Restoration of the Hex river to equilibrium morphological conditions

摘要

The Hex river near the town of Worcester, South Africa, has a braided character iwth wide floodplains, a steep bed slope and high bed load. In June 1996, one of the highest floods on record caused severe head cutting, scouring the river bed by two metres which caused instability problems at two bridges. A comprehensive hydraulic study has been undertaken to identify the problem causes and impacts, and to establish a long-term solution for river equilibrium and bridge safety. Man's involvement in altering the river include: extensive mining of boulders from the main river channel with the aim of reducing flood levels which was foudn to be the main reason for head cutting, construction of bridges with fixed bed levels, river channel alteration, the construction of groynes on the floodplain, and closing of a major part of the braided system for agricultural development.