There are three main causes of the changes that have occurred in the biology and physical condition of the Avon River since the Avon River basin was settled. These are widespread catchment clearing, urban development and the River Training Scheme.
‘River training’ works were undertaken from 1956 to 1972 to reduce the risk of flooding. They involved the ripping and bulldozing of the riverbed and removing debris from the river channel. The form of the river channel was dramatically changed, from braided – where river flow passes through a network of small interlaced channels that reduce flow velocity and trap sediment – to a straightened single channel that increases flow velocity and erosive power (Harris 1996).
