Stormwater initiatives and solutions

Flood protection catchment management

To help us manage stormwater better and prevent flooding and pollution, we've prepared citywide catchment management plans (CMPs).

Our CMPs provide an overall strategy for management of stormwater and development of the stormwater network within a particular catchment. A catchment is an area where water, especially rainwater, collects when it follows its flow path downhill. Our CMPs form the basis of applications by North Shore City Council for comprehensive discharge consents from the Auckland Regional Council (ARC).

A typical CMP provides information for flood protection by identifying and recommending solutions to problems such as:

• Pipes or channels that are too small
• Areas where a stormwater system is needed
• Flooding
• Stream bank erosion
• Other issues which may have a potential impact on flood protection.
  

Flood hazard and plain maps

We've also developed city-wide flood hazard and flood plain maps, which include 100 year flood plains, flood sensitive areas adjacent to these plains and stormwater "hot spots" and are now updating these.100 year flood plains are the areas that are covered by flood water generated by a rainstorm that occurs on average once every hundred years. Flood hazard work involves:

• Identifying and improving critical assets, which cause major problems if they fail to function.
• Identifying and improving assets that are likely to fail because they can't hold enough stormwater. Examples are stormwater catchpits which are not well designed or installed, or are easily blocked by leaves and rubbish. We also locate and raise buried manholes and identify pipes that are partly blocked by tree roots and silt build-up.

Reducing erosion

Stormwater initiatives to address erosion problems include:

• Identifying streams, channels and outlets where erosion may become a problem
• Identifying, locating, registering and proactively maintaining retaining walls and stormwater dams
• Seeking new techniques to control erosion
• Establishing stormwater management areas so that development provides for the peak flows of stormwater discharged from the site to be no greater than that occurring prior to development.

Stormwater quality initiatives

Water quality and how it affects the environment is a major concern in North Shore City. Alongside Project CARE, our 20-year programme of works to improve beach water quality, we are also doing everything we can to improve stormwater quality.

Our stormwater quality initiatives include:

• Exploring new techniques for stormwater quality improvement that use the natural features of a site, such as streams, vegetation and wetlands
• Completing and reviewing catchment management plans for the city's 56 stormwater catchments
• Improving some of the existing water quality ponds to increase their treatment efficiency, such as Chelsea Estate and Link Drive stormwater ponds
• Installing 300 Enviropod stormwater filters in catchpits, to collect the litter and sediment before it reaches our beaches
• Changing our District Plan to make it more stormwater-friendly
• Implementing a new stormwater by-law to encourage people to consider stormwater as part of the resource consent process.

Stormwater projects

Stormwater Asset Management Plan

We developed a Stormwater Asset Management Plan to help us meet community expectations. This will provide:

• A complete and accurate asset register
• Better understanding of asset condition, including CCTV inspection of critical pipes
• A system to prioritise and update our long-term financial forecast.

The plan represents a significant step in the process of improving understanding and management of the public stormwater system and provides an overview of how to prevent erosion, minimise flooding and protect the environment in the most cost-effective way over the next 20 years.

What you can do

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