Year of Award
Master of Science (MS)
Department or School/College
Department of Geosciences
Johnnie Moore, Lisa Eby
bedload, Blackfoot, channel geometry, Clark Fork, confined, dispersing, DREAM, HEC, hydrology, modeling, Montana, processes, rates, removal, reservoir erosion, sediment budget, sediment characteristics, sediment transport, sediment waves, suspended, thres
University of Montana
Measurements of bedload transport in combination with suspended sediment and discharge data collected by the USGS illustrate the rates, magnitudes and processes by which reservoir sediment evacuated the Milltown Reservoir after the 2008 removal of Milltown Dam from just downstream of the confluence of the Blackfoot and Clark Fork Rivers, Montana. Mobilized sediments transported as a series of distinct waves and the speed at which the waves moved downstream was dependent upon the grain size of the sediment. Sand and smaller sized particles were transported out of the reservoir rapidly both as bedload and in suspension with different thresholds for incipient motion between the confined Blackfoot and unconfined alluvial Clark Fork Arms of the reservoir. Bedload sediments, gravel and larger sized, transported downstream as a dispersing and translating wave. Sediment budget calculations, both volumetric and transport derived, illustrate the one-dimensional HEC-6 and DREAM-1 model’s inaccuracy in predicting sediment transport in unconfined alluvial deposits while both models predicted accurately confined channel geometry transport settings. Results from sampling and modeling demonstrate that the most important factors in reservoir sediment transport are the channel geometry, hydrology, and grain size and location of the reservoir sediment; which in turn determine distance, processes and timing of transport.
Johnsen, James Walden, "SAMPLING AND MODELING OF SEDIMENT TRANSPORT AND RESERVOIR EROSION FOLLOWING DAM REMOVAL: MILLTOWN DAM, MONTANA" (2011). Graduate Student Theses, Dissertations, & Professional Papers. 1334.
© Copyright 2011 James Walden Johnsen