Orestimba Creek Hydrology - Stanislaus County

Figure 6. Orestimba Creek HMS Model Routing Diagram. Computed hydrographs are underlined.Figures 7 and 8 summarize frequency peaks and volumes, determined in Section 3, with masscurves and tables.All flood hydrographs for the Orestimba Creek model are based on the 1 percent 96-hour rain floodhydrograph shape from the 2001 West Stanislaus feasibility report (Reference b). The storm wascentered over Orestimba Creek above the gage. Concurrent storms were developed for the sixsubbasins that flow into Orestimba Creek below the gage. The flood hydrograph volumes from thisstorm were adjusted to closely match the 3-day and 96-hour volumes of the Orestimba Creek 1percent mass curve (see Figure 7). The 5-day volume from this hydrograph is the main 5-day waveof the 30-day series. The other 5-day waves are based on the volume ratios from the frequencycurves. The main 5-day waves for the remaining floods are ratios of the 1 percent main wave. TableA 1 (see appendix) shows the tabulation of Orestimba’s 30-day hydrographs. The 6-wave 30-dayconcurrent Crow Creek hydrograph above I-5 used the 5-day 1 percent flood as the main wave. Theremaining 5 waves were based on volume ratios from the Del Puerto Creek mass curve, Figure 8.25