Field measurements of depth-averaged flow velocity were acquired from the Tanana and Nenana Rivers near Nenana, Alaska, August 18, 2021, to support research on estimating surface flow velocities from remotely sensed data via particle image velocimetry (PIV). The velocity measurements included in this data release were obtained using a TRDI RiverRay acoustic Doppler current profiler (ADCP) deployed from a boat with an outboard motor. These data were collected along 7 cross-sections on the Tanana River and 7 cross-sections on the Nenana River; two passes across the channel were made at each cross-section. This data release provides depth-averaged flow velocities derived from the raw ADCP data using the TRDI WinRiver II processing software. The WinRiver II output was imported into the USGS Velocity Mapping Toolbox (VMT), which was used to project measurements made along each pass back and forth across the channel onto a common mean cross-section and smooth the data. VMT and custom MATLAB functions were then used to generate text files with projected spatial coordinates, depth-averaged velocity magnitudes, and east and north components of the velocity vectors. The spatial location of each measurement was obtained using a differential GPS included as part of the RiverRay instrument package. The map projection and datum for these data are UTM Zone 6 N and NAD 83, respectively. This data release consists of two comma-delimited (*.csv) text files, one for the Tanana River and one for the Nenana River. Each file consists of five columns: UTM_East_m, UTM_North_m, Velocity_Magnitude_m_per_s, Velocity_East_Component_m_per_s, and Velocity_North_Component_m_per_s. The first two columns are the easting and northing spatial coordinates, respectively, the third column is the depth-averaged velocity magnitude in meters per second, the fourth column is the east component of the the depth-averaged velocity magnitude in meters per second, and the fifth column is the north component of the the depth-averaged velocity magnitude in meters per second. This field-based data set was used to assess the accuracy of remotely sensed estimates of surface flow velocity derived from fixed wing aircraft-based optical image sequences via PIV.