Sedimentation
Sediment entering waterways is a natural process, but human land use can result in excessive quantities which can cause problems. Sources of human derived sediment include:
- urban development
- agriculture
- forestry activities
- roads
- industrial and wastewater discharges
- housing developments.
The greatest impact of sediment entering waterways is on instream habitat. Sediment can fill pools, cover and fill in rocky bottoms and coat snags. This can reduce the available habitat and affect the breeding and feeding habits of native fish and aquatic invertebrates (for example, insects, snails, worms and shrimps).
Sediments suspended in the water column turn the water turbid (muddy). This reduces the amount of sunlight entering the water, which reduces plant growth and makes it difficult for predators such as fish and birds to hunt. Suspended sediments in the water column also interfere with the uptake of oxygen by fish and invertebrates.
Sediments also enter the marine environment through creeks, rivers and estuaries, again emphasising that what we do in our catchments affects our coast. Excessive sediments can kill marine plants and animals by smothering them or cutting off access to light.
Sedimentation is one of the factors causing the large decline in seagrass seen in recent years in Western Port. Although some areas of seagrass are recovering, others are still under threat and EPA is working in partnership to improve water quality.
Information on sediments is available on the Murray Darling Basin Commission's website.
Further information about sedimentation of rivers and streams is available from the Department of Sustainability and Environment's website.