Rainwater tank trial helps stop flooding

North Shore City Council has just started an innovative rainwater tank pilot project in Glenfield that will provide a more environmentally-friendly way of reducing the risk of flooding to properties.

Properties in the Glencourt Pl, Seaview Ave and Stanley Rd experience flooding in heavy rain because existing stormwater pipes are too small to cope.

North Shore City stormwater programmes manager, Barry Carter, says the flooding problem provided an opportunity to trial the use of rain tanks in a well-established residential area.

"By collecting water from roofs rather than letting it run straight into the pipes, some rainwater can be used, and the rest released at a controlled rate.

"That reduces the peak load on the local stormwater system and the risk of flooding to downstream properties," he says.

Although rainwater tanks are used to lessen stormwater effects of new developments, this is the first time they have been used to help solve flooding problems in an existing development.

North Shore City Council is installing tanks including pumps and fittings at 20 properties where residents have agreed to have them.

The rainwater collected will be used to flush the toilet, do the laundry and outside the house, for example to water the garden or wash the car on the lawn. The existing public water supply will be retained for drinking water, kitchen and bathroom use.

"Owners will not only benefit from less flooding on their properties, but the average household could also save about $100 to $150 a year on their water bill," says Mr Carter.

Added flood protection in the form of swales - shallow, grassed drainage ditches that convey water and filter out contaminants - will also be constructed along the boundary of three properties to slow down run-off.

North Shore City Council will monitor each rainwater tank's performance and maintain it for two years after it has been installed, but then it becomes the owner's responsibility.

The pilot project could lead to further rain tank projects in other parts of the city as an alternative to providing more pipe capacity.

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