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Flood risks in the northeastern US are an acute and growing concern. Widespread flooding from recent hurricanes Irene and Lee as well as Super-Storm Sandy have garnered national and international attention, and many more localized flash flood events pepper the region with perceived increasing frequency. Projections of more frequent large or high intensity rainfall events, combined with expanded development of currently rural landscapes, suggest that flood risks will continue to escalate and that assessing the capacity and quality of our stormwater infrastructure is of increasing importance.

What’s the problem?

Culverts, which are pipes designed to carry runoff or stormflow under roadways, can be circular or square, metal or concrete and to function properly must be correctly sized for the upstream area that drains to them. As we adapt New York’s infrastructure to a changing climate, identifying undersized culverts is important for flood mitigation and prevention, as well as for preventing damage to roadways and streams. 

What are we doing?

The primary goal of this project is to inventory and assess the location and capacity of existing culverts. Records on the location and size of existing culverts in New York are lacking, made scarce by the fact that stormwater infrastructure is owned and maintained by many different entities—the State DOT, county governments, and individual municipalities. The number of culverts located in a municipality or watershed varies; it is dictated by the amount of development and the amount of water in the area. Through this project, field teams are sent to specific watersheds and counties around the state to locate and measure each culvert. In the field, many of these teams are collecting additional data on each culvert to be used in WRI’s “Aquatic Connectivity and Barrier Removal” project. 

Our computer model, using tools written in Python and ArcMap, takes the culvert measurements from the field team along with USGS elevation and streamflow data to calculate the capacity of each culvert. Taking this capacity information and comparing it to current records and future projections of precipitation from the Northeast Regional Climate Center, the model reports the maximum storm size that each culvert can withstand without causing flooding.