Floodplain flow directions and the origins of floodplain channels
Abstract
Floodplain channels are etched into floodplain surfaces and help maintain floodplain hydraulic connectivity, especially at sub-bankfull conditions of the main river. We analyzed topographically driven flow directions and flow accumulations of Congaree River floodplain (SC) channel systems using a lidar digital elevation model (DEM) and field measurements. The results show: 1) The floodplain has a longitudinal-shaped flood basin formed by the modern Congaree River levee and the northern bluff. Through-bank flow and overland flow from the Congaree River levee may flow into the flood basin where they merge the water from northern upland creeks. 2) High flow accumulations usually occur in floodplain channels, oxbows, and some unchanneled areas. 3) Discharge measurements of selected floodplain channels indicate different water sources entering the floodplain during sub-bankfull conditions, including upland creek, water accumulation on floodplain surface and through-bank flow from the main river. 4) Water level measurements of the main river shows non-linear pattern of through-bank flows and overbank flows at 50 major through-bank channels. Taken together these results show that the flow accumulation approach can explain the formation of upland creeks and some through bank channels. On the other hand, the limitations of the "watershed area" concept and flow accumulation analyses on such low relief and low-gradient likely point out different origins and development processes of for most floodplain channels.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP53G2263T
- Keywords:
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- 1821 Floods;
- HYDROLOGY;
- 1824 Geomorphology: general;
- HYDROLOGY;
- 1862 Sediment transport;
- HYDROLOGY