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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  701P0904,  . (doi: 10.13031/2013.17362)
Authors:   Richard Hey and Dave Rosgen

Several design procedures are available for predicting the three dimensional morphology of natural stable rivers: analytical, empirical and analogue. First analytical, or rational procedures are the most theoretically sound as they are based on the simultaneous solution of a set of process equations which link the three dimensional morphology of the river (bankfull width, mean and maximum depths, slope, sinuosity, meander arc length and velocity) with the controlling boundary conditions (bankfull discharge and bed material load, bed material calibre, bank sediment and vegetation and valley slope). Second, empirical regime equations have been developed from field data using statistical methods. They simply link the variables defining channel form with one or more of the controlling variables. Third analogue, or geomorphological procedures enable designs to be scaled from the morphology of a natural stable reference reach of the required stream type.

The basis of these three distinctly different procedures are critically reviewed and compared. Field data are then used to evaluate their predictive capability. This indicates that significant errors can occur with both rational and regime equations even when used appropriately. Provided that reference reaches are correctly identified, the geomorphological procedure enables the three dimensional morphology to be specified within +/- 10% of the true value. Unlike the other procedures, which only predict reach average conditions, it also enables the morphology of riffles, runs, pools and glides to be prescribed. The rules for correctly identifying an appropriate reference reach are identified.

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