The Problem and Its Solutions
The Dawesville region faced a persistent issue of blue-green algal blooms, primarily caused by the phosphorus load in the water from agricultural run-off and industrial practices. The situation worsened as stakeholders disagreed on the approach to remediation, and politics muddied the waters. However, several attempts were made to address the problem.
Among these efforts were the development of a long-lasting “sandplain” superphosphate by the fertilizer manufacturer CSBP, top-dressing of farmlands with bauxite tailings from Alcoa’s mines, reforestation, revamping of aquatic fauna habitats, and the removal of large-scale industries like piggeries. There was also an emphasis on educating farmers about better farming practices and imposing restrictions on phosphate-rich fertilizers.
The Ultimate Solution
After extensive research, environmental scientists, Professor Arthur McComb and Ernest Hodgkin, pinpointed the root of the problem – the agricultural and industrial practices in the catchment area that led to a high phosphorus load in the water. Their solution proposed a new channel to the ocean, which would increase water exchange between the estuary and the ocean, flushing out nutrients and increasing the estuarine system’s salinity to levels that would inhibit the growth of blue-green algae.
The Dawesville Channel
The solution led to the construction of the Dawesville Channel, after several years of deliberations. The project, completed in April 1994, cost $37 million and involved the excavation of about 4.5 million cubic meters of material. In addition to the excavation, the construction also involved breakwaters, training walls, a bridge, and a sand bypassing system.
The channel, 2.5 kilometers long, 200 meters wide, and between 6 and 6.5 meters deep, dramatically improved the area’s situation, resulting in no more blue-green algal blooms upon its opening. The channel is now spanned by the four-lane Port Bouvard Bridge and has seen the emergence of major residential canal developments, including the suburb of Wannanup and a golf course.
Sand Bypassing
An integral part of the construction was the incorporation of a sand trap to handle the natural south to north coastal movement caused by the prevailing south-westerly winds. This sand trap prevents the channel from silting up by mechanically moving approximately 85 thousand cubic meters of sand per year from the south to the northern side of the channel, maintaining the channel’s integrity and function.
In conclusion, the Dawesville Channel serves as a testament to innovative environmental solutions and the power of human ingenuity in confronting ecological challenges.
