MODELING THE GENESEE RIVER FLOOD OF 1972

The Mount Morris Dam was constructed 35 miles upstream of Rochester, NY on the Genesee River by the Army Corps of Engineers in the 1950’s to provide flood protection for the area. In June of 1972, the remnants of Hurricane Agnes combined with a low pressure system to drop several inches of rain on the east coast of the U.S., including the entire Genesee River watershed. During this event, areas upstream of the Mount Morris dam received 6 to 16 inches of rain in a 5 day period, with most of the rain falling in the first 3 days, while areas downstream of the dam received less than 5 inches of rain. Extreme rainfall upstream generated heavy flow volumes which are displayed by a sharp curve on the upstream hydrograph followed by a quick return to base flow. However, downstream areas received significantly less rain and lower flow volumes. This is displayed by a less extreme peak on the hydrograph followed by flows above base level for a longer period of time.

By using the modified Puls flood routing method, the heavy flow volumes received upstream were tracked going into the dam from an upstream site at Portageville, NY, while the water filled up the Mount Morris dam, and as the water exited the dam and reached a downstream site at Rochester, NY with a modified version of the continuity equation. This generated an outflow hydrograph on what the expected flow volumes would be at Rochester which was compared to the actual recorded flows. The hydrographs were similar in shape, and when conducting the Nash-Sutcliffe hydrograph significance test, an error of 12% was found. This percent error can be contributed to the fact that Rochester is 35 miles downstream of the dam, downstream groundwater input, downstream rainfall, assumed rates at which the Mount Morris dam filled up, and the inflow of downstream tributaries.