Flow Distribution in Multiple Channels with Partial Ice Coverage

Ashton, George D.; ,

Flow Distribution in Multiple Channels with Partial Ice Coverage

by George D. Ashton, U.S. Army Cold Regions Research and, Engineering Lab, Hanover, United States,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract:

It is not uncommon for rivers to have multiple channels. The distribution of the total flow to the individual channels depends on their relative hydraulic characteristics of depth, width and surface roughness. The formation of ice covers on these channels may change the distribution of the total flow. Here I examine the extent of some of these ice effects on multiple-channel flow distribution for a two-channel situation. The effect of a thin skim of ice on one channel when the other channel is ice free is to shift flow from the ice-covered channel to the uncovered channel, but in a far greater proportion than the relative ratio of channel widths. The converse occurs also; that is, the increase in flow in a small ice-free channel is greatly increased by the addition of an ice cover on a parallel larger channel. The effects of relative ratios of the ice-associated roughness to the bed roughness are included in the results. I also examine the effect on stage for the case of partial ice coverage of a single channel, as occurs when ice grows out from the shore. It is essentially the same as published by Calkins et al. (1982) but does add an explicit result for the limiting case of a very thin ice cover. This allows the effects of roughness to be separated from the effects of simply adding a second boundary. Among the results is the finding that the stage rise associated with imposition of an ice cover does not abruptly change as final closure occurs, but rather increases steadily as coverage goes from 0 to 1.

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