title: Large shift in source of fine sediment in the upper Mississippi river.
abstract: Although sediment is a natural constituent of rivers, excess loading to rivers and streams is a leading cause of impairment and biodiversity loss. Remedial actions require identification of the sources and mechanisms of sediment supply. This task is complicated by the scale and complexity of large watersheds as well as changes in climate and land use that alter the drivers of sediment supply. Previous studies in Lake Pepin, a natural lake on the Mississippi River, indicate that sediment supply to the lake has increased 10-fold over the past 150 years. Herein we combine geochemical fingerprinting and a suite of geomorphic change detection techniques with a sediment mass balance for a tributary watershed to demonstrate that, although the sediment loading remains very large, the dominant source of sediment has shifted from agricultural soil erosion to accelerated erosion of stream banks and bluffs, driven by increased river discharge. Such hydrologic amplification of natural erosion processes calls for a new approach to watershed sediment modeling that explicitly accounts for channel and floodplain dynamics that amplify or dampen landscape processes. Further, this finding illustrates a new challenge in remediating nonpoint sediment pollution and indicates that management efforts must expand from soil erosion to factors contributing to increased water runoff.
authors: Department of Watershed Science, Utah State University, Logan, Utah 84332, USA. patrick.belmont@usu.edu
authors: Patrick
authors: P
authors: Belmont
authors: Karen B
authors: KB
authors: Gran
authors: Shawn P
authors: SP
authors: Schottler
authors: Peter R
authors: PR
authors: Wilcock
authors: Stephanie S
authors: SS
authors: Day
authors: Carrie
authors: C
authors: Jennings
authors: J Wesley
authors: JW
authors: Lauer
authors: Enrica
authors: E
authors: Viparelli
authors: Jane K
authors: JK
authors: Willenbring
authors: Daniel R
authors: DR
authors: Engstrom
authors: Gary
authors: G
authors: Parker
mesh_terms: D019015:Geologic Sediments / Q000032:analysis*; D045483:Rivers; D014481:United States