This dataset contains cross-section geometry and sediment-size data collected in the fall of 2019 from Muddy Creek and North Fork Gunnison River below Paonia Reservoir, western Colorado. Six cross sections were surveyed using Real-Time Kinematic Global Navigation Satellite System (RTK-GNSS) methods to document channel geometry below Paonia Reservoir. One cross section was surveyed on Muddy Creek below Paonia Reservoir, and five cross sections were surveyed from North Fork Gunnison River below Paonia Reservoir. All six cross sections are incorporated in this data release within one shapefile. Pebble counts were performed at each of the six cross sections to document sediment-size downstream from the reservoir. Four transects were completed at each cross section, where sediment size was measured and recorded. Sediment-size data are presented in .CSV files, with one file for each cross-section location, incorporating all of the data for each of the four transects at that location.