CGRG Bibliography of Canadian Geomorphology
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Author : Gomi, T.; and Moore, R.D.
Date : 2003.
Title : Interactions of stream, hyporheic, and hillslope flows along a headwater channel.
Publication : Canadian Geophysical Union. Annual Meeting, May 10 -14, 2003. Banff Centre, Banff, Alberta.
Issue :
Page(s) :
Abstract
Hyporheic exchange is an important control on solute transport and transformations in riparian-stream corridors. Dynamics of hyporheic flow vary with stream discharge, substrate type, channel morphology, and the hydrogeomorphology of the hillslope-riparian-stream continuum. Because of the tight linkages between the hillslope and channel, and the presence of geomorphic features that promote hyporheic exchange (e.g., channel steps), interactions between stream, hyporheic, and lateral hillslope flows in a forested headwater channel may be unique compared to its downstream counterpart. We examined interactions between stream water, hyporheic exchange, and lateral inflow using constant rate injection of a conservative solute during low and high base flow periods in three reaches along a headwater channel in coastal British Columbia. Transient storage and lateral inflow were estimated using the OTIS-P computer code. Piezometers installed in the streambed and riparian zone were used to measure hydraulic gradients and sample tracer concentrations in the subsurface. In the upper reach (mean channel gradient (S): 17 %, bankfull width (W): 1.0m), although the channel was confined by the hillslope, very little hillslope contribution for base flow generation was observed. Significant lateral inflow from the hillslope was found within the transitional reach (S: 11%, W: 1.5m). In the lower reach (S: 5 %, W: 1.3m), hillslope contribution was smaller because of less confined hillslope and gentler channel and hillslope gradient. In sections dominated by wood steps, we observed strong downward hydraulic gradients upstream of the steps, and weak upward gradients in the downstream pools. Hyporheic flow and subsurface mixing were subdued in the vicinity of concentrated lateral discharge points of hillslope flows. Therefore, the interactions among stream, hyporheic and hillslope flows appear to be controlled dominantly by the channel steps, which produce vertical exchange across the bed, as well as by the gradients of adjacent hillslopes and the width and gradient of the riparian zone, which influence both the lateral inflow of hillslope flow and possibly the opportunity for lateral hyporheic flows.
Bibliography of Canadian Geomorphology