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ABSTRACT By altering hydrological and geomorphological processes at watershed scales, humans have substantially influenced the movement of sediment on Earth's surface. Despite widespread recognition of human impacts on erosion and deposition, few studies have assessed the magnitude of change in watershed‐scale sediment fluxes before and after the implementation of industrial agriculture and how agricultural development has altered the spatial distribution of sediment fluxes throughout watersheds. This study uses a modeling approach to explore changes in sediment fluxes before and after agricultural development in the upper Sangamon River Basin—an agricultural watershed in the midwestern United States. Comparison of model predictions with river hydrological and sediment data and with information on soil erosion and floodplain sedimentation shows the model accurately captures contemporary fluxes of water and sediment. To assess human impact, native land‐cover conditions are used to estimate the magnitude and spatial distribution of sediment fluxes before the landscape was transformed by farming practices. Results suggest that sediment delivery from hillslopes to streams in this low relief watershed has increased 11‐fold and the sediment load in streams has increased eight‐fold since European settlement. Floodplain sedimentation has also increased dramatically, a finding consistent with recent estimates of post‐settlement alluvium accumulation rates. The proportion of sediment exported from the basin is now slightly greater than it was in the 1800s. Overall, the model results indicate that humans have greatly enhanced the movement and storage of sediment within the upper Sangamon River basin.
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This content will become publicly available on June 5, 2026
Evaluating Change in the Prevalence of River Anabranching Before and After Agricultural Development in the Upper Midwest, United States
Recent research has indicated that numerous lowland rivers in North America and Europe had multithread, anabranching channel patterns prior to widespread human modification of landscapes and that contemporary human activities have transformed many anabranching rivers into single-channel meandering rivers. Although lowland rivers in the upper midwestern United States are predominantly meandering, anabranching occurs locally. Whether anabranching of these river systems was uncommon in the past or intensive agriculture has resulted in near eradication of anabranching channel patterns remains uncertain. This article quantifies the prevalence of river anabranching within several watersheds in the upper midwestern United States prior to widespread European settlement in the early to mid-1800s based on General Land Office survey plat maps and field notes. It also compares this prevalence to the contemporary occurrence of river anabranching. Results show that anabranching reaches were somewhat more common historically (22 percent more reaches in the past compared to the present), but were still relatively rare, constituting only about 1 percent of the total length of streams in the study watersheds. Analysis of the geographic distribution of anabranching reaches reveals that historical spatial patterns generally are different than modern patterns. Thus, only a handful of historical anabranching reaches have persisted through time to the present. The findings place contemporary river anabranching in the upper midwestern United States within the context of past conditions and suggest that human modification of landscapes throughout this region has not substantially modified channel patterns of rivers.
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- Award ID(s):
- 2012850
- PAR ID:
- 10630771
- Editor(s):
- NA
- Publisher / Repository:
- Taylor and Francis
- Date Published:
- Journal Name:
- Annals of the American Association of Geographers
- ISSN:
- 2469-4452
- Page Range / eLocation ID:
- 1 to 18
- Subject(s) / Keyword(s):
- anabranching, fluvial geomorphology, General Land Office surveys, human impact, upper midwestern United States.
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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