Single-beam bathymetric survey of the French Broad River near the Interstate 26 bridge south of Asheville, NC – December 2020, Mid-Construction #1

In January 2020, the North Carolina Department of Transportation (NCDOT) began work on the Interstate 26 (I 26) highway widening project that involves a bridge crossing over the French Broad River (FBR) near Asheville, North Carolina. The U.S Geological Survey (USGS) in cooperation with the NCDOT conducted a pre-construction bathymetric survey of the streambed in June 2019 (Whaling and Wagner, 2021) within a one-kilometer reach of the FBR at the bridge construction site. A canoe-based repeat bathymetric survey was collected with a single-beam echosounder approximately 11 months after construction began, with the purpose to monitor geomorphological changes to the streambed and inform the NCDOT of potential impacts from construction activities. The survey extended from 300 meters (m) upstream to 700 m downstream from the bridge. Depth data were collected using a canoe-mounted CEESCOPE single-beam echosounder manufactured by CEE Hydrosystems. Position and elevation data were collected using an SBG Ellipse-D, a dual antenna Real-Time Kinematic (RTK) Inertial Navigation System (INS). The final dataset provides position data in three dimensions with units of meters supplied in a “XYZ” file.  The data are projected in Universal Transverse Mercator (UTM) coordinate system, zone 17 north, horizontally referenced to the North American Datum of 1983 (NGS, 2018a), 2011 realization (NAD83 2011), and vertically referenced to the North American Vertical Datum of 1988 (NAVD88; NGS, 2018b).