Combining Em and Lidar To Map Coastal Wetlands: An Example From Mustang Island, Texas

We combined airborne lidar and ground-based EM induction measurements with vegetation surveys along<br>two transects across Mustang Island, a barrier island on the Texas coast, to examine whether these methods can<br>be used to map coastal wetlands and associated geomorphic environments.<br>Conductivity varied inversely with elevation along both transects. Elevation and conductivity profiles correlated<br>reasonably well with habitat mapped in the largely imagery-based 1992 National Wetland Inventory (NWI),<br>but they possessed greater detail and identified misclassified habitat. Detail achievable with elevation and conductivity<br>data was similar to that achieved in on-the-ground vegetation surveys. Lowest elevations and highest conductivities<br>were measured in saline environments (marine and estuarine units, forebeach, salt marsh, and wind-tidal<br>flats). Highest elevations and lowest conductivities were measured in nonsaline environments (upland and palustrine<br>units, dunes, vegetated-barrier flats, and fresh marsh).<br>Elevation and conductivity data allow better discrimination among coastal wetland and geomorphic environments<br>than can be achieved from image interpretation alone. Future work should include evaluating the effect of<br>vegetation density on lidar-beam penetration, quantifying seasonal change in ground conductivity in fresh and saline<br>coastal environments, examining the geographic variability of elevation and conductivity statistics, and evaluating<br>the use of airborne EM sensors to measure ground conductivity at multiple exploration depths.