Flooding Risk Rises for East Coast as Waters Recede in South Carolina and Georgia

According to catastrophe risk modeling firm, RMS, persistent onshore winds coupled with monthly spring tides led to higher than predicted tides and coastal flooding across parts of South Carolina and Georgia this week causing localized property damage.

Commenting on the floods, Emily Paterson, senior manager of the event response team at RMS, said that while many areas of South Carolina are still recovering from the severe rainfall and flooding event that inundated the state earlier this month, “the worst of flooding is likely now over for South Carolina and Georgia.”

Hurricane Joaquin caused water to be driven onshore as a result of the pressure gradient between an area of high pressure centered over the Northeast U.S. and a low pressure area over the northern Gulf Coast.

Tides peaked at 8.68 feet above mean lower low water (MLLW) in Charleston Harbor, the location’s fourth highest tide since records began in 1921.

Only three recorded events have produced higher tides at Charleston Harbor; Hurricane Hugo in September 1989 (12.56 feet), an August 11, 1940 hurricane (10.27 feet), and a New Year’s Day 1987 coastal storm (8.84 feet). According to Paterson, major coastal flooding at this location typically occurs when gauge levels reach 8 feet above MLLW.

The tide level this week was around 5 in (125 mm) higher than the peak measured earlier this month during the South Carolina flooding and coastal flooding event, though no heavy rainfall occurred concurrently, said Paterson.

Along the Georgia coast, near Savannah, tides peaked at 10.43 feet above MLLW, at the Ft. Pulaski river tide gauge, the third highest recorded since 1935. Even including hurricanes, this is the third highest recorded tide at Fort Pulaski on record since 1935. Only two hurricanes have produced higher tides above MLLW at this location; a hurricane in October 1947 (10.87 feet) and a hurricane in August 1940 (10.47 feet). Major tidal flooding at this location typically begins when the gauge levels reach 10 feet above MLLW, Paterson said.

Elsewhere, minor flooding inundated some streets in Miami Beach, Delray Beach and West Palm Beach, Fla., with minor flooding also reported in Waveland, Miss., and Slidell, Louisiana.

Source: RMS