EFFECTS OF CHANNEL MORPHOLOGY ON FLOODPLAIN INUNDATION AND SURFACE-GROUNDWATER INTERACTIONS IN AN URBAN WATERSHED

Abstract

The purpose of this study is to evaluate groundwater-surfacewater interactions between a stream and the adjacent floodplain. The study site includes two reaches on Paint Branch Creek: an incised reach with inset gravel bars and a non-incised reach with active accretion of gravels bars onto the floodplain and off channel features. Topography, sediment grain size and hydraulic conductivity, groundwater head, and floodplain/channel characteristics were measured. Groundwater head data in gravel bars and adjacent floodplains were monitored for one year to determine seasonal variations in groundwater flow directions, rates, and to develop groundwater probability curves. Identification of groundwater-surfacewater interactions and off channel features roles was determined. In the reach with attached gravel bars, water flows from the creek into the adjacent gravel bars for the most of the year. Evapotranspiration and tropical storms influence seasonal reversals in flow directions between the gravel bar and the floodplain.