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<br />? <br />C ,r' r> , <br />/ <br /> <br />Wilkes-Barre Reach of the Susquehanna River during Tropical Storm Agnes. <br /> <br /> <br />The aforementioned rainfall, loss rate. unit graph and linear routing <br /> <br /> <br />criteria were used to compute this flow. Although the linear Muskingum <br /> <br /> <br />r~~ting_~E~teria was no~theoretically applica~e in some of the routing <br /> <br />reaches during the high flows of Agnes, the inflow to the Wilkes-Barre <br /> <br /> <br />Reach and the flows in most other parts of the basin appear to be Rood <br /> <br /> <br />estimates of the observed flows when using the linear routing. The <br /> <br />closest upstream verification was at The Towanda. PA. gage and the com- <br /> <br />parison of computed and observed discharges were shown in figure 2b. <br /> <br />Flood routing through the Wilkes-Barre Reach was accomplished by <br /> <br /> <br />two different methods. First, the flows were routed by the linear Muskingum <br /> <br />criteria assuming that the levees were sufficiently high to contain the <br /> <br /> <br />Agnes flood flow. Second, the flows were routed by a nonlinear storage- <br /> <br /> <br />outflow method (modified Puls) considering the existing topography and <br /> <br />levee heights in the reach before the flood. <br /> <br /> <br />The results of the two routings are shown in figure 3. The peak <br /> <br /> <br />discharge of the linear routing is seen to be 27,000 cfs larger than the <br /> <br /> <br />nonlinear routing and 17,000 cfs larger than the observed peak discharge. <br /> <br />The peak discharge for the nonlinear routing is 10,000 cfs less than the <br /> <br />observed peak discharge. <br /> <br /> <br />It was difficult to simulate the levee overtopping condition at Wilkes- <br /> <br /> <br />Barre because of the manner in which the event occurred. The flood waters <br /> <br /> <br />were not believed to have eroded the levee on the rising limb of the hydro- <br /> <br />graph. Inspection of the levee area after the flood indicated that the <br /> <br /> <br />levee did not erode upon overtopping, but erosion occurred as flood waters <br /> <br />returned to the river channel on the falling limb of the hydrograph. Because <br /> <br />of the difference in storage volumes before and after the levee eroded. it <br /> <br /> <br />was necessary to develop two storage-outflow relationships for the \Jilkes- <br /> <br />Barre reach--one for the rising and another for the falling limb of the <br /> <br />flood hydrograph. <br /> <br /> <br />The two storage-outflow curves for the Wilkes-Barre reach were computed <br /> <br /> <br />with IIEC-2, Water Surface Profiles. In the first case levees were considered <br /> <br />. <br /> <br />4 <br />