Predicting stream channel erosion in the lacustrine core of the upper Nemadji River, Minnesota (USA) using stream geomorphology metrics |
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| Authors: | Joseph A Magner Kenneth N Brooks |
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| Institution: | (1) Minnesota Pollution Control Agency, 520 Lafayette Road, St Paul, MN 55155, USA;(2) Department of Forest Resources, University of Minnesota, 1530 Cleveland Avenue, St Paul, MN 55108, USA |
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| Abstract: | The USA Clean Water Act requires the development of a total maximum daily load (TMDL) when Minnesota’s water quality standard
for turbidity is exceeded; however, regions underlain with fine-grained lacustrine deposits yield large natural background
loads of suspended inorganic sediment. A review of hydrogeologic pathways was conducted along with the statistical analysis
of geomorphic metrics, collected at 15 sites with varying drainage areas in the upper Nemadji River basin, northeastern Minnesota.
Regression analysis indicated a strong linkage between bankfull cross-sectional area and drainage area. Dimensionless geomorphic
metric ratios were developed to predict channel evolution potential and associated channel erosion risk. Sites located in
drainage areas less than 2 km2 had low erosion risk and showed a correlation between channel slope and relative roughness (D
84/mean bankfull channel depth, 88%). A principal components analysis explained over 98% of the variance between sites and indicated
five important channel shape metrics to predict channel erosion: bankfull width, bankfull depth, maximum depth, cross-sectional
area, and valley beltwidth. Mass wasting of cohesive stream channel sediment was influenced by groundwater discharge and produced
turbid waters in the upper Nemadji River. |
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| Keywords: | Erosion risk Cohesive-sediment Channel stability Turbidity and water quality |
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