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Councils improve stormwater management
In the winter of 2005, the Bay of Plenty was hit by an intense storm that caused flooding throughout the region. Tauranga and Matata were particularly hard hit and a state of emergency was declared. Climate change scientists predict more intense rainfall events like this and work is underway by many organisations to prepare for their impacts.
Tauranga has been particularly hard hit by storms and flooding.
The Council has responded by upgrading stormwater infrastructure
with new pipelines and culverts.
Heavy rains pour onto impervious surfaces like roads, roofs and driveways, collecting silt and other contaminants such as oil and chemicals before running into streams, estuaries and harbours. If it isn’t controlled, stormwater adds to erosion and flooding. This is what happened in Tauranga in 2005.
Tauranga City Council Stormwater Engineer John Palmer said, “Water flowed into private property and through buildings. It caused major slips where the water went down a driveway and came to the end and went over in a waterfall.”
Tauranga City Council’s response has been to upgrade stormwater infrastructure with new pipelines and culverts. It used the Ministry for the Environment’s climate change guidelines for local government to help identify risk factors and plan.
According to Palmer, a climate change factor for the next 50 years is now incorporated in the Council’s code of practice for development, and its stormwater system is designed for higher rain flow.
Changes in rainfall patterns in the Bay of Plenty also have implications for water quality in the Tauranga harbour. Industrial areas have been built on sites too flood-prone for residential development. When these areas flood, chemicals and materials are washed into the stormwater system and into the harbour.
“To improve the quality of the water we are trying to use source control. Companies are being asked to conduct activities, such as truck washing, in areas with concrete surfaces and bunding so material is trapped and only relatively clean water is allowed into the stormwater flow,” said Palmer.
Waitakare City Council is improving its stormwater management with a project called Twin Streams which it set up in 2003 to redress bank instability and degradation of local streams by litter and contaminants from overland flows. Sustainability Manager Lawrence Butcher said the project is resulting in behaviour change.
“People understand the problem, they understand it’s in their backyard. We’re doing a lot of work with the community and schools for long term sustainable outcomes so we don’t have to repeat the Project Twin Streams in another 10 or 15 years,” said Butcher.
Five local community groups are partners in the project and thousands of people have helped to weed, plant and maintain the stream banks.
With support from the Ministry’s Sustainable Management Fund, permeable paving has been used on sections of new walk- and cycle-ways to show how permeable paving, unlike concrete or bitumen, allows stormwater to drain through to the ground below.
For more information contact Katie Andrews-Cookson on (04) 439 7612 or katie.andrews-cookson@mfe.govt.nz
For more information about the Sustainable Management Fund contact Amanda Turner on (04) 439 7518 or email amanda.turner@mfe.govt.nz
