Building sites are one region where erosion occurs in urban areas. This is because the vegetation is removed. As a result many building sites have to control the movement of sediments when rain washes the top layer of soil off.
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| note the sediment fences to stop soil entering the storm water system and keep water quality high in nearby creeks/rivers |
Developed areas
In urban areas which are largely developed, the impermeable surfaces of roofs, paths and roads cause stormwater to be concentrated and fed into creeks and rivers. This causes a pulses of high and then low water flows between rain. During and immediately after rain when the water flows are high, they erode the sides of the creeks and rivers. This in turn means that sediment is picked up and deposited elsewhere.
With this in mind, we began looking at the Lake Macquarie area as a place where erosion and sedimentation was taking place. Not only is there erosion taking place in the creeks due to development, but the sediments were filling the main lake area. The council has been working with community groups to revegetate affected areas and constructing artificial wetlands. As schematic diagram is below:
Apart from acting as a sediment trap and removing nutrients from the water, artificial wetlands slow the flow rate of water and in doing so, they reduce the amount of erosion from the path that they travel. Various features of artificial wetlands are discussed in your handouts.
Apart from these wetlands, community groups have been heavily involved in revegetating areas around creeks etc that have been eroded to try and stabilise the situation. Once again the roots of the plants will hold the soil together and it should no longer wash away.
Finally, the council has adopted codes of practice that must be adhered to by building site managers. These include trapping sediment on site so that it is not washed away.
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