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Culvert Prioritization Project

The Hudson River Estuary Program and its partners work to reduce flooding risks to communities and restore aquatic habitats by supporting culvert assessment and prioritization.

 

Culvert assessment in actionFlood 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.

Field assessment

Culvert assessment map, August 2018
Road-stream crossings assessed for passability and capacity, updated August 2018.

The Hudson River Estuary watershed likely contains more than 10,000 culverts. Records on the location and size of existing culverts are lacking, made scarce by the fact that stormwater infrastructure is owned and maintained by many different entities—the State DOT, county governments, individual municipalities, and private landowners. 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 in the Estuary watershed boundary to locate and measure each culvert.

As of September 2018, Estuary Program staff and partners assessed 46.9% of the Estuary’s culverts, and are on track to achieve the Hudson River Action Agenda goal of 50% by 2020.

The Estuary Program follows the North Atlantic Aquatic Connectivity Collaborative protocol for culvert assessment, and offers the NAACC field training component required to become a Lead Observer (typically in May).

Culvert capacity modeling

Culvert evaluation process. Modelling steps are outlined in blue.

Faculty, staff, and students at Cornell University and the NYS Water Resources Institute developed and maintain a culvert capacity model, using ArcGIS hydrology tools and Python. Given a culvert location and dimensions, the model predicts a contributing watershed area for the culvert, determines current and future (2050) peak flows in the watershed, then compares this to the culvert capacity to estimate the current and future maximum passable storm event.

Please note, the Cornell Culvert Model can be used to help prioritize culverts for replacement projects. It should not be used in place of an engineering assessment.

Bad culvertMunicipal Management Plans

Estuary Program staff use the field assessment data and capacity model outputs to support municipalities in creating "Municipal Management Plans." These documents catalog all culverts in a municipality's jurisdiction, and prioritize them for replacement based on flooding risk, condition of the crossing, and potential for increasing the length of contiguous aquatic habitat. Municipalities can use these documents as a long-term resource to plan and apply for funding to support culvert right-sizing and repair.