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Title: Assessment of flows in meandering compound channels (252/2/T)
Author: C.S. James
Author: J.B. Wark
Document Type: Monograph
In October 1991 the National Rivers Authority (NRA) commissioned HR Wallingford to produce a hydraulic manual, giving NRA engineers a more accurate method of estimating stage discharge relationships in meandering compound channels. The development of the assessment procedure was to be based on the SERC Flood Channel Facility (FCF) Phase B tests and other suitable data sources, from both experimental and field information. This report summarizes the development of the procedure, gives a worked example and discusses further work. The analysis considered both inbank and overbank flows. For inbank conditions, there are a number of existing methods and these were reviewed in the light of the Phase B data. Modification of an existing method (SCS, 1963) was found to give satisfactory results over a wide range of test conditions and this has been recommended for use with inbank conditions. For the overbank case, a new approach was adopted which quantified the loss mechanisms which occur in meandering compound channels. The main loss mechanisms are friction losses, losses due to secondary circulations driven by shear imposed by the flood plain flow, and expansion and contraction of the flow as it passes from main channel into flood plain and vice versa. The new procedure splits the flow into four flow zones: the main channel below bankfull level, the flood plain within the meander belt and the flood plains either side of the main channel beyond the meander belt. For a given stage, the discharge is calculated as the sum of the zonal discharges. The new procedure was found to give substantially better results than existing methods.
Publisher: National Rivers Authority
Publication Date: 1993
Publication Place: Bristol
Subject Keywords: Flow rateChannels (geography)FloodplainsDischarge (hydrology)
Extent: 83
Total file downloads: 312

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