Coastal Change Hazards: Hurricanes and Extreme Storms

Storm-Impact Scale

Collision Regime

Collision Regime Net dune erosion

If wave runup exceeds the elevation of the base of the dune, the runup will collide with the dune causing erosion and dune retreat. Unlike the temporary changes of the swash regime, this change is considered a net, or (semi-) permanent, change to the dune.

Dune Erosion During the Collision Regime

Extensive dune erosion along the Outer Banks of North Carolina after Hurricane Isabel's 2003 landfall reveals the remains of a shipwreck on the beach near the town of Buxton. [larger version]

Below are a pair of before and after Hurricane Fran photographs show that the system was in Collision Regime, with significant dune retreat.

Before: July 1996, Hurricane Fran, Topsail Island, NC.

After: September 1996, Hurricane Fran, Topsail Island, NC.

Below are cross-sections of lidar data showing dune retreat of 20 meters during Hurricane Dennis (1999).

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