Fortified Tidal Crossing Will Stand Strong against Climate Change

A town’s culvert is now large enough to repel the next 100 years of intensifying hazards—and more tidal crossing fixes are on the way, thanks to a process co-led by the New Hampshire Coastal Program.

Not long ago in Newmarket, New Hampshire, an undersized culvert caused regular road flooding. In place of that old structure now stands a culvert nearly 9 feet deep by 16 feet wide. Built for the coming century’s highest tides and “100 year” flood conditions, it enables fish to swim from Great Bay upstream to critical rearing habitat in Lubberland Creek for the first time in decades. A state partnership that assessed this tidal crossing and 117 others was co-led by The Nature Conservancy and the New Hampshire Coastal Program, with support from NOAA’s Office for Coastal Management.

Partners in the New Hampshire Tidal Crossing Assessment Protocol are working with road agents on engineering and design solutions to make four more New Hampshire crossings stronger and safer.

The protocol ranked and prioritized tidal crossings in 17 coastal communities according to structural problems, flood risk, tidal restriction, and limitations on fish passage and salt marsh migration. It identified 23 crossings most in need of repair or replacement plus another 32 crossings needing significant attention.

Partial funding for the protocol, from NOAA’s Office for Coastal Management, was administered by the New Hampshire Coastal Program, part of the state’s Department of Environmental Services. (2019)

More Information: “Climate Ready” Great Bay Culvert

Partners: New Hampshire Department of Environmental Services Coastal Program, The Nature Conservancy, University of New Hampshire, and University of New Hampshire Technology Transfer Center

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