Bathymetric and supporting data for estimation of reservoir storage capacity and geomorphic change detection analysis from a multibeam bathymetric survey of Randy Poynter Lake, Rockdale County, Georgia

Rockdale County Department of Water Resources (RCDWR) has a mission to update estimates of the reservoir storage capacity of Randy Poynter Lake in northern Georgia and to assess recent sedimentation. The U.S. Geological Survey (USGS) Lower Mississippi-Gulf Water Science Center (LMGWSC) collected bathymetric data from November 29, 2022 to December 4, 2022 in support of RCDWR’s mission. Bathymetric data were collected using a high-resolution multibeam echosounder mapping system (MBMS), which consists of a multibeam echosounder (MBES) and an inertial navigation system (INS) mounted on a marine survey vessel, similar to methodologies described by Huizinga (2017). The final dataset of lakebed elevations (RandyPoynter2022_points.shp) is provided in ESRI Shapefile format (ESRI, 1998) as three-dimensional (3D) point feature geometries projected in the Universal Transverse Mercator (UTM) coordinate system, zone 17 north (N), horizontally referenced to the North American Datum of 1983, 2011 realization (NAD83 (2011)) and vertically referenced to the North American Vertical Datum of 1988 (NAVD88) (NGS, 2018b). The shapefile’s attribute table provides an uncertainty estimate for each 3D point in units of meters. Elevations and uncertainties were estimated at a grid spacing of 0.5 meters using the Combined Uncertainty and Bathymetric Estimator (CUBE) algorithm (Calder and Wells, 2007) implemented in HYPACK 2022, a hydrographic collection and post-processing software. The 2022 point dataset of gridded lakebed elevations was combined with additional elevation data outside of the area collected by the MBMS up to the flood pool elevation of about 225.5 meters, or 739.9 feet (Rockdale County, 2013). The supplemental data included topographic bare-earth aerial light detection and ranging (lidar) points collected between 2018 and 2019, publicly available from the USGS 3D Elevation Program (3DEP), as well as topographic bare-earth lidar and single-beam data collected by Lee (2012). The multisource elevation dataset was used to generate a continuous surface up to the flood pool elevation from which topo-bathymetric contours were created at both 2-foot and 0.5-meter intervals. The topographic contours are provided in ESRI Shapefile format with an attribute table and metadata in the zipped archive named RandyPoynter2022_contours.zip.