As the aircraft flies along the coast, a laser altimeter scans a several hundred meter swath of the earth's surface acquiring an estimate of ground elevation every few square meters. Change is quantified by comparing pre-storm to post-storm surveys. Traditional USGS topographic sheets do not have sufficient resolution to be useful for comparing coastal elevations. Airborne scanning laser surveys are providing unprecedented data to investigate the magnitude and causes of coastal changes that occur during severe storms.

The ALACE Project

The Airborne LIDAR Assessment of Coastal Erosion (ALACE) project, a predecessor of the Topographic Change Mapping project, has been collecting baseline coastal topographic data for the continental U.S. since 1996. The data collected are being used to determine coastal topography and elevation, which can be used to study coastal processes such as erosion, storm damage, inlet migration, beach nourishment, and shoreline stabilization.

LIDAR coverage to date (September 1996 to October 2000) for the Conterminous U.S. The bold red line indicates the survey flight lines (Source: USGS)

The acquisition of baseline coastal topographic data primarily occurs during the fall, when the beach generally is at its widest due to sand accumulation over the summer months, and prior to winter erosion. However, research missions are also conducted at other times to study the impacts on coastal regions of weather phenomena such as El Niño or hurricanes. All flights are timed to coincide with low tide, when the beach is most exposed.

For information on LIDAR data availability please see http://www.csc.noaa.gov/crs/tcm/data_avail.html

See also the LDART data retrival tool
http://www.csc.noaa.gov/cgi-bin/crs/tcm/ldart_start.pl

Other resources and information of interest can be found at the NOAAS Coastal Services Center - http://www.csc.noaa.gov/