Improved Operational Efficiency of Topo-Bathymetric LiDAR Surveys Using Real-time Water Clarity Sensors
The coastal zone is a challenging place to map but topo-bathymetric lidar sensors such as the Leica Chiroptera II system is well suited to survey this land-sea boundary and provide seamless elevation across this boundary. In addition to collecting the elevation at high resolution ~ 1m and vertical precision ~ 15 cm, the intensity of the reflected green laser also provides insights into what is on the seabed and when combined with other topographic metrics and the RCD30 RGB and NIR camera, that is coupled with the lidar, can be used to derive benthic cover maps of the nearshore. The ability of the green laser to penetrate the water column is a function of water clarity and thus surveys require a turbidity management approach to optimize when and where to fly the sensor successfully. In addition to monitoring the weather, mostly wind speed and direction, fog and rainfall, we deploy buoys equipped with real-time turbidity sensors to allow the nearshore water clarity conditions to be determined prior to flights. The buoys and moorings are small enough to be relocatable to provide real-time turbidity measurements in a variety of study sites during the lidar survey campaign, thus improving our operational efficiency. The turbidity management approach will be presented along with the results of several coastal lidar surveys that have been used for identifying nautical hazards, mapping submerged aquatic vegetation (eg. Seagrass), input to hydrodynamic model simulations, and shoreline sensitivity mapping for contaminant spill preparedness.