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Geomorphic evolution of the Le Sueur River, Minnesota, USA, and implications for current sediment loading

Special Paper of the Geological Society of America

By:
, , , , , , and
DOI: 10.1130/2009.2451(08)

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Abstract

There is clear evidence that the Minnesota River is the major sediment source for Lake Pepin and that the Le Sueur River is a major source to the Minnesota River. Turbidity levels are high enough to require management actions. We take advantage of the well-constrained Holocene history of the Le Sueur basin and use a combination of remote sensing, fi eld, and stream gauge observations to constrain the contributions of different sediment sources to the Le Sueur River. Understanding the type, location, and magnitude of sediment sources is essential for unraveling the Holocene development of the basin as well as for guiding management decisions about investments to reduce sediment loads. Rapid base-level fall at the outlet of the Le Sueur River 11,500 yr B.P. triggered up to 70 m of channel incision at the mouth. Slope-area analyses of river longitudinal profi les show that knickpoints have migrated 30-35 km upstream on all three major branches of the river, eroding 1.2-2.6 ?? 109 Mg of sediment from the lower valleys in the process. The knick zones separate the basin into an upper watershed, receiving sediment primarily from uplands and streambanks, and a lower, incised zone, which receives additional sediment from high bluffs and ravines. Stream gauges installed above and below knick zones show dramatic increases in sediment loading above that expected from increases in drainage area, indicating substantial inputs from bluffs and ravines.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Geomorphic evolution of the Le Sueur River, Minnesota, USA, and implications for current sediment loading
Series title:
Special Paper of the Geological Society of America
DOI:
10.1130/2009.2451(08)
Issue:
451
Year Published:
2009
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Special Paper of the Geological Society of America
First page:
119
Last page:
130