Within our urban landscapes, creek lines are prone to degradation due to upstream flow modification and bank alterations. Channel erosion and deposition is a natural process for creeks of all sizes. However in many urban areas land use change and continued development have continued to impart extra pressure on local creeks. There are a number of general rules that you can follow to help maintain a natural balance of erosion and deposition.
Maintain riparian vegetation
The plants that grow on the banks and in the channel are very important for stability. It is best to ensure that ground covers, mid-storey and canopy species are present. At a minimum, any area not modified with hard engineering, must have a stable, established ground cover covering the banks to minimise erosion and deposition downstream.
Image source: Northrop
Maintain trailing plants and woody debris
Where fallen branches or growing plants accumulate in a creek, try to avoid removal. These features slow down water flow and decrease its erosion potential.
It should be acknowledged that in some circumstances, these features can become a flood hazards or cause localised scour, which may threaten infrastructure assets. In these cases, the debris may need to be removed. This should be discussed with a Council to assess the risk and best course of action.
Use "soft engineering" to stabilise channels
In certain circumstances it may be necessary to stabilise an eroding channel through re-grading the banks, adding vegetation and/or strategically placing natural features such as logs.
Works of this kind that require any re-engineering or contouring of the creek bank should be designed and constructed by appropriately qualified professionals and be carried out under a development application. Superficial works such as re-vegetation or other surface erosion controls may be carried out without a development application where otherwise legal in all other senses. Contact council if you are unsure if your planned works are suitable.
Use "hard engineering" to stabilise channels
"Hard engineering" includes works such as rock lining, channel re-alignment and/or other significant work which is sometimes required to stabilise a channel. These works should always be designed and constructed by appropriately qualified professionals and be carried out under a development application.
Any significant work within a channel must be in accordance with the Riparian and Water Management controls in Council’s relevant Development Control Plan.
Sound engineering design requires additional protection at all pipe and culvert inlets and outlets. This is due to the concentrated power of the flows exiting the internally smooth pipes. This increased power requires dissipating in order to protect the creek banks from turbulence and high velocities, which can otherwise cause scour erosion. To achieve this, a range of energy dissipaters can be utilised, including rough surfacing, basins, large protruding structures and graded spillways. Any of these structures should be designed by a qualified engineer using suitably sized natural materials and constructed in a manner that complements the receiving environment.
Further information can be found in the fact sheet guidelines for controlled activities - outlet structures from the Department of Water and Energy.