Ground-truthing acoustic side-scan signatures on the upper Ohio River

Sediment samples and bottom imagery were collected at 248 locations on a 40-mile reach of the upper Ohio River (Emsworth, Dashields, Montgomery, and New Cumberland pools) to ground-truth acoustic side-scan sonar signatures, previously collected by the U.S. Army Corps of Engineers during 2009.  We used a 36x28-cm modified VanVeen grab to sample sediment and a digital video system to record substrate imagery.  Using field observations characterizing grab performance, laboratory grain-size analyses, and digital substrate images in combination, we found substantial variation in dominant grain size both among and within river pools.  Samples from Emsworth pool (uppermost of the pools sampled) were almost entirely fine-grained substrates, while New Cumberland pool (the furthest pool downriver) was skewed toward coarse-grained substrates, the latter coinciding with the greatest number of incidental observations of mussels.  Generally, acoustic classes 1-3 were coarse-grained and distinct from classes 4-7, which were fine-grained.  Information generated by this study will be used to calibrate acoustic signatures and increase confidence levels in predicting substrate characteristics for unsampled locations thoughout the study area, enabling us to identify suitable habitats for taxa of interest, quantify the impacts of navigation on habitats and species, and identify potential restoration opportunities within the project area.