvysouth 0.175 0.167 MC DSECCID 0.165 0.088 MC ECCID 0.010 0.167 MC Outlet3 0.088 0.043 MC US30ALaruelOut 0.170 0.058 July 2011 43
Appendix A 2 Lag Time Calculations July 2011 44
July 2011 45
Table A2-1. Brushy Creek Area-Weighted Manning s N Calculations Subbasin Agricultural Delta Open Space Parks and Public/Semi Water Watershed Total Number Land Recreation Recreation Public Average 0.085 0.058 0.085 0.075 0.028 0.028 0.085 Manning s n 1 0.080 0.007 0.087 2 0.085 0.085 3 0.058 0.043 0.100 4 0.085 0.085 5 0.067 0.022 0.024 0.112 6 0.061 0.017 0.078 7 0.068 0.008 0.077 8 0.085 0.085 9 0.085 0.085 10 0.063 0.004 0.007 0.006 0.079 11 0.085 0.085 12 0.038 0.008 0.046 13 0.076 0.012 0.001 0.088 July 2011 46
Table A2-2. Brushy Creek Lag Time Calculations Subbasin Number Stream Length (miles) Lca Length (miles) Upstream Elevation (feet) Downstream Elevation (feet) Slope (ft/mile) Manning s n Lag time (hours) 1 2.021 0.622 1356 820 265.155 0.087 0.789 2 3.500 1.342 1292 438 243.990 0.085 1.292 3 3.129 1.491 1214 336 280.623 0.100 1.477 4 2.740 0.914 1026 336 251.852 0.085 1.011 5 4.875 2.379 1198 152 214.552 0.112 2.460 6 2.156 1.163 990 214 360.006 0.078 0.868 7 1.766 0.868 814 214 339.671 0.077 0.718 8 2.604 1.410 792 102 264.958 0.085 1.158 9 0.762 0.375 368 168 262.505 0.085 0.440 10 3.067 1.459 320 44 89.978 0.079 1.425 11 1.158 0.740 168 102 57.000 0.085 0.892 12 3.028 1.980 236 44 63.417 0.046 0.991 13 4.976 3.401 216 4 42.605 0.088 3.033 July 2011 47
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Subbasin Number Agricultural Core Land Table A2 3. Frisk Creek Area Weighted Manning s N Calculations Agricultural Land Commercial Light Industry Multiple Family Residential Low Multiple Family Residential Medium Open Space Parks and Recreation Average 0.075 0.085 0.028 0.053 0.028 0.028 0.085 0.075 Manning s N 1 0.040 2 0.076 3 0.084 4 0.078 5 0.007 0.076 6 0.056 0.021 7 0.002 0.067 8 0.084 9 0.080 10 0.016 0.050 0.001 0.001 0.001 11 0.009 0.065 0.005 July 2011 49
Subbasin Number Public/Semi Public Table A2 3. Frisk Creek Area Weighted Manning s N Calculations (cont.) Single Family Residential High Single Family Residential Medium Single Family Residential Very Low Water Watershed Total Average 0.028 0.028 0.028 0.028 0.028 0.085 Manning s N 1 0.045 0.085 2 0.009 0.085 3 0.001 0.085 4 0.007 0.085 5 0.001 0.084 6 0.077 7 0.001 0.002 0.001 0.075 8 0.084 9 0.001 0.001 0.082 10 0.001 0.003 0.072 11 0.001 0.081 July 2011 50
Table A2-4. Frisk Creek Lag Time Calculations Subbasin Number Stream Length (miles) Lca Length (miles) Upstream Elevation (feet) Downstream Elevation (feet) Slope (ft/mile) Manning s n Lag time (hours) 1 3.315 1.739 922 116 243.113 0.085 1.398 2 1.919 0.911 380 116 137.566 0.085 0.990 3 3.104 1.678 352 56 95.353 0.085 1.607 4 2.419 1.258 236 56 74.412 0.085 1.373 5 3.562 2.366 342 32 87.030 0.084 1.940 6 2.037 0.924 182 32 73.649 0.077 1.038 7 3.002 2.000 94 8 28.651 0.075 1.880 8 1.400 0.368 44 30 9.998 0.084 1.012 9 2.739 1.846 30 8 8.031 0.082 2.452 10 2.071 1.231 32 8 11.590 0.072 1.548 11 2.267 0.776 28 2 11.468 0.081 1.515 July 2011 51
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Subbasin Number Agricultural Core Land Table A2 5. Kellogg Creek Area Weighted Manning s N Calculations Agricultural Land Commercial Light Industry Multiple Family Residential Low Office Park Open Space Parks and Recreation Average 0.075 0.085 0.028 0.053 0.028 0.028 0.085 0.075 Manning s N 2 0.001 3 4 5 6 0.002 7 0.001 8 0.031 0.038 9 0.016 0.013 0.042 10 0.037 0.043 11 0.074 12 0.074 13 0.068 14 0.005 0.055 0.002 0.001 0.011 July 2011 53
Subbasin Number Table A2 5. Kellogg Creek Area Weighted Manning s N Calculations (cont.) Public/Semi Public Single Family Residential High Single Family Residential Medium Water Watershed Total Average 0.028 0.028 0.028 0.028 0.085 Manning s N 2 0.084 0.085 3 0.084 0.084 4 0.085 0.085 5 0.085 0.085 6 0.083 0.085 7 0.084 0.085 8 0.001 0.009 0.078 9 0.002 0.073 10 0.080 11 0.074 12 0.075 13 0.003 0.071 14 0.002 0.076 July 2011 54
Table A2-6. Kellogg Creek Lag Time Calculations Subbasin Number Stream Length (miles) Lca Length (miles) Upstream Elevation (feet) Downstream Elevation (feet) Slope (ft/mile) Manning s n Lag time (hours) 2 2.545 1.337 1178 202 383.508 0.085 1.049 3 1.923 0.797 1258 254 522.185 0.084 0.722 4 2.193 0.791 1171 202 441.851 0.085 0.791 5 2.286 1.344 961 205 330.722 0.085 1.038 6 3.238 1.657 921 136 242.423 0.085 1.361 7 3.642 2.099 693 136 152.957 0.085 1.699 8 2.802 1.011 397 3 140.612 0.078 1.087 9 2.654 1.424 359 3 134.116 0.073 1.145 10 4.161 1.624 181 3 42.781 0.080 1.944 11 2.460 1.347 77 3 30.080 0.074 1.467 12 2.032 1.000 51 3 23.616 0.075 1.292 13 2.051 1.253 45 3 20.473 0.071 1.374 14 1.430 0.832 23 3 13.989 0.076 1.180 July 2011 55
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Subbasin Number Agricultural Land Table A2 7. Mt. Diablo Creek Area Weighted Manning s N by Landuse Commercial Heavy Industry Landfill Light Industry Multiple Family Residential Low Multiple Family Residential Medium Office Park Average 0.085 0.028 0.038 0.035 0.053 0.028 0.028 0.028 Manning s N 1 0.027 2 3 0.003 4 5 0.002 0.003 6 0.004 7 0.007 8 0.002 9 0.020 0.012 10 11 12 July 2011 57
Subbasin Number Open Space Contra Costa County, California Hydrologic Analyses Table A2 7. Mt. Diablo Creek Area Weighted Manning s N by Landuse (cont.) Parks and Recreation Public/Semi Public Single Family Residential High Single Family Residential Low Single Family Residential Medium Single Family Residential Very Low Average 0.085 0.075 0.028 0.028 0.028 0.028 0.028 Manning s N 1 0.008 0.027 0.001 0.005 0.068 2 0.028 0.028 3 0.025 0.029 4 0.028 0.028 5 0.025 0.030 6 0.027 0.031 7 0.064 0.003 0.074 8 0.036 0.005 0.053 9 0.004 0.008 0.009 0.002 0.054 10 0.003 0.027 0.030 11 0.028 0.028 12 0.079 0.002 0.081 Total July 2011 58
Table A2-8. Mt. Diablo Creek Lag Time Calculations Subbasin Number Stream Length (miles) Lca Length (miles) Upstream Elevation (feet) Downstream Elevation (feet) Slope (ft/mile) Manning s n Lag time (hours) 1 11.653 5.872 3800 218 307.388 0.068 2.738 2 0.730 0.409 218 186 43.864 0.028 0.207 3 3.246 1.992 1438 186 385.701 0.029 0.456 4 0.735 0.474 318 168 204.140 0.028 0.164 5 1.966 0.688 1176 168 512.793 0.030 0.247 6 4.048 1.632 168 58 27.174 0.031 0.814 7 2.678 1.060 122 4 44.062 0.074 1.286 8 1.202 0.478 26 4 18.304 0.053 0.593 9 2.275 1.512 58 6 22.854 0.054 1.144 10 0.373 0.222 6 4 5.364 0.030 0.203 11 2.137 1.333 602 2 280.726 0.028 0.343 12 0.513 0.239 4 0 7.792 0.081 0.593 July 2011 59
Table A2 9. Marsh Creek Original and Revised Manning s n and Lag Time by Subbasin Subbasin Original Manning s n Revised Manning s n Original lag time (hrs) Revised lag time (hrs) 104 3 0.0733 0.0810 2.004 2.216 104 DSFairview 0.0253 0.0359 0.243 0.344 104 DSSpaL 0.0240 0.0280 0.007 0.008 104 LowBasin 0.0445 0.0709 1.048 1.672 104 SpaL 0.0253 0.0295 0.519 0.605 104 UpBasin 0.0613 0.0712 1.616 1.877 105 BtwdLk12 0.0437 0.0499 0.395 0.451 105 BtwdLk14 0.0361 0.0525 0.136 0.198 105 BtwdLk18 0.0384 0.0667 0.327 0.568 105 BtwdLk5 0.0574 0.0554 0.242 0.233 105 DeeratMC 0.0250 0.0285 0.269 0.307 105 DeerBasin 0.0265 0.0358 0.349 0.473 105 DeerDam 0.0751 0.0847 2.008 2.264 105 DSBtwdLk14 0.0445 0.0350 0.346 0.272 105 DSBtwdLk18 0.0275 0.0575 0.077 0.161 105 DSBtwdLk5 0.0322 0.0407 0.211 0.267 105 DSDeerBasin 0.0264 0.0351 0.198 0.265 105 DSDeerDam 0.0557 0.0605 0.961 1.045 106 DryBasin 0.0328 0.0446 0.616 0.838 106 DryDam 0.0720 0.0779 1.324 1.432 107 7940Basin 0.0245 0.0380 0.260 0.403 107 8085Basin 0.0268 0.0322 0.119 0.143 107 DS8085Basin 0.0262 0.0453 0.174 0.301 107 DSVYNorthSM 0.0581 0.0743 0.033 0.043 107 DSVYSouthSM 0.0404 0.0850 0.019 0.039 107 VYNorth 0.0624 0.0726 0.820 0.956 107 VYSouth 0.0561 0.0834 0.433 0.643 108 EofMCDam 0.0748 0.0755 0.955 0.964 108 MCDam 0.0748 0.0805 6.160 6.624 30A 2 0.0257 0.0360 0.095 0.133 30A BrownBas 0.0250 0.0280 0.295 0.330 30A LaurelBas 0.0249 0.0372 0.224 0.336 30C DSFVBasin 0.0267 0.0519 0.377 0.732 30C DSLibertyBas 0.0273 0.0335 0.489 0.601 30C FairviewBas 0.0235 0.0297 0.415 0.525 30C LibertyBas 0.0272 0.0280 0.411 0.423 52A 1 0.0245 0.0389 0.497 0.789 52A 2 0.0248 0.0391 0.263 0.414 52B 1 0.0225 0.0303 0.349 0.469 52C Basin1 0.0246 0.0400 0.505 0.819 52C Basin2 0.0251 0.0305 0.307 0.373 July 2011 60
Table A2 9. Marsh Creek Original and Revised Manning s n and Lag Time by Subbasin (cont.) Subbasin Original Manning s n Revised Manning s n Original lag time (hrs) Revised lag time (hrs) 52C Basin3 0.0239 0.0652 0.400 1.090 52C Lowest 0.0239 0.0384 0.296 0.476 52D Outlet 0.0318 0.0516 0.624 1.011 MC 118.5 0.0253 0.0372 0.257 0.377 MC 137.0 0.0245 0.0300 0.345 0.422 MC 139.0 0.0240 0.0280 0.150 0.175 MC 160.0 0.0251 0.0284 0.232 0.262 MC 184.0 0.0258 0.0282 0.359 0.392 MC 198.0 0.0329 0.0487 0.355 0.525 MC 217.5 0.0445 0.0833 0.216 0.405 MC 236.5 0.0280 0.0356 0.344 0.437 MC 252.0 0.0265 0.0306 0.111 0.128 MC 254.0 0.0236 0.0280 0.099 0.117 MC 259.0 0.0228 0.0280 0.090 0.110 MC 263.0 0.0227 0.0280 0.075 0.092 MC 287.0 0.0268 0.0280 0.148 0.155 MC 305.5 0.0215 0.0280 0.121 0.157 MC 312.0 0.0269 0.0280 0.322 0.335 MC 312.5 0.0238 0.0280 0.138 0.163 MC 331.1 0.0271 0.0281 0.100 0.104 MC 338.5 0.0287 0.0280 0.173 0.169 MC 363.6 0.0236 0.0281 0.067 0.079 MC 372.0 0.0252 0.0280 0.248 0.276 MC 379.5 0.0252 0.0280 0.087 0.097 MC 380.5 0.0250 0.0280 0.067 0.076 MC 386.0 0.0252 0.0280 0.096 0.107 MC 387.0 0.0251 0.0280 0.077 0.086 MC 389.0 0.0249 0.0280 0.073 0.081 MC 393.4 0.0251 0.0280 0.101 0.112 MC 401.0 0.0253 0.0382 0.413 0.624 MC 404.2 0.0255 0.0293 0.307 0.352 MC 404.7 0.0251 0.0280 0.177 0.197 MCat30ALaruelOut 0.0243 0.0407 0.209 0.350 MC at30coutlet 0.0234 0.0316 0.121 0.164 MC at52c 0.0538 0.0288 0.185 0.099 MC at52d Outlet 0.0464 0.0280 0.187 0.113 MC at52d OutletSM 0.0237 0.0280 0.005 0.006 MC at8085basin 0.0304 0.0839 0.172 0.476 July 2011 61
Table A2 9. Marsh Creek Original and Revised Manning s n and Lag Time by Subbasin (cont.) Subbasin Original Manning s n Revised Manning s n Original lag time (hrs) Revised lag time (hrs) MCatDS7940Basin 0.0428 0.0794 0.379 0.702 MCatDS7940BasSM 0.0259 0.0280 0.020 0.021 MC atvynorth 0.0465 0.0681 0.364 0.532 MC atvysouth 0.0739 0.0752 0.399 0.406 MC DSECCID 0.0553 0.0399 0.325 0.235 MC ECCID 0.0435 0.0816 0.551 1.032 MC Outlet3 0.0227 0.0280 0.111 0.137 MC US30ALaruelOut 0.0236 0.0280 0.081 0.097 July 2011 62
Appendix A 3 Reservoir Information July 2011 63
EDITS TO RESERVOIR ELEMENTS IN THE MARSH CREEK MODEL Mark Boucher from the Contra Costa Flood Control and Water Conservation District provided a spreadsheet with the elevation storage discharge information for all of the reservoirs in the Marsh Creek model. Some of the reservoir curves had to be extended because the elevation computed with the HEC HMS model was above the elevation originally in the model. If data was available from the County then the curves were extended using that information. If there was no additional information then a combination of extrapolation and/or topographic information was used to extend the basin curves. The information below explains where the reservoir data came from and what changes were made. Basin Name in Model: 107 VYSouth Name from County information: Vinyards South Basin Source Information: County reports source as November 2005 Report by Balance Hydrologics for Vinyards at Marsh Creek Notes: the information provided by Contra Costa County was extended using the topographic data. Figure A3 1 below shows the 107 VYSouth basin and from the contour data it appears that the elevation storage discharge data provided by the county can be extrapolated to about elevation 137.5. At 138 the basin will start to experience weir flow. The elevation storage relationship up to elevation 138 was maintained but at 138 the discharge would start to increase to account for the weir flow. At this point the discharge at 138 was calculated using the standard weir flow equation. For this situation: / C = 2.6 (average coefficient for a broad crested weir) L = 86 feet (measured in GIS) H = 0.5 feet Q = 79.0 cfs July 2011 64
Figure A3 1. 107 VY Basin with contours and weir location Figures A3 2 and A3 3 below show the changes to the elevation storage and storage discharge curves. The values are listed in the table A3 1. 107 VY South Storage Discharge Storage (ac ft) 90 80 70 60 50 40 30 20 10 0 0 5 10 15 20 25 30 35 Discharge (cfs) Modified Storage Discharge Curve Original Storage Discharge Curve Figure A3 2. Reservoir 107 VY South Storage Discharge Curve July 2011 65
107 VY South Elevation Storage Storage (ac ft) 40 35 30 25 20 15 10 5 0 120 125 130 135 140 145 Elevation (ft) Modified Elevation Storage Curve Original Elevation Storage Curve Figure A3 3 Reservoir 107 VYSouth Elevation Storage Curve Table A3 1. Reservoir 107 VYSouth Elevation Storage Discharge Data Elevation (ft) Storage (ac ft) Discharge (cfs) 122 0 0 124 2.1 1.6 126 4.6 2.3 128 7.6 11.7 130 11.1 16.9 132 15 20.7 134 19.6 23.9 136 24.7 26.7 138 30.3 79.0 The last data point was added to the paired data tables in the model. July 2011 66
Basin Name in Model: 107 VYNorth Name from County information: Vinyards North Basin Source Information: County reports source as November 2005 Report by Balance Hydrologics for Vinyards at Marsh Creek Notes: A review of the aerial photo and topographic data shows an elevation of about 124 to 124.5 for most of the road that surrounds the basin. It was assumed that water will not overflow the basin at elevation 124 so the two curves were extended slightly to 124 and the corresponding data entered into the model. Figures A3 4 and A3 5 below show the changes to the elevation storage and storagedischarge curves. The values are listed in the table A3 2. 60 50 107 VYNorth Storage Discharge Discharge (cfs) 40 30 20 10 0 0 10 20 30 40 50 60 70 80 Storage (ac ft) Modified Storage Discharge Curve Original Storage Discharge Curve Figure A3 4. Reservoir 107 VYNorth Storage Discharge Curve July 2011 67
Storage (ac ft) 107 VYNorth Elevation Storage 80 70 60 50 40 30 20 10 0 105 110 115 120 125 Elevation (ft) Modified Elevation Storage Curve Original Elevation Storage Curve Figure A3 5. Reservoir 107 VYNorth Elevation Discharge Curve Table A3 2. Reservoir 107 VYNorth Elevation Storage Discharge Data Elevation (ft) Storage (ac ft) Discharge (cfs) 107 0 0 108 0.6 0.7 110 4.5 1.3 111 7.7 1.6 112 11.3 5.4 113.2 15.3 11.4 114 18.7 13.7 116 26.9 21.8 118 35.7 33.2 120 45.3 40.4 122 56 46.3 124 67.4 52.2 The last data point was added to the paired data tables in the model. July 2011 68
Basin Name in Model: 105 Deer Crk Basin Name from County information: None Source Information: County reports source as HYDRO2 Model in the Deer Creek Hydrology Report dated November 10, 1997, File No. 3105 04 Notes: the information from the County was extended by using ArcGIS to create 0.5 foot contours from the DEMs provided by the County. The area was calculated at the 95 and 98 contours and additional storage values were calculated. The equation in the County s spreadsheet was used to calculate the corresponding discharge values. A review of the topography and a review of the area in Google StreetView seems to show that water will not start flooding over the roads until the elevation reaches about 99 feet so it was assumed that the discharge equation used by the County would still be accurate at 98 feet. Figures A3 6 and A3 7 below show the changes to the elevation storage and storagedischarge curves. The values are listed in the table A3 3. 250 Deer Crk Basin Storage Discharge Discharge (cfs) 200 150 100 50 0 0 20 40 60 80 100 120 140 160 180 Storage (ac ft) Modified Storage Discharge Curve Original Storage Discharge Curve Figure A3 6. Reservoir Deer Crk Storage Discharge Curve July 2011 69
Deer Crk Basin Elevation Storage Storage (ac ft) 180 160 140 120 100 80 60 40 20 0 70 75 80 85 90 95 100 Elevation (ft) Modified Elevation Storage Curve Original Elevation Storage Curve Figure A3 7. Reservoir Deer Crk Basin Elevation Storage Curve Table A3 3. Reservoir Deer Crk Elevation Storage Discharge Data Elevation (ft) Storage (ac ft) Discharge (cfs) 77 0 0 79 0 48.12 81 6.5 83.34 83 17.5 107.59 85 33.5 127.31 87 48.5 144.35 89 66 159.59 91 87 173.49 93 105.7 186.36 95 120.7 198.4 98 154.1 215.2 The last two data points were added to the paired data tables in the model. July 2011 70
Basin Name in Model: 30C Fairview Name from County information: None Source Information: County reports source as HYDRO2 Model of unknown date Notes: the information from the County was extended by using ArcGIS to create 0.5 foot contours from the DEMs. It appears the basin will not experience weir flow until the water reaches about 98.5so the elevation storage discharges curves were extended slightly up to 98.5 feet. At 99 the basin will start to experience weir flow with water overflowing to the east northeast toward the Union Pacific Railroad, see Figure A3 8 below. The elevation storage relationship up to elevation 98.5 was maintained but at 99 the discharge would start to increase to account for the weir flow. At this point the discharge at 99 was calculated using the standard weir flow equation noted above assuming an effective weir length of 500 feet. Figures A3 9 and A3 10 below show the changes to the elevation storage and storage discharge curves. The values are listed in the table A3 4. Figure A3 8. 30C Fairview Basin with contours and weir location July 2011 71
30C Fairview Storage Discharge 500 Discharge (cfs) 400 300 200 100 0 0 20 40 60 80 100 120 140 Storage (ac ft) Modified Storage Discharge Curve Original Storage Discharge Curve Figure A3 9. Reservoir 30C Fairview Storage Discharge 30C Fairview Elevation Storage 120 100 Storage (ac ft) 80 60 40 20 0 82 84 86 88 90 92 94 96 98 100 Elevation (ft) Modified Elevation Storage Curve Original Elevation Storage Curve Figure A3 10. Reservoir 30C Fairview Elevation Storage Curve July 2011 72
Table A3 4. Reservoir 30C Fairview Elevation Storage Discharge Data Elevation (ft) Storage (ac ft) Discharge (cfs) 83.8 0 0 84 0.001 1.2 84.8 3.42 6 85.8 7.7 13.91 87.8 20 29.73 88.1 22.06 32.1 89.8 33.7 41.96 90.1 35.94 43.7 91.8 48.6 51.44 92.1 51.03 52.8 93.8 64.8 59.43 94.1 67.43 60.6 95.8 82.3 66.47 96.1 84.9 67.67 97.8 99.9 73.67 98.5 110 79.67 99 125 460 The last two data points were added to the paired data tables in the model. July 2011 73
Basin Name in Model: 30C Freedom (basin shapefile names this as 30C LibertyBas) Name from County information: None Source Information: County reports source as HYDRO2 Model of unknown date Notes: the information from the County was extended by using ArcGIS to create 0.5 foot contours from the DEMs. It appears the basin will not experience weir flow until the water reaches about 80.5 so the original elevation storage discharges curves were maintained up to 80 feet. At 80.5 it was assumed that the basin will start to experience weir flow with water overflowing to the east toward O Hara Street, see Figure A3 11 below. The elevation storage relationship up to elevation 80.5 was maintained but at 80.5 the discharge would start to increase to account for the weir flow. At this point the discharge at 80.5 was calculated using the standard weir flow equation noted above assuming an effective weir length of 150 feet. Figures A3 9 and A3 10 below show the changes to the elevation storage and storage discharge curves. The values are listed in the table A3 5. Figure A3 11. 30CFreedom Basin with contours and weir location July 2011 74
30C Freedom Storage Discharge Discharge (cfs) 450 400 350 300 250 200 150 100 50 0 0 10 20 30 40 50 60 70 80 90 Storage (ac ft) Modified Storage Discharge Curve Original Storage Discharge Curve Figure A3 12. Reservoir 30C Freedom Storage Discharge Curve 30C Freedom Elevation Storage 100 Storage (ac ft) 80 60 40 20 0 66 68 70 72 74 76 78 80 82 Elevation (ft) Modified Elevation Storage Curve Original Elevation Storage Curve Figure A3 13. Reservoir 30C Freedom Elevation Storage Curve July 2011 75
Table A3 5. Reservoir 30C Freedom Elevation Storage Discharge Data Elevation (ft) Storage (ac ft) Discharge (cfs) 66 0 0 66.3 0.15 0 68 1 17.94 68.3 2.24 21.1 70 9.3 28.75 70.1 9.85 29.2 72 20.3 35.9 74 32.4 41.8 76 45.6 46.9 78 59.9 51.6 80 74.4 56.6 80.5 80 390 The last data point was added to the paired data tables in the model. July 2011 76
Basin Name in Model: 30A Laurel Basin Name from County information: None Source Information: County reports source as HYDRO2 Model of unknown date Notes: the information from the County was extended by using ArcGIS to create 0.5 foot contours from the DEMs. Based on the topographic data it appears that the basin will be overflowing at 33 feet but due to the heavy vegetation to the northwest of the basin the LIDAR may be slightly off. It was assumed that the basin will not start overflowing until it reached 33.5 feet and then it will overflow to the northwest. Figure A3 14 below shows the 33 contour location and the assumed direction of overflow. The elevation storage relationship up to elevation 33.5 was maintained but at 33.5 the discharge would start to increase to account for the weir flow. At this point the discharge at 33.5 was calculated using the standard weir flow equation noted above assuming an effective weir length of 235 feet, figure A3 15 shows the location of the weir. Figures A3 16 and A3 17 below show the changes to the elevationstorage and storage discharge curves. The values are listed in the table A3 6. Figure A3 14. 30ALaurel Basin with contours and assumed direction of overflow July 2011 77
Figure A3 15. 30A Laurel Basin with contours and weir location 30A Laurel Storage Discharge 250 Discharge (cfs) 200 150 100 50 0 0 20 40 60 80 100 120 Storage (ac ft) Modified Storage Discharge Curve Original Storage Discharge Curve Figure A3 16. Reservoir 30A Laurel Bas Storage Discharge Curve July 2011 78
30A Laurel Elevation Storage Storage (ac ft) 120 100 80 60 40 20 0 20 22 24 26 28 30 32 34 36 Elevation (ft) Modified Elevation Storage Curve Original Elevation Storage Curve Figure A3 17. Reservoir 30A Laurel Bas Elevation Storage Curve Table A3 5. Reservoir 30A Laurel Bas Elevation Storage Discharge Data Elevation (ft) Storage (ac ft) Discharge (cfs) 20 0 0 21 0.1 4.6 22 0.3 8.5 23 1.9 10.5 24 6.9 12.2 25 14.2 13.6 26 22.4 15.1 27 31 16.4 28 40.3 17.7 29 50.3 18.8 30 61 19.8 31 72.4 20.8 32 84.3 21.7 33 96.2 22.6 33.5 108.2 216 The last data point was added to the paired data tables in the model. July 2011 79
Basin Name in Model: 104 UpSCBasin Source Information: topographic information and Sand Creek Storm Drain Improvements construction drawings dated July 1, 1994 Issue: The elevation storage discharge information in the model provided by the County reflected planned improvements to the Sand Creek basin. Since FEMA models existing conditions, the current elevation storage discharge relationships had to be calculated. To calculate the elevation storage relationships the submitted DEM was contoured at 0.5 feet intervals and the area of the basin at each 0.5 feet increment was totaled. To calculate the volume at each 0.5 foot increment the following formula was used: 6 Where: H = height between three successive 0.5 foot elevation increments B 1 = surface area of the base elevation B 2 = surface area of the middle elevation B 3 = surface area of the top elevation Total the cumulative storage volume at each 0.5 foot elevation yields the following elevation storage relationship, see Figure A3 17. The data used in the model is in Table A3 6. Elevation (ft) 200 180 160 140 120 100 80 60 40 20 0 Sand Creek Elevation Storage 172 174 176 178 180 182 184 186 188 190 Storage (acre ft) Figure A3 17. Sand Creek Elevation Storage Curve July 2011 80
Table A3 5. Sand Creek Reservoir Elevation Storage Data Elevation (ft) Storage (ac ft) 172.5 0.000 173.0 0.000 174.0 0.040 175.0 0.556 176.0 2.169 177.0 5.326 178.0 10.808 179.0 19.347 180.0 31.388 181.0 46.312 182.0 63.183 183.0 81.540 184.0 101.300 185.0 121.774 186.0 142.722 186.5 153.235 187.0 163.763 187.5 174.305 188.0 184.854 To calculate the discharge from the basin the outlet structures option was used. Contra Costa County provided a set of drawings titled Sand Creek Storm Drain Improvements dated July 1, 1994 that included information regarding the outlet from the basin. The major outlet is 42.4 feet of corrugated metal pipe that measures 54. The following information was used for this outlet, entrance and exit coefficients and Manning s n were obtained from the HEC RAS hydraulic reference manual. The scale was based on aerial photos and the construction drawings of the outlet. Table A3 6. Outlet Structure Information Shape Circular Chart 2: corrugated metal pipe Scale 2: mitered to conform to slope Length (ft) 42.4 Diameter (ft) 4.5 Inlet Elevation (ft) 172.5 Entrance Coefficient 0.7 Outlet Elevation (ft) 171 Exit Coefficient 1 Mannings n 0.024 July 2011 81
The construction drawings and photos also show two risers that act as emergency outlets but according to the drawings the elevation of the tops of the risers is 188, which is above the overtopping elevation for the basin so these risers were not included in the model. Based on the topographic data is appears that the basin will start to overtop to the east at an elevation just above 186 feet, flowing directly to Marsh Creek. To account for this the dam over tops function was also used. Figure A3 18 shows the basin with contours and the assumed weir location and length. Figure A3 18. Sand Creek basin with contours and weir location It was assumed that weir flow would begin at 186 feet and the length of the weir was estimated at 530 feet with a typical broad crested weir coefficient of 2.6. July 2011 82