| Summary: | The ravine networks in southern Minnesota are facing significant hillslope erosion because of large volumes of water draining from agricultural fields. The fields capture water from rain storms which then drain into drainage tile. Many drain tile systems outlet at the top of ravines, leading to fluvial erosion in concentrated areas. The hillslopes are made of loosely consolidated glacial till that had been deposited by the Des Moines lobe of the Laurentide ice sheet. So, the sediment that is being eroded from the slopes ranges from clay to sand and gravel. When the sediment becomes saturated it may become unstable, resulting in landslides. To mitigate the problem, I designed an infiltration basin for a typical farm that would reduce surface water draining into ravines. I used Quaternary Stratigraphy maps to analyze the till matrix and determined the hydraulic conductivity to determine whether it would be feasible to create an infiltration basin further away from the ravines. The basin can collect and infiltrate the rain water from a 200-acre plot of land because of the till’s moderate hydraulic conductivity. Drainage tile would drain water into the infiltration basin rather than into the ravines. In this study, I calculated that an infiltration basin with dimensions of 590ft x 590ft x 7.5ft would have a discharge rate (to the groundwater) of 789,000 cubic feet/day. The size of the infiltration basin would hold a 3.6-inch rain storm over a 200-acre plot of land and it would empty in 3.5 days. The infiltration basin would take the large amounts of extra water out of the eroding ravines and send it into the groundwater, where it may other recharge deeper aquifers or eventually flow into the Minnesota River.
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