| As part of cooperative research between USGS, NASA, and USACE, three airborne lidar surveys have been conducted of North Captiva Island, FL. Three-dimensional lidar topography and bathymetry are shown below of the island area that breached during Hurricane Charley. The two earlier lidar surveys show elevations of the island and vegetation canopy, consisting of pine trees and mangroves, prior to impact. In the last survey, conducted a few days after Charley's landfall using NASA's EAARL, the data have been processed to expose bare earth (i.e. the vegetation and shallow water have been removed from the island and immediately surrounding sea).
| 2004 Breach at North Captiva Island |
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| North Captiva Island: The top photograph was taken by the USGS on August 15, 2004. The first lidar data set was acquired during September 1998 using NASA's ATM (Airborne Topographic Mapper). The second lidar data set was acquired on May 24, 2004 using USACE's CHARTS (Compact Hydrographic Airborne Rapid Total Survey). The third lidar data set was acquired on August 16, 2004 after Hurricane Charley's landfall using NASA's EAARL (Experimental Airborne Advanced Research Lidar) and was processed to remove the vegetation. [larger version] |
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The 1998 lidar topography shows a continuous barrier island. During 2001, Tropical Storm Gabrielle cut two small passes through the island. The May 2004 lidar survey shows where the two small breaches occurred and that the breaches had filled with sand. The August 2004 EAARL survey shows the development of the large Charley breach.
The EAARL data have been further processed to reveal bathymetry of the large breach and where sand was transported from the island and into Pine Island Sound. This capability of acquiring topography and bathymetry seemlessly across the shoreline, with no loss of bathymetric data in very shallow water, is unique to the experimental EAARL sensor. These data are critical in defining the quantity and distribution of sand that was transported landward, as well as defining the geometry of the new pass so that it can be monitored as it fills with sand.
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