We take advantage of six fan deposits spread throughout the LSRB to determine the fluvial response of upland agricultural land conversion on steep first-order drainages. Establishing a post-settlement chronology is difficult in the highly erosive knickzone of the Le Sueur. Ravines, first-order channels that link low-gradient uplands with the deeply-incised channel network, experienced changes in erosion rates over time from both impacts, with the erosional history preserved in alluvial fans at the mouths of ravines where they terminate on fluvial terraces. Onto this template of on-going incision, Euro-American land clearing and drainage of previously stable upland prairie and wetlands in the mid-1800s further increased erosion rates in the basin. Seventy meters of base-level drop at the end of the last glaciation initiated millennia of incision that continues on the LSRB today. Ravine alluvial fans in the Le Sueur River Basin (LSRB) of south-central Minnesota record post-glacial Holocene changes and modern anthropogenic disturbances to land cover and hydrology in high-latitude watersheds.
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