Abstract

Little is known about the historic planform channel change of the Minnesota River of south-central Minnesota, USA. This is despite research that demonstrates anthropogenic activities have altered the Minnesota River Basin's hydrology, land use, and climate. In addition, the threat of invasive carp infestation requires an understanding of Minnesota River planform change to assess mitigation strategies. This thesis focuses on the lower Minnesota River (LMR) by measuring planform channel change (lateral channel migration, width, and sinuosity) from 1937 to 2013. Analysis is conducted by utilizing remote/GIS analysis of historic aerial photographs. A secondary focus addresses and quantifies the inherent/introduced error/uncertainly within remote analysis in channel planform studies. Error in image referencing and channel digitization were quantified and applied to planform measurements throughout the LMR, as opposed to spatially uniform or borrowed values utilized in past literature. The results reveal the LMR exhibits an average increase in channel migration from ~0.77 meters per year (m/y) during the 1937-1951 interval to ~0.99 m/y during the 1980-1991 interval. Despite a decrease in lateral migration observed between the 1980-1991 and 1991-2013 intervals (~0.17 m/y decrease), the highest observed maximum migration rates are in these two recent intervals, with the most significant lateral migration (~16 m/y) in the 1980-1991 interval. Average channel width increased from ~70 m to ~113 m from 1937 to 2013. Sinuosity has decreased associated with a decrease in stream length from 180 km to 167 km from 1937 to 2013. These Planform changes are interpreted as a result of anthropogenic induced alteration in the MRB's hydrology, impacting processes that control channel behavior. Beyond spatially averaged temporal trends, spatial variability of measured planform characteristics within the LMR correlate with locations where: 1) anthropogenic structures control river behavior (low rates of planform change), 2) distinct valley segments identified as sediment sinks in low gradient reaches (high rates of planform change), and 3) major tributary systems enter the LMR (increase in lateral migration downstream from the confluence). Given ongoing historic change observed here and the underfit nature of the LMR, we believe this work demonstrates a substantial challenge to any invasive carp mitigation strategy.

Advisor

Phillip Larson

First Committee Member

Patrick Belmont

Second Committee Member

Woo Jang

Third Committee Member

Cynthia Miller

Date of Degree

2018

Language

english

Document Type

Thesis

Degree

Master of Science (MS)

Department

Geography

College

Social and Behavioral Sciences

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

Available for download on Wednesday, June 05, 2019

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