Pre- and Post-Storm Photo Comparisons - Introduction
On Friday December 4, 2009 USGS scientists acquired oblique aerial photographs from an altitude of about 150 m from Assateague Island, MD to Cape Hatteras, NC. These images were acquired roughly 2 weeks after the last effects of Nor’Ida were felt along the coast and were compared to photographs taken on May 21, 2009 (MD and VA coasts) or May 6, 2008 (NC coast). Some recovery of the intertidal beach may have occurred before the post-storm imagery was obtained. The recovery of dunes and areas landward occurs over longer time scales; hence, any observed changes of the dunes are assumed to be the result of Nor’Ida and any other storms that might have occurred in the time between photography missions.
Our research shows that primary factors controlling storm-induced coastal change include the elevation of the first line of defense, or dune, and the elevation of storm surge and wave runup. Unlike the rapid passage of a typical hurricane, Nor’Ida lasted about 5 days, or 10 tidal cycles, from November 11-15, 2009. The waves and water levels varied a relatively small amount across the long coastal reach that was affected by the storm, providing a unique opportunity to understand the interplay between the lengthy storm duration and pre-storm elevations in determining observed coastal response. Here, we show qualitatively how the coast changed over much of the mid-Atlantic coastline.
Acknowledgement: We would like to thank the Coast Guard Air Station Elizabeth City, NC and pilot Lt. William Coty, Co-Pilot Ltjg Matt Herring, and Flight Mechanic AMT3 Ed Sychora for supporting this overflight aboard HH-60 Helicopter #6017.