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DOWNSTREAM EFFECTS OF THE LEVEE OVERTOPPING AT WILKES-BARRE, PA, DURING TROPICAL STOR~ AGNES(l) By Arlen D. Feldman(2) ABSTRACT A rainfall-runoff model for Tropical Storm Agnes in the Susquehanna River Basin was developed. A reservoir operation model was also developed in order to compute regulated streamflows. Susquehanna River flood dis- charges were computed for Wilkes-Barre. PA, for both levee nonovertopping and levee overtopping conditions. The levee overtopping conditions were modeled using storage-outflow relations developed from water surface pro- files for the Wilkes-Barre reach. If the levee had been sufficiently high to contain the flow, the peak discharge would have been increased and occurred earlier. Translating this earlier and larger peak downstream would have resulted in practically a 10 percent increase in the peak dis- charge at Sunbury. This large peak is due to both the increased peak at Wilkes-Barre and coincident timing with the peak coming from the West Branch of the Susquehanna River. Since the actual peak flow at Sunbury was within inches of the top-of-levee, a potentially disasterous flood could have occurred at Sunbury if the Wilkes-Barre levee had not been overtopped. BACKGROUND FOR THE STUDY The Hydrologic Engineering Center was requested by the Corps of Engineers, North Atlantic Division, to participate in a special hydrologic study of Tropical Storm Agnes, June 1972, in the Susquehanna and three other east coast river basins. The flood waters produced by Agnes rain- fall along with local frontal storms produced record flooding in many parts of the Susquehanna River Basin. The town of Wilkes-Barre, PA, was particularly hard-hit when flood waters overtopped the levees and inun- dated the flood plain on which most of the city was built. Cities down- stream from Wilkes-Barre were also flooded, but the severity of the (l)For presentation at the 54th Annual Meeting of American Geophysical Union, April 1973, Washington, D.C. (2)Research Hydraulic Engineer, The Hydrologic Engineering Center, U.S. Army Corps of Engineers, Davis, California.