Gull Harbor Gets Ready: Forecasting Storm Surge

Report to the Gull Harbor Town Council

1Gull Harbor is a fishing town on a low, sandy stretch of the southeastern U.S. coast. Most homes sit less than 3 m above the normal high-tide line. The town's hazard planning team, led by emergency manager Celeste Varga, looked at 50 years of records to plan for the next storm season.

2Hurricanes and tropical storms form over warm ocean water. As a strong storm comes ashore, its winds push ocean water toward the coast and raise the sea level for a few hours. This rise is called a storm surge, and it causes much of the flooding along low coasts. Surge height depends on more than wind speed: the size of the storm, its path, the shape of the coastline and the tide can all change how high the water climbs. The graph below counts every hurricane or tropical storm whose center passed within 100 km of Gull Harbor in the last 50 years, sorted by month. No storms passed that close from December through May.

3Forecasters can usually track a hurricane several days before it reaches land, using satellites, aircraft and ocean buoys. Their forecasts of a storm's path and strength give towns time to close storm shutters, move boats and help people leave. Past records cannot tell the town the exact date of its next storm, but they can show which months carry the most risk and how high the water has risen before.

4After the large flood of 2012, Gull Harbor restored its low sand dunes with beach grass and raised about 300 of its lowest homes onto pillars. The town has kept growing since then, and it has more homes near the water now than it had in 1998. The team now wants to know whether those steps worked and what to build next. Its report lists the five storms that flooded part of the town and compares four projects the council could build.