Wednesday, July 6, 2011

Water Sensitive Urban Design

This is a concept that arose during Lagoon Day which is about designing urban environments so that they are more closely matched to the original water cycle that existed prior to settlement. The concept is being promoted in the city of Brisbane, Australia. It should be much easier to adopt this concept in Rarotonga where the population is much smaller and development is less advanced. The concept is based on the principle that the construction of roads and buildings causes rain water to accumulate in one area causing floods. This rain water would normally be taken up by plants/trees and transpired into the atmosphere or it would sink into the ground to become groundwater which eventually moves to streams and (in our case) the coral lagoon.

The concrete and asphalt on footpaths and roads prevents this water from filtering through the ground and creates storm water drainage problems as well as flooding.

While the natural reaction might be to build larger storm water drains, this only creates a new problem – the drainage of polluted and unfiltered storm water directly to our sensitive coastal coral reef environment. In Brisbane, the concept of Water Sensitive Urban Design has been promoted because of concerns about the deterioration of Brisbane’s coastal marine environment. Ways to protect the coastal marine environment and mimic as closely as possible the original water cycle include maximizing water efficiency (recycling water, saving wetlands), installing rain water tanks (which also reduces demand on the reticulated water supply), restoring streamside vegetation, installing rain-gardens (to receive excess storm water from roof tops and roads) and building car parks, driveways and footpaths from porous materials.

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