Stormwater Management Modeling and Resiliency Adaptation to Protect Critical Infrastructure
- Martha E. Cardona, Pradeep Rayaprolu, Jonathan Rivas, Joseph L. Davenport, Gregory Bazydola
In October 2012 Tropical Storm Sandy impacted New York State, and especially areas of Nassau County on Long Island, causing widespread damage and disruption of public services. The Bay Park Sewage Treatment Plant (BPSTP) was one of many public infrastructure facilities severely impacted by flooding. In response, the County initiated design and construction of mitigation measures to protect the BPSTP from future flood surges. The primary flood proofing measure consisted of an 18.25-ft levee-floodwall combination that would help protect BPSTP from a storm surge equivalent to flood elevations observed during Sandy. Other critical flood proofing measures considered were enclosure structures at effluent locations to prevent backflow. As a result of sealing the facility below this critical elevation, an innovative approach was required to address the risk of localized flooding on the BPSTP property. Stormwater runoff at the plant is currently collected by a stormwater network and conveyed to two outfalls, which will be closed during a surge event to prevent backflow from entering the BPSTP. Therefore, two stormwater pumping stations were envisioned to manage coincident rainfall runoff at the facility.
Nassau County made use of an integrated network modeling approach to evaluate the drainage system performance including overland flow paths, water depths, and flooding duration. The model was used effectively to simulate runoff-related flooding, under open and closed slide gates scenarios, for multiple design storms. The results of the modeling of closed gate scenarios served as the basis of design for conveyance of the 10-yr storm via the two stormwater pumping stations, with less than 15-in flooding during both the 10-yr and 100-yr storms. The modeling effort also had the ancillary benefit of identifying under capacity existing infrastructure and system control points for further improvements to overall stormwater management. Furthermore, insight was gained into the BPSTP infrastructure’s ability to handle heavy rainfall and storm surges, providing a framework for similar resiliency studies at other vulnerable public infrastructure threatened by global climate changes.
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