STREAM ENERGY IMPACTING SEDIMENT TRANSPORT THROUGH LOW-GRADIENT AGRICULTURAL STREAMS

Sediment transport carries implications for surface water quality, and too much sediment can reduce available supplies for human use and will degrade ecosystems. In low-gradient, agriculturally dominated stream systems that run through glacial till deposits, sediment flux pathways can be largely influenced by anthropogenic channel modifications. Within McLean County, IL, there are two streams that feed into the two drinking water reservoirs, Lake Bloomington and Evergreen Lake. Parts of these streams have been modified, while other sections have remained natural, as determined based on the degree of sinuosity. In this study, two sections along Six Mile Creek (Lake Bloomington) and two along Money Creek (Evergreen Lake) were sampled biweekly for stream discharge, bedload, and suspended sediment concentrations. The stream sections differ based on if they are natural channels or have been modified, which impacts the stream energy available to mobilize sediment and shape the channels. In the lab, bedload samples were sieved and suspended sediment filtered and dried. Pressure tranduscer data were analyzed to determine a sediment discharge rate along with a stream power curve to compare the modified and unmodified sections of the streams. This project carries implications for how the City of Bloomington monitors and addresses channel morphology issues. If successful, this study will show that channel modification change the flux of sediments through the system, potentially increasing the sediment transport into the two drinking water reservoirs and limiting the freshwater supply for human consumption.