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Sea Level Rise: Human Impacts

When you live in the flattest U.S. state, in a “geological hotspot” that’s sinking, where the sea has already risen a little over a foot in the past century and is predicted to keep on rising, “it loads the dice when storms occur,” says Gerald Kauffman.

Kauffman, director of the Water Resources Agency, and associate scientist Andrew Homsey, both based at UD’s Institute for Public Administration, recently published a report on the 331 square miles, or 17 percent of Delaware’s land mass, that lies within the 100-year floodplain.

Based on recent FEMA flood insurance studies and other data, they found that more than 18,000 structures exist in this area:

  • 2,431 in New Castle County,
  • 1,853 in Kent County and
  • 13,760 in Sussex County.

The watersheds with the most structures in the 100-year floodplain include the Christina River in New Castle County (1,007 structures); St. Jones River in Kent County (567 structures); and Indian River Bay in Sussex County (3,856 structures).

Also, approximately 621 road miles lie in this floodplain:

  • 128 miles in New Castle County,
  • 75 miles in Kent County and
  • 418 miles in Sussex County.

Watersheds with the most road miles in the floodplain include the Christina River in New Castle County (44 miles), the Murderkill in Kent County (16 miles) and Indian River Bay (106 miles) in Sussex.

With sea level rise comes increased flood risk to residents living in these areas. After massive flooding of the Glenville subdivision along Red Clay Creek near Stanton from Tropical Storm Henri in 2003, state and local government bought out the homes, and the community was abandoned.

For public safety in the face of sea level rise, Kauffman, who is a member of the state’s Climate Change Vulnerability Steering Committee, advises strengthening building codes by instituting new permissible standards moving up from the 100- to 500-year floodplain, as well as beefing up the size and height requirements for infrastructure such as roads, dams and bridges.

Kauffman points out that climate change and rising seas already are affecting the ebb and flow of daily life in Delaware, toward a “new normal.”

“School districts are reconfiguring their bus routes for portions of Route 9 that typically flood during a storm,” he says. “People call us about how much warmer their drinking water is in summer, and blue crabs have been as far north as Delaware racetrack.”


Gerald Kauffman, director of the Water Resources Agency at UD, prepares to measure the height of the water surface in White Clay Creek near Newark, Del.  »