Analysis of historic orthomosaic imagery collected through various agencies for mapping active channel and floodplain changes along a 22.5-km reach of the Green River at Gray Canyon near Green River, Utah from 1938-2021: shapefiles

The U.S. Geological Survey mapped and analyzed historical imagery along the Green River in Gray Canyon, Utah from 1938 to 2021. To improve our understanding between flows and the channel in our study reach, we digitize the active channel and floodplain boundaries of the river for each available image from 1938 to 2021, then calculate the amount of channel change occurring throughout the reach between each set of years. We utilize Soil Conservation Service Scan (SCS), National Agriculture Imagery Program (NAIP), High Resolution Orthoimagery (HRO), and Worldview 2 & 3 aerial imagery to create a historical timelapse of our study area. We calculate both the floodplain formation and floodplain destruction between years. Overall, the rate of floodplain formation has increased in recent years, indicated by an encroachment of vegetation into the active channel on both the mid-channel islands and along the banks. The active channel area in our reach has been decreasing since the mid-1970s.