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Volume

2

Issue

1

Abstract

Hydraulic bankfull geometry or regional curves are a useful metric for evaluating stream stability and planning stream restoration projects. Streams and tributaries within the Middle Pee Dee River Basin (MPDRB) in South Carolina drain an agrarian and forested landscape characterized by water conveyance structures, such as active and historical ditches which support forestry and agriculture. While streams in the region are generally stable, pockets of this landscape are beginning to face increasing pressure from development with signs of stream instability apparent in several locations as evidenced by streams in and around the urbanizing areas around Darlington and Florence, SC. In order to provide a foundation for potential stream restoration projects in the area, 15 sites in the MPDRB were selected on the basis of catchment area, in categories of small (km2), small-medium (50-500 km2), medium (500-1000 km2), and large (>1000 km2). Bankfull geometries, channel substrate, flow and water temperature were measured at all the sites and a set of regional hydraulic geometry curves developed. The frequency of bankfull flows that occurred over the period of sampling were also estimated to document floodplain connectivity. Results suggest that bankfull dimensions in the MPDRB were well correlated with bankfull discharge and drainage area. The results showed that hydraulic geometry in the region were similar to those measured in a similar physiographic region in North Carolina. The study also shows that streams in the MPDRB experience bankfull exceeding flows much more frequently than streams in other parts of the country, but at a frequency that is comparable to streams in the coastal plains of North Carolina.

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