SHORT-TERM AND LOCAL VARIATION OF SEDIMENT SOURCING IN PLUM CREEK, OBERLIN, OHIO

Factors such as surrounding land use can cause variations in erosion patterns and creek development within a watershed. This study focuses on Plum Creek, in Oberlin, Ohio, a 35.7 km² watershed with upstream to downstream farmland, golf course, forested, and urban land use. The watershed has little variability in topography (elevation of 222-­274 m), soil (silty and silty clay loams), or precipitation (mean annual is ~9.6 cm yr^-1 across all sites). We hypothesize that local land usage can alter sediment sourcing within a watershed and cause both spatial and temporal variation. We collected fluvial channel-bed sediment samples at four sites along a ~3 km reach of Plum Creek every two weeks for a year. We also collected potential source samples from different land use types adjacent to each sample site. We use ¹³⁷Cs and ²¹⁰Pb_ex concentrations in the detrital sediment to measure the correlation between land use and sediment source. Isotope data indicates significant spatial and temporal variation in source sediment over the year, suggesting that spatial factors, such as surrounding land use, and temporal factors, such as rainfall and climate, can affect sediment sourcing in small watersheds. Our data recontextualizes a single-site, single-instance sampling model, suggesting that sediment sources can change significantly over time and across relatively small distances. Thus, fallout radionuclides provide an intriguing opportunity to understand short-term dynamics in fluvial sediment sourcing.