Your Dam Your Responsibility (PDF~1.2MB)

4 Planning to Build a Dam
becomes apparent as surface leakage only when the internal erosion has already well
progressed.
The storage basin must also be impermeable to hold water and where this is not so,
expensive clay lining may be required. It is not unknown that excavation to obtain
suitable materials for the embankment has stripped away all protective impermeable
material in the storage basin, leaving a clear path for leakage under or around the
embankment, or in some other direction.
Note: If the soil type is suspect, get professional advice on soil treatment as the
construction procedures on their own cannot perform the impossible on poor soil types.
4.5 Considerations at Investigation Stage
4.5.1 Environmental
When a Licensing Authority receives an Application for any licence under the Water Act
(in respect of a new dam), whether or not on a waterway, they will refer a copy of the
Application to the:
(a) Department of Sustainability and Environment, for farm planning and environmental
reasons including:
• aboriginal cultural values;
• matters of national significance;
• native vegetation (outside the riverine and riparian zone); and
• flora, fauna and river ecology within the affected area.
(b) Catchment Management Authority, whose region includes the site of the proposed
dam, for waterway management reasons.
(c) Local government, whose municipality includes the site of the proposed dam, for
planning requirement and potential impacts on:
• adjoining properties;
• visual amenity/impacts;
• native vegetation (outside the riverine and riparian zone); and
• roads and other infrastructure.
4.5.2 Compensation Flow Requirements
As a condition of the Licence to Construct and
Operate Works on a waterway, there will be
a requirement for the storage dam to make
provision for a by-pass channel around the dam
or an outlet by means of a pipe through the structure.
This will allow predetermined water flows to be passed down the waterway. Your dam
will only be permitted to harvest a certain amount of water depending on the flow
patterns of the waterway.
The by-pass channel or outlet pipe and valve comprising the outlet works will need to be
sized to suit the compensation flow requirements. This outlet pipe has additional benefits
in that it is a means for releasing water from the storage in the event of a problem with
the dam wall.
When the dam is full, a spillway is used to pass excess flows.
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