SHORT-TERM STUDY OF THE IMPACT OF LAND USE ON CREEK DEVELOPMENT IN PLUM CREEK, OBERLIN OH

Fallout radionuclide fingerprinting, grain size and channel shape are tools used to provide a snapshot into the erosional patterns of an area, such as channel evolution and sediment source. In watersheds that are dominated by agriculture and human development, these tools provide insight into the effects of human activity on these processes. This study determines the influence of upstream land use on changes in source material, using repeat surveys and short lived FRN data to determine erosional patterns, channel geometry, grain size and deposition over the course of a year. The study focuses on the agriculturally dominated watershed of Plum Creek in Oberlin, Ohio. The data provide insight into seasonal variability of isotopes 7Be, 137Cs, and 210Pbex.

The 35.7 km2 watershed consists of agricultural, urban, and forested land in a region with little variability in topography (elevation of 222-­274 m), soil (silty and silty clay loams), or precipitation (mean monthly precipitation is 5.58­-9.91 cm). The variation in the watershed land use includes, from upstream to downstream, an agricultural section, then a golf course, a forested area, and an urban area. We hypothesize that significant agricultural and urban development will increase the magnitude and frequency of the creek’s flow, causing an increase in grain size due to more intense flows, an increase in bankfull depth and channel cross sectional area. This is likely exacerbated by agricultural modifications including drainage tiles. Additionally, we propose that the variation in land use will cause spatial and temporal variation in sediment source and deposition.

From upstream to downstream we observe a decrease in grain size and an increase in channel depth, width and cross-sectional area. There is a noticeable increase in bankfull depth, suggesting that incision is occuring in the creek. The incision may be due to increased runoff from urban and agricultural development in the surrounding area. Isotopic data analyses from detrital in-bed and source sediment are still being completed, and depositional data is being collected. Preliminary data indicate temporal and spatial variation in sediment source. Once completed, these data have the potential to continue to clarify the erosional patterns and impact of land use in a relatively homogenous, small watershed.