GEOMORPHOLOGIC ANALYSIS OF A DRAINAGE BASIN FEEDING THE PROPOSED CONSTRUCTED WETLAND IN SOUTHWESTERN VANDERBURGH COUNTY, IN

The University of Southern Indiana (USI) and the Indiana Department of Transportation (INDoT) are in the planning phase of constructing a wetland on university property in Vanderburgh County, IN. This research reports the quantitative and qualitative characteristics of the watershed that feeds the proposed wetlands. Factors addressed include land use, morphometric parameters, discharge behavior, and sediment transport. Discharge measured during a 0.7” rainfall on 11/16/10 was found to be 0.173 m³/sec at the location furthest downstream. Suspended sediment in the trunk stream was measured and calculated to be 16,441.92 Kg/Day. Bedload sediment mobilized by the 11/16/10 event was found to have an average grain size of 1.65 Phi (medium sand) at the upstream location and 1.36 Phi (medium sand) at the downstream location. Total volumes of sediment recovered were 430g and approximately 2.1kg respectively. The suspended sediment appeared to be silt sized. These results are not unexpected when source terrain is considered. The trunk stream dissects and erodes the loess-mantled Inglefield sandstone that is dominated by silt (loess) and medium grained sand. Although calculated suspended sediment totals per day are substantial, the precipitation event was not large and the stream did not achieve bankfull conditions. Larger rainfalls as well as land use practices will influence the sediment load and discharge of the stream. An accurate record of pre-construction basin characteristics and stream behavior will facilitate planning of the wetland, and provide future researchers a baseline for assessing potential changes to the area.