The Project

Tropical Storm Irene caused significant flood damage in 2011 across the 96‐square mile Poesten Kill watershed. The Rensselaer Plateau Alliance (RPA) saw an opportunity and secured funding in 2018 from Hudson River Estuary Program (HREP) and New England Interstate Water Pollution Control Commission (NEIWPCC) to develop a plan with a goal to reduce the flood damage in future storms. RPA hired The Chazen Companies with subcontracted services of Interfluve P.C. to assist with the analysis. The team conducted public meetings and developed a watershed working committee to consider and advance specific stormwater opportunities.

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The working committee, consisting of local residents and representatives of the towns and city governments, helped the engineers and scientists of Chazen and Interfluve understand the history and local impacts of Irene and other storms. The committee also contributed ideas for flood mitigation strategies. In fact, an innovative strategy came out of this process: The idea to build naturally‐based or lightly engineered outlet controls at certain wetlands in the watershed that meet certain conditions. While this system does not interfere with streams flowing from wetlands during normal circumstances, in the event of a 25 year or bigger flood, they would slow the flow from the wetlands down just enough to reduce the peak flooding in the watershed below. Modeling shows that this strategy could reduce downstream flooding by more than half a foot during future floods, meaning the difference between overtopping flood walls in the City of Troy and staying within the walls; reducing damage to agricultural lands and structures; and allowing continued use of existing bridges and culverts. The wetland outlet controls also “work with nature” rather than requiring big earthmoving projects and are astonishingly cost‐effective to construct.