Household Utilities: Potable Water: Storm Water.
For the city of Brisbane, the 1:20 year storm will deposit an average
of 251mm in an hour. February 2001 we had a 1:100 year storm with 300ml
of rain in less then
4 hours.
If stormwater management to be successful, it must be sensitive to
the site's existing natural processes, integrate with adjacent ecosystems,
be simple and logical in its execution, economical and require little
or no maintenance.
The
advantages of an above ground stormwater systems are:
1. Water conservation - above ground drainage should utilize
open channels (swales) and temporary
retention basins instead of storm pipes. This will permit infiltration
of surface water into the ground and help reduce the volume and rate
of run off.
2. Energy conservation - with planning, minimal volume and
extent of earthworks are required.
3. Ecologically sustainable - aboveground systems instead
of pipes will provide water for the native flora and fauna.
4. Aesthetically pleasing if well designed and constructed.
5. Economic savings - above ground systems have been shown
to save 20 - 50% of costs compared with traditional systems
6. Soil Conservation - is achieved by:
- Slowing the volume and rate of the surface run-off.
- Use of vegetation in reducing surface flow velocities and its
effect on surface erosion.
- Minimize earthworks to protect subsoil structure from the effects
of erosion.
- Rock energy dissipaters can be used where storm water pipes are
discharged and water is allowed to run into a swale. The rocks dissipate
the flow and prevent erosion.
- Roads should follow the contour of land where possible. Water
is encouraged to run to the verge of the road at low velocities
and be directed into gardens.
Observation of the Newton site indicates that the weathered rock, natural
gradient and existing vegetation are currently managing storm water
well. The addition of swales to slow the runoff of storm water will
permit the infiltration of surface water into the garden.
Links
http://www.bom.gov.au/climate/averages/
