Water notes WN38 February 2009
Water notes for river management – Notes taken from a Department of Water document from 2009.
Advisory notes for land managers on river and wetland restoration
This Water note provides information on the problem of sedimentation of the deep pools of the Avon River system in the Wheatbelt region of Western Australia. It explains why deep pools are important to stream ecosystems, why the problem has occurred and the management practices that are used to reverse it and help prevent it from recurring.
Two case studies are described. These are the pool restoration projects for One Mile Pool and for Boyagarra Pool.
Sedimentation of the Avon River pools
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). The idea was to contain flood flows within the river channel and so avoid flood damage. However, the works resulted in extensive erosion and redistribution of sediment that was being held in place by fringing and channel vegetation and by natural bed controls such as logs, rock riffles and stable, vegetated sediment bars. As a result, many of the deep, permanent river pools of the Avon River are now either completely filled with sediment or are in the process of filling.
Read on by downloading the full article at The Department of Water.
