A PRACTICAL GUIDE TO EFFECTIVE DISCHARGE CALCULATION
David S. Biedenharn1, Colin R. Thorne2, Philip J. Soar3,
Richard D. Hey4, Chester C. Watson5
ABSTRACT: This paper presents a procedure for calculating the effective discharge for rivers with
alluvial channels. An alluvial river adjusts the bankfull shape and dimensions of its channel to the wide range
of flows that mobilize the boundary sediments. It has been shown that time-averaged river morphology is
adjusted to the flow that, over a prolonged period, transports most sediment. This is termed the effective
discharge. While it may, under some circumstances, be possible to estimate the dominant discharge from
the bankfull discharge, in practice, identification of bankfull stage in the field is often problematic. The
dominant or channel-forming discharge may more reliably be found by calculating the effective discharge
provided that the necessary data are available, or can be synthesized, and the calculations are properly
performed. The procedure for effective discharge calculation presented here is designed to have general
applicability, have the capability to be applied consistently, and to integrate the effects of physical processes
responsible for determining the channel dimensions. An example of the calculations necessary and
applications of the effective discharge concept are presented.
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