Brass Discs Against the Sea: How Coastal Parks Measure What the Next Storm Will Flood

In October 2012, Hurricane Sandy flooded parts of the Northeast coast under more than eight feet of water and hit nearly 70 national park sites; Fire Island National Seashore and Gateway National Recreation Area were among the hardest hit. Rebuilding raised a basic question for every historic fort, lighthouse and statue on the coast: exactly how high above the water does it sit?

A starting point for change

"In order to measure change, you have to know where you started measuring from," says Neil Winn, a geographer and GIS specialist at Assateague Island National Seashore. With precise elevation data, researchers can track how land and water levels have shifted, and how the ground beneath structures has changed.

Even before Sandy, the National Park Service had begun building that foundation. With the University of Rhode Island's Environmental Data Center, it installed networks of backbone monuments in ten northeast coastal parks:

• steel rods driven deep into the ground, capped with brass discs, each with a precisely measured elevation;
• placed where each park chose, often near infrastructure or significant sites;
• reference points from which survey equipment can measure a nearby structure's height to within 2–4 centimeters.

Installing elevation markers. Credit: NPS photo/Harpers Ferry Center.

After Sandy

The Department of the Interior awarded nearly $21 million to the NPS Northeast Region to study coastal systems and help parks prepare for future storms. Part of it paid to measure the first-floor heights of key buildings and structures — possible because the monuments were already in place — including the Statue of Liberty. Those heights show how vulnerable each cultural resource and visitor facility is to rising seas and storms, and help parks decide what to protect, move or strengthen.

Moving the utilities upstairs

At Gateway's Fort Hancock on Sandy Hook, New Jersey, Sandy had flooded basements and other low-lying spaces. With accurate first-floor elevations, the park moved utilities and heating systems up from the bottom floors, limiting the damage the next storm can do.

With these markers and the research that relies on them, parks can anticipate change and make science-based decisions to protect their historic places through what are likely to be more frequent and intense storms.

Sources

Based on "Protecting Coastal Treasures from Future Floods" by Minh Phan, from the National Park Service, a work of the United States government in the public domain.