The Role of Topographic Variability on River-Floodplain Connectivity across Several Floodplains

High-resolution topographic data reveal remarkable variability in floodplain topography. This includes, as expected, oxbows, chute channels, and scroll bars, but unexpectedly this also includes long and interconnected floodplain channels. The role of these floodplain channels is unclear and we suspect that floodplains with long, interconnected floodplain channels have a higher capacity to exchange water between the river channel and floodplain and remove nitrate from floodwaters than those without floodplain channels. In this work, we compare the hydrodynamics on five floodplains with various degrees of topographic variability and river-floodplain connectivity. These river-floodplain systems include the East Fork White River (in two separate reaches) and the Tippecanoe River in Indiana, and the South River and Stroubles Creek in Virginia. We constructed two-dimensional numerical models using 2-D HECRAS of these river-floodplain systems from LiDAR data to investigate floodplain hydrodynamics over a range of flows. Specifically, we quantified the surface-water exchange flux across the river-floodplain boundary and the surface-water residence time of floodwaters on the floodplain. We will discuss the role of topographic variability (quantified via LiDAR data) on river-floodplain connectivity (simulated using 2-D HECRAS) across these river-floodplain systems. This has important implications for floodplain restoration with the goal of enhancing river-floodplain exchange and nitrate removal.