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<br />. <br /> <br />Weather Service provided an isohyetal map of rainfall during the Agnes <br /> <br /> <br />flood and hourly rainfall data at recording stations. The Baltimore <br /> <br /> <br />District had previously conducted a comprehensive study of the Susquehanna <br /> <br /> <br />River Basin above Harrisburg, PA, the results of which were published in <br /> <br /> <br />Appendix D, "Hydrology." Susquehanna River Basin Study Report (reference 5). <br /> <br /> <br />The hydrology appendix delineated over 140 hydrologic subbasins and their <br /> <br />unit hydrograph characteristics. A map of the Susquehanna River Basin is <br /> <br /> <br />shown in figure 1. The report also specified the Muskingum routing cri- <br /> <br />teria for all of the reaches connecting the subbasins and forming the <br /> <br /> <br />river system. Reservoir storage characteristics, general operation criteria <br /> <br />and actual Agnes operating results were obtained from the Baltimore District. <br /> <br />The U.S. Geological Survey provided stream gage data where available and <br /> <br /> <br />made estimates of flows where gages were washed out. <br /> <br /> <br />The rainfall input to the rainfall-runoff model, HEC-l,was constructed <br /> <br /> <br />using the isohyetal rainfall pattern to determine average total rainfall <br /> <br />for each subbasin and the recorder data to distribute this total rainfall <br /> <br /> <br />period by period. Emphasis was placed on reproducing the observed volume <br /> <br /> <br />of runoff while maintaining the timing and magnitude of the peak within <br /> <br /> <br />reasonable limits. Samples of computed and observed hydro graphs at major <br /> <br /> <br />river stations are shown in figure 2. Table 1 summarizes pertinent data <br /> <br /> <br />about Agnes rainfall and runoff. <br /> <br /> <br />In order to be able to reconstitute the rainfall-runoff process for <br /> <br /> <br />Agnes. it was not necessary to use the reservoir system operation model, <br /> <br />HEC-5, because the observed reservoir releases could be given to the <br /> <br />HEC-l model. The observed reservoir outflows were inputed directly into <br /> <br /> <br />IIEC-l and runoff was computed only for the areas below the reservoirs. <br /> <br />The principal use of the reservoir operation model was for evaluation <br /> <br /> <br />of future changes in reservoirs, levees and channel improvements on regu- <br /> <br />lated frequency curves. <br /> <br />COMPUTATION OF FLOOD FLOWS IN THE WILKES-BARRE REACH <br /> <br />The rainfall-runoff model was used to compute the inflow to the <br /> <br />3 <br />