These data are bathymetry (river bottom elevation) and depth-averaged velocities generated from the September 17–18, 2020, survey of the Kentucky Dam tailwater from just downstream from Kentucky Dam to approximately 1,500 feet upstream from the I-24 bridge (about 1 mile total length). Bathymetry and velocity data were collected using an acoustic Doppler current profiler (ADCP) with an integrated global navigation satellite system (GNSS) smart antenna with submeter accuracy. The ADCP and GNSS antenna were mounted on a marine survey vessel, and data were collected as the survey vessel traversed the tailwater along planned survey lines. There was typically one reciprocal pair (two passes) of data collected per line. There was a total of 53 survey lines equally spaced 100 feet apart and oriented approximately perpendicular to the primary flow direction. Data collection software integrated and stored the depth, velocity, and position data from the ADCP and GNSS antenna in real time. Data processing required computer software to extract the bathymetric data from the raw data files and to summarize and map the information. Water-surface elevations were measured at each planned line throughout the survey area with a survey-grade integrated GNSS system with real-time kinematic (RTK) observations in order to convert measured bathymetric depths to elevations referenced to NAVD 88. RTK observations were made using the Kentucky Continually Operating Reference System (KYCORS) network operated by the Kentucky Transportation Cabinet. Data were processed using the Velocity Mapping Toolbox (Parsons and others, 2013) to derive temporally- and spatially-averaged water velocity values. The surveys were conducted during steady discharge conditions from the hydropower turbines at Kentucky Dam. These data were collected to understand flow patterns in the Kentucky Dam tailwater during different discharge conditions from the hydropower turbines at Kentucky Dam and may be used to assist in invasive carp capture and control programs.