Appendix G - Slope Stability Certification Report · MCU25/0022

      •    Control the flow volume
      •    Control the flow path
      •    Reduce run off velocity
  Many techniques are available to achieve these objectives. The following list provides some
  common methods for Stormwater Management.
      •    Vegetation Retention / Re‐Establishment: Plants provide a means of retarding
           surface flow as well as acting as a natural filter. Where possible, natural vegetation
           should be left undisturbed. Establishing vegetation cover in potential problem areas
           (steep slopes, gullies etc.) will also assist in reducing erosion.
      •    Surface Drains / Grassed Swales: Well grassed diversion drains provided above
           exposed surfaces redirect water around erosion prone areas. These should be used in
           conjunction with level spreading devices to disperse fast moving, concentrated surface
           flows.
      •    Level Spreaders: A level spreader typically consists of a coarse gravel filled trench
           running parallel to the natural surface contours. This redistributes surface water and
           allows concentrated flows to spread over a large area and decreasing the velocity.
  Surface Erosion
  Soils lost from land surfaces as a result of surface water run off not only removes valuable
  topsoil from the area, but also result in siltation of downstream waterways when the sediments
  settle. Loss of soil is usually the result of leaving bare surfaces exposed to the elements, or
  from concentrated surface flows scouring the natural surface. Temporary measures can be
  taken to control and contain sediment removal during construction such as:
      •    Covering Stockpiles: Stockpiles of soil can be covered with plastic sheeting and re‐
           spread when construction is completed.
      •    Sediment Control Fencing: Hay bales or Hessian sacks supported between pickets
           and placed across the paths of surface water can catch sediments for future re‐
           spreading. Specialised sediment fencing is available for broad scale hillside scouring
           protection.
      •    Sediment Basin: A suitably sized earth basin may be constructed during the
           development to capture turbid stormwater runoff, where the sediment is allowed to
           settle before the cleaner water is pumped to a legal point of discharge. The sediment
           should be regularly emptied during drier periods.
  In general, it is recommended that all development on hillside areas should follow Good
  Hillside Construction Practice recommended in the information sheets presented in Australian
  Geomechanics Society “Practice Note Guidelines for Landslide Risk Management”,
  Australian Geomechanics Vol 42 No. 1 March 2007. An extract is attached as Appendix E.




193 Sankeys Rd Slope Stability Certification
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