These data are high-resolution bathymetry (riverbed elevation) in ASCII XYZ format, generated from the June 5, 2017, hydrographic survey of the Gasconade River near structure A1411 on Missouri State Highway 89 near Rich Fountain, Missouri, to help identify possible effects from extreme flooding on May 1-2, 2017. Hydrographic 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 along planned survey lines distributed throughout the reach. 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. First posted October 3, 2017 Revised May 15, 2019, ver. 2.0