Application of Recreational-Grade, Side-Scan Sonar to Map Substrate in a Shallow, Intermittently-Navigable Stream

Since 1997, the Division of Wildlife has stocked more than 610,000 yearling Brown Trout Salmo trutta into three program streams in Ohio.  In an effort to provide better understanding of the habitats that provide adequate Brown Trout habitat, we quantified substrate in Clear Creek, one of the program streams.  We conducted these surveys on three dates in spring 2011 (discharge > 16.9 cubic m/s) using a recreational-grade side-scan sonar unit (Humminbird 1198c, Johnson Outdoors, Inc., Racine, WI, USA) and collected 475 georeferenced, overlapping images representing nearly 10 river miles and 300,000 square meters of substrate.  Mean depth was extremely shallow at the location of each image, averaging 1.2 m (+/− 0.4 m, standard deviation; range 0.5–4.1 m), which likely limited map accuracy (overall accuracy with nine classes = 54%).  Consolidating similar substrate classes (i.e., rocky fines and sand into “fines”) increased accuracy (71% with consolidated classes).  Our approach illustrates the potential to map a large amount of substrate in a short time period with reasonable accuracy in a relatively shallow stream using recreational-grade, side-scan sonar.