The Sleeping Giant: The Story of the Mt. Morris Dam (Rochester History, Summer 1996, Vol. LVIII, No. 3)

16 pp. The Mount Morris Dam is a concrete dam on the Genesee River. It is located south of Rochester, New York in the towns of Leicester and Mount Morris in Livingston County, New York, next to Letchworth State Park. The Mt. Morris Dam was built between 1948 and 1952 by the Buffalo District office of the U.S. Army Corps of Engineers (USACE). The project was authorized by the United States Congress in the Flood Control Act of 1944 at a cost of $25 million. Prior to the construction of the dam, the Genesee River Valley and the city of Rochester had experienced periodic flooding. The flood of 1865, which developed flows exceeding 24 million U.S. gallons (91 megaliters) per minute, resulted in massive destructions with flows equating half the flows of Niagara Falls. Severe floods occurred every seven years on average between 1865 and 1950. Prior projects in Rochester, including retaining walls and a deepening of the river, were insufficient to stop a major flood event. The USACE states that, in the years since the completion of the dam, an estimated $1 billion in flooding damages have been prevented. In June 1972, Hurricane Agnes passed over the Genesee Valley, causing over 7 inches of rain to fall across the entire valley in a short period of time. The water inflow due to Hurricane Agnes exceeded the storage capacity of the reservoir and it was necessary to release water through the gates of the dam, causing minor downstream flooding. These releases were made to prevent overtopping of the spillway. Had the spillway overtopped, accumulated debris in the reservoir would have passed downstream, causing log jams and additional damage. Inflows of this magnitude are only expected to happen an average of every 300 years. An estimated $210 million in damages was prevented by the dam during the storm.