These data are a component of a floodplain forest canopy gap dynamics study initiated in 2019 and funded through the US Army Corps of Engineers Upper Mississippi River Restoration, Science Supporting Restoration program. The study included two components: a geospatial component to utilize lidar to identify and map canopy gaps across multiple navigation pools (8, 9, 13, 21, 24, 26 (through Maple Island just south of Lock and Dam 26), and the lower 32 miles of the Illinois River from its confluence with the Mississippi River to Kampsville, IL) within the Upper Mississippi River floodplain and a field component to characterize vegetation in a small subset of the remotely sensed gaps. This layer provides lidar derived polygons the subset of gaps that were selected for field surveys in 2020. Gaps were selected based on a randomly stratified sample of the lidar derived gaps, with stratification occurring based on gap size (small (0.0406-0.1012 ha), medium (0.1013-0.3035 ha), large (0.3036-0.8093 ha)) and annual days of flooding within the gap (low (0.1-20 days), moderate (20.1 - 40 days), high (40.1 - 100 days)). The objective of the field study was to determine whether gaps over varying sizes and flood regimes showed variation in vegetation dynamics within the gaps. The geospatial data and scripts used for initial gap identification are available at: https://doi.org/10.5066/P9BLTSTZ. Floodplain inundation rasters that were used to derive the annual inundation rates are available at: https://doi.org/10.5066/F7VD6XRT.