Orestimba Creek Hydrology - Stanislaus County

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Orestimba Creek Subarea 4ORSUB4Main 5-day Wave for All Frequencies300250200Flow in cfs15010050018 19 20 21 22 23Time in Days20% 10% 2% 1% 0.05% 0.02%Figure 13. Orestimba Creek Subarea 4, Main 5-Day Wave for All FrequenciesOrestimba Creek Subarea 4ORSUB41 Percent Probability Flood 30-Day Series180160140120Flow in cfs1008060402001 6 11 16 21 26Time in DaysFigure 14. Orestimba Creek Subarea 4, 1 Percent Probability Flood 30-Day Series5. SUMMARY AND RECOMMENDED USE OF FLOOD FREQUENCY ANALYSISAND FLOOD HYDROGRAPHSThe updated frequency curves in this report include additional years of record (a total of 75 years ofcredible data) and additional volume-duration analysis. The influence of stream geomorphology andclimate was also considered in developing the final frequency curves. The great similarities of the32
statistics of the upper quartile of flows between Orestimba and Del Puerto creeks helped todetermine reasonable and more positive skew for Orestimba Creek. It is recommended that riskanalysis use 75 years of record to determine its confidence bands. The 2001 West Stanislausfeasibility study and subsequent reports had different hydrographs for different duration floods fordifferent report alternatives. There are substantial changes in the revised hydrographs over thefeasibility study’s hydrographs. The peak, 24 - and 72-hour hydrographs are now, on average, over20 percent lower. The 15-day has decreased an average of 13 percent. Table 13 compares the 2001study’s frequency and flood hydrograph peaks and volumes with the updated floods.This report has only one flood series for each of its six frequencies. The hydrographs are provided inthe appendix of this report and can be made available in an Excel or DSS format. The hydrographsare in 720 one-hour time periods or for 30-days. Shorter durations may be extracted. To ensureproper timing, always use the same start day and hour for all the hydrographs (see Table 12 for thestart day for each wave). For example, the whole 30-day series may be used for sizing storagefacilities. The maximum 5-day series starts on day 16. The maximum 10-day series starts on day 11.The maximum 15-day series also starts on day 11.Table 13Orestimba Creek near NewmanComparison of 2001Feasibility Study Flow Values with the 2008 Updated FlowsComparison of 2001 Feasibility Study Frequency Curvewith 2008 Updated Frequency CurvesComparison of 2001 Feasibility Study Rainfall-RunoffHydrographs with 2008 Updated Hydrographs2001 FFA Frequency Curve Flow2001 Rainfall-RunoffFlows from Model RunsPercent Peak 1-day 3-day 7-day 15-day Peak 24-hr 72-hr 15-dayProbability cfs day-cfs day-cfs day-cfs day-cfs cfs day-cfs day-cfs day-cfs0.2 27,100 8,990 5,450 2,770 1,820 25,258 12,293 5,807 1,8201.0 19,800 6,760 4,120 2,130 1,390 18,437 8,974 4,239 1,3902.0 16,200 5,650 3,440 1,810 1,170 15,118 7,358 3,476 1,17010.0 7,680 2,870 1,760 974 613 7,190 3,500 1,653 6132008 Updated FFA Frequency Curve Flows 2008 Updated Flood Hydrograph Flows0.2 20,255 7,398 4,823 3,039 1,685 20,255 9,231 4,785 1,6851.0 13,831 5,035 3,249 2,052 1,196 13,831 6,168 3,194 1,1962.0 11,208 4,093 2,626 1,657 985 11,208 4,996 2,588 98510.0 5,679 2,132 1,344 838 516 5,679 2,529 1,310 516Updated Flows as Percent of 2001 Flows0.2 75% 82% 89% 110% 93% 80% 75% 82% 93%1.0 70% 74% 79% 96% 86% 75% 69% 75% 86%2.0 69% 72% 76% 92% 84% 74% 68% 74% 84%10.0 74% 74% 76% 86% 84% 79% 72% 79% 84%Updated Flows as Percent Decrease of 2001 Flows0.2 25% 18% 11% -10% 7% 20% 25% 18% 7%1.0 30% 26% 21% 4% 14% 25% 31% 25% 14%2.0 31% 28% 24% 8% 16% 26% 32% 26% 16%10.0 26% 26% 24% 14% 16% 21% 28% 21% 16%Average Decrease for All Durations without Regard to Volume28% 24% 20% 4% 13% 23% 29% 22% 13%33
Page 1: Orestimba Creek HydrologyA Reevalua
Page 4 and 5: 8. Del Puerto Creek Flood Volume Ma
Page 6 and 7: Figure 1. General Map4
Page 8 and 9: Photo 2. Orestimba Creek, looking s
Page 10 and 11: The current analysis included an ad
Page 12 and 13: TABLE 2ADel Puerto Creek near Patte
Page 14 and 15: Orestimba Creek near NewmanAccurate
Page 16 and 17: Table 4FFA Results for Orestimba Cr
Page 18 and 19: TABLE 5AOrestimba Creek near Newman
Page 20 and 21: TABLE 5BOrestimba Creek near Newman
Page 22 and 23: TABLE 7Salado Creek at DamsiteFlow
Page 24 and 25: Figure 4. Translation of average na
Page 26 and 27: Figure 5. Subarea Map. Report hydro
Page 28 and 29: Orestimba Creek Flood Volume Durati
Page 30 and 31: Table 9 shows the ratios of Orestim
Page 32 and 33: Orestimba Creek Near Newman, CA(at
Page 36 and 37: 6. REFERENCESa. U.S. Army Corps of
Page 38 and 39: 36Chart 1
Page 40 and 41: 38Chart 3
Page 42 and 43: 40 Chart 5
Page 44 and 45: Table A1Orestimba Creek Flood Hydro
Page 58 and 59: PeriodDay-hrTable A3Crow Creek Loca
Page 70 and 71: Table A5Orestimba Creek Local Flowf
Page 82 and 83: PeriodDay-hrTable A7Orestimba Creek
Page 84 and 85:
PeriodDay-hrTable A7Orestimba Creek
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Orestimba Creek Hydrology - Stanislaus County

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