Use of High-Resolution Topo-Bathymetry to Assess Shoreline Topography and Future Development of a Slackwater Harbor near Dardanelle, Arkansas, October 2021

The U.S. Army Corps of Engineers - Little Rock District (SWL) Civil Works program has a mission to maintain cohesion between physical and naturally developed environments. Evaluation of shoreline stability and adjacent development of a harbor along the McClellan-Kerr Arkansas River Navigation System at River Mile 202.6 is essential in establishing a baseline for potential impacts and future monitoring of the proposed harbor. A combination of multibeam sonar and high-resolution, low-altitude aerial light detection and ranging (lidar) data were used to provide data and analysis needed for as-built information and future monitoring of river shoreline and floodplain management and maintenance. In October 2021, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers, completed high-resolution bathymetric (underwater elevation) and topographic surveys of the Arkansas River and a quarry at the proposed slackwater harbor near Dardanelle, Arkansas. 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. Data were collected as the vessel traversed the river and quarry along overlapping survey lines distributed throughout the areas. Data collection software integrated and stored the depth data from the MBES and the horizontal and vertical position and attitude data of the vessel from the INS in real time. Data processing required computer software to extract bathymetry data from the raw data files and to summarize and map the information. Topographic data were collected as a lidar point cloud (LPC) using an Unmanned Aircraft System (UAS) with a Yellowscan VX20-100 lidar payload, which consists of the lidar scanner and an INS. The LPC data were collected as the UAS followed two perpendicular transects orientations (north-south and east-west) on separate flights. The LPC was corrected using a post-processed kinematic (PPK) solution with a Trimble R8s base station, and ground control points (GCPs) surveyed using Propeller AeroPoint smart targets which were PPK corrected to a nearby continuously operated reference station (CORS) tower. The LPC was attributed to the American Society for Photogrammetry and Remote Sensing (ASPRS) point classification standards. The LPC was colorized from a UAS-collected red-green-blue (RGB) orthoimage collected using a Ricoh GR camera. The processed bathymetric datasets and the UAS lidar dataset are provided in the ASPRS LAS format with associated metadata files in the zipped archive named SlackwaterHarbor_DardanelleAR_2021-10_data.zip. The LAS format is a standardized binary format for storing 3-dimensional point cloud data and point attributes along with header information and variable length records specific to the data. Data points are stored as a 3-dimensional data cloud as a series of x (longitude), y (latitude) and z (elevation) points. Please refer to http://www.asprs.org/Committee-General/LASer-LAS-File-Format-Exchange-A… for additional information. Topographic data outside of the area collected by the UAS were extracted from aerial lidar data collected in 2014, publicly available from the USGS National Elevation Dataset (NED) at https://prd-tnm.s3.amazonaws.com/LidarExplorer/index.html#/. The two bathymetric datasets, the ground points from the UAS lidar data thinned to a 1.64-foot (0.5-meter) resolution, and the public lidar data were combined to create a multisource point cloud of the ground in the proposed harbor area and surroundings. The multisource point cloud dataset is provided in ESRI Shapefile format (ESRI, 2021) with an attribute table and metadata in the zipped archive named SlackwaterHarbor_DardanelleAR_2021-10_Multisource_data.zip. Attribute/column labels of this table are described in the "Entity and attribute" section of the associated metadata file. The multisource point cloud was used to generate an ESRI ASCII grid (ESRI, 2021) with metadata in the zipped archive named SlackwaterHarbor_DardanelleAR_2021-10_Multisource_grid.zip. References Cited: Environmental Systems Research Institute, 2021, ArcGIS: accessed May 20, 2021, at http://www.esri.com/software/arcgis/.