High resolution acoustic characterization and change detection to evaluate hurricane effects on a coastal bay bottom

Abstract

Using high-resolution acoustics (sidescan sonar, chirp sonar subbottom, and echo sounder profile data) the shallow surface and subsurface of Sister Lake (Terrebonne Basin) of coastal Louisiana’s deltaic plain was imaged pre- and post-hurricanes Katrina and Rita. The pre-hurricanes survey in May 2005 imaged the entire lake bottom. To assess the effects of hurricanes Katrina and Rita, a second survey in October 2005 included acoustic resurveying of corridors of data covering all major sectors of the lake. Regions of sidescan reflectance differences between pre- and post-storm periods, corroborated with regions of onlapping sediment or zones of scour in the chirp sonar subbottom data, show areas both of sedimentation and erosion between surveys. Ground truth box cores were collected to calibrate acoustic data. Preliminary image processing results of the georeferenced pre- and post-storms sidescan datasets indicate 60% of the area experienced sedimentation and 40% was scoured between surveys. Amplitude reflectivity of chirp horizons were mapped, and incorporated with sidescan amplitude and texture attributes in change detection analysis. Standardized digital processing, supervised classification, and change detection techniques are developed to characterize the bay bottom and shallow subsurface and to assess and quantify storm effects. [Work supported by NOAA NA03NMF4520316.]