Using Recreation-Grade Side-Imaging Sonar to Produce Classified Maps of Submerged Aquatic Vegetation

Understanding the habitat characteristics of aquatic systems is a fundamental tool in fisheries management.  The relative low-cost and availability of recreation-grade side-imaging sonar systems has made capturing high resolution (<10 cm) underwater imagery practical.  Using Humminbird® Side Imaging® sonar and a boat mounted transducer; we evaluated our ability to produce classified maps of submerged aquatic vegetation (SAV) within three Texas reservoirs.  Sonar recordings of littoral habitat were collected and processed into georeferenced mosaic images using SonarTRX© side-scan sonar software.  Resulting GIS layers were interpreted to identify and map SAV, and a classification scheme was developed for each reservoir.  We mapped 298 total hectares of SAV in the three reservoirs, and defined classes by individual species or species groups in mixed vegetation stands.  Area estimates for eleven of twelve classes fell within 95% confidence intervals estimated from concurrent point intercept surveys.  Point intercept data was also used to develop a traditional error matrix providing accuracy assessment for each classified map.  Overall classification accuracy ranged from 78 to 88% for the three reservoirs.  Methods developed demonstrate an accurate and cost effective procedure to calculate SAV coverage and produce a high quality map product.