Storm Surge Barrier Closure Frequency, Duration and Trapped River Flooding Analysis

Gated storm surge barriers are being considered by the Corps of Engineers as one of a number of options for coastal storm risk management for the New York City metropolitan area. Surge barriers typically span the opening to a harbor or river mouth and include gates that are only closed when storm surges exceeding a specific water level or return period are expected. Gate closure frequency and duration both strongly influence the effects of a surge barrier system on the enclosed estuaries. Also, during a storm surge, closed gates may trap streamflow and cause a new problem with trapped river water flooding. In this project we statistically evaluate multi-variate hazards, including the gate closure frequency and duration and how they change with sea level rise, as well as the potential for trapped water flooding from trapped river water. Not only does sea level rise cause an amplification of the frequency of water level exceedances (and corresponding gate closures), it causes a lengthening of the closure duration. These results are helping the Corps understand potential management regimes and better estimate costs and benefits for surge barriers.