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The rainfall for the 500 -year frequency event was estimated <br />by extrapolation of the 10-, 50, and 100 -year frequency <br />events on probability paper. The 24-hour storm was determined to <br />be critical for the area at Chevy Chase Drive, the ponds east of the <br />French Lake area, the unnamed tributary to Stubb's Bay, and the <br />area near Carman Bay. The 10 -day snowmelt event was determined from <br />the S.C.S. National Engineering Handbook (Reference 7) to be <br />critical for the ponds east of the French Lake area. The amount of <br />runoff for the 25-, 50- and 100 -year event was determined from the <br />Soil Conservation Service's National Engineering Handbook (Reference <br />7) for the ponds east of the French Lake area. The discharges for <br />the 10- and 500 -year frequency events were estimated by extrapolating <br />the 25-, 50- and 100 -year frequency events on probability paper. <br />Stage -discharge and stage -storage relationships were developed <br />for each hydraulic structure in the watersheds of the area at <br />Chevy Chase Drive, the ponds east of the French Lake area, and the <br />unnamed tributary to Stubb's Bay by using 2 -foot contour maps <br />developed from aerial photography (Reference 2), field investiga- <br />tion, U. S. Geological Survey topographic maps (Reference 10), <br />and culvert nomographs (Reference 18). Only stage -storage <br />relationships were developed for the ponds near Carman Bay since <br />the pord4 were considered land -locked. The previously mentioned <br />aerial photography and U. S. Geological Survey topographic maps <br />were used to determine the stage -storage relationships in addition <br />to a field investigation of the study area. The stage -discharge <br />and stage -storage relationships for the area at Chevy Chase Drive <br />and the unnamed tribunary to Stubb's Bay were made a part of <br />the TR -20 hydrologic computer model of the study areas. <br />For the ponds east of the French Lake area and the ponds near <br />Carman Bay, computations were made by iterative methods to develop <br />the water surface elevations for the selected frequencies. Inflow <br />into the first of the series of ponds was calculated by using the <br />TR -20 computer program (Reference 5). Culvert nomographs <br />(Reference 18) and standard routing methods were used to develop / <br />%pfd• :tiK <br />-41 ��./ •L <br />8 � <br />