Flow Resistance in Ice-Covered Alluvial Channels

Abstract

This paper describes the influences of floating level ice covers on flow and bed-load transport in alluvial channels and proposes a semi-empirical procedure for calculating flow resistance in such channels. The procedure can be applied in conjunction with several existing methods for estimating flow resistance in alluvial channels under open-water conditions. Previously, cover influence was poorly understood, with the consequence that flow-resistance calculations for ice-covered alluvial channels entailed an inordinate amount of guesswork. The cover influences described herein were determined from the results of experiments conducted with a laboratory flume. The main findings of the flume experiments are that ice covers increase flow depth, decrease bulk flow velocity, increase dune length, and significantly decrease bed-load transport rate. Additionally, it was found that sediment transport relationships developed for open-water flow are applicable to ice-covered flow provided they are used in conjunction with estimates of actual bed shear stress. The proposed flow-resistance procedure enables such estimates to be made.