Downstream Effects Resulting from the Operation of the Pompton Lake Dam Floodgates

The Governor’s Passaic River Basin Flood Advisory Commission charged the New Jersey Department of Environmental Protection (NJDEP) with evaluating the operational impacts of the Pompton Lakes Dam Floodgate Facility. NJDEP retained AECOM to develop a hydraulic computer model to simulate the downstream impacts resulting from the operation of the facility.
The floodgate facility provides an unconventional approach to flood mitigation. Unlike most flood control projects involving dams, the project provides flood reduction benefits to upstream residences only. The project was designed to have no benefits or negative impacts to downstream floodplain communities.
The AECOM study included approximately 5.50 miles of the Ramapo River (including Pompton Lakes) and 0.17 miles of the Pompton River. The study focused on the floodway/floodplain area downstream of the Pompton Lakes Dam, which is within the Borough of Pompton Lakes and Wayne Township. The analysis began at the downstream face of the Route 287 Bridge (Ramapo River crossing), continued downstream, and terminated at the Jackson Avenue Bridge (Pompton River crossing), approximately 11,500 feet downstream of the Pompton Lakes Dam. Tributaries to the Ramapo that may be affected by backwater were also studied; these included the Wanaque and Pequannock Rivers