Before and after 3D topography showing where the barrier island was overtopped by waves and storm surge, Gulf Shores, AL: In the pre-Ivan view, the two rows of rectangular mounds are houses (hotter colors indicate higher elevation) on either side of a road. The laser reflects from the roof of a house just like it would from the ground, hence the houses and infrastructure have become part of the map. Data smoothing, and un-surveyed areas between laser shots, have rounded the edges of the houses. Compare the images to see the loss of houses during Hurricane Ivan. Also note the loss of the protective dune that before the storm was located between the first row of houses and the gulf of Mexico. The pre-Ivan topography was measured with USACE Joint Airborne Lidar Bathymetry Technical Center of Excellence - CHARTS lidar system. The post-Ivan topography was measured with NASA's EAARL.

The topographic surveys shown at the top of the page have been differenced showing vertical change

Changes between the pre- and post-Ivan lidar surveys draped over topography: The topographic surveys shown at the top of this page have been differenced to show vertical change; red indicates a decrease in elevation and green indicates an increase. This vertical change has been draped over the post-Ivan topography. The houses that survived the storm are white, indicating no change. The houses that were destroyed are red, indicating loss of elevation. Note the green area over the center section of road indicating that sand has been deposited by wave overwash.

Before and after Ivan photographs of the area within the rectangle on the lidar images above.

Before and after Ivan photographs of the area within the rectangle drawn on the lidar images above. These are U.S. Geological Survey photographs. [larger version]

View Pre- and Post-Storm 3D Topography:

Index
Map

Breached
Island

Overwashed
Island

Destroyed
Houses

Collapsed
Building

St. Peterburg Science Center > Coastal Change Hazards: Hurricanes and Extreme Storms > Hurricane Ivan

Accessibility FOIA Privacy Policies and Notices

U.S. Department of the Interior | U.S. Geological Survey
URL: http://coastal.er.usgs.gov/hurricanes/ivan/lidar/dune.html
Page Contact Information: Feedback
Page Last Modified: October 20, 2009 @ 04:16 PM (JSS)