Through-bank Flooding of Floodplains
Abstract
Floodplain inundation is often assumed to be the result of overbank flow during high flow conditions. However, when surveying levees one can observe that these features may contain breaches that facilitate the exchange of surface water during below bank-full flow conditions. A limited number of studies confirm that these breaches distribute water and particulate matter at greater distances from the main river than overbank flow, but little is known about the difference in time-averaged magnitude of these fluxes and their implications for overall floodplain inundation. This study aims to develop an integrated process-based understanding of controls on fluxes onto the floodplain by overbank flow and by through-bank flow using high-resolution numerical modeling. The study site is the Congaree River and the adjacent floodplain consisting of the Congaree National Park. A natural levee, which is breached at multiple locations by both permanent and ephemeral channels, locally separates the main river and the floodplain. Pressure sensors and ADCP's are employed in the river and the floodplain to collect depth and velocity information to calibrate and validate the hydrodynamic model. Initial simulations show good correspondence between observed and modeled water levels. An important observation in the hydrodynamic simulations is that the flux through the levee (below bank-full flow) can lead to substantial and frequent floodplain inundation. This observation has important implications for floodplain hydraulic connectivity, sediment accumulation and nutrient cycling as statistical analyses of discharge reveal that through bank inundations appear to be the dominant material exchange process.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMEP52C..19V
- Keywords:
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- 1803 Anthropogenic effects;
- HYDROLOGYDE: 1825 Geomorphology: fluvial;
- HYDROLOGYDE: 1847 Modeling;
- HYDROLOGYDE: 1856 River channels;
- HYDROLOGY