Effects of fluctuating levels of lake superior on morphological adjustments in the neebing-mcintyre floodway, thunder bay, Ontario Canada

Autor: Brian A. M. Phillips, Harun Rasid
Rok vydání: 1990
Předmět:
Zdroj: Regulated Rivers: Research & Management. 5:111-127
ISSN: 1099-1646
0886-9375
Popis: The Neebing-McIntyre Floodway, a relatively straight, trapezidal flood-control channel, was constructed in 1983 to dispose of the combined flows of the Neebing and the McIntyre rivers into Lake Superior. Because of its location in a transitional fluvial/lacustrine environment, related processes had direct and indirect impacts on its morphological readjustments. During the post-construction period (1983-88) the combined peak flows of the Neebing and the McIntyre rivers never exceeded the two-year design floods for the floodway, resulting in relatively low stream power and sediment transport rates. The average rate of sedimentation in the new channel (1100 m3 y−1) was thus much lower than the designers' estimated volume (11 800 m3 y−1). These low-flow events coincided with high water levels in Lake Superior in 1985-86, reinforcing the normal backwater effect in the floodway and further dampening its stream power. During this event the floodway behaved hydraulically almost like a reservoir, with fluctuating water levels and wind-generated waves as the principal geomorphological agents of bank erosion. Estimates based on volumetric surveys indicate annual rates of bank erosion ranging from 0.03 to 0.16 m3 m−1 of bank length, with an average annual rate of 0.1 m3 m−1. The bank materials are composed of highly erodible sandy loam and loamy sand, which have a tendency to disperse and liquefy relatively easily. There are no significant spatial variations in erosion rates along a given bank but contrasts in the magnitude of erosion between the north and the south banks can be related to the relative exposure of a bank to average wind velocities, total duration of winds and the effective wind-wave fetches.
Databáze: OpenAIRE
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