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Water, wastewater and stormwater

Stormwater

Rainwater in natural environments has a lot of soil to soak into, where it ends up either in underground aquifers, absorbed by plant roots, or running over saturated soils until it reaches streams, rivers, wetlands and lakes.

Stormwater catchment management plans Stormwater flooding hazard information

Urban areas have a lot less permeable soil available for rainwater to soak into, due to impervious surfaces such as concrete footpaths, roofs and bitumen roads. That results in more rainwater running overland (localised runoff), which is called stormwater.

New Plymouth District Council (NPDC) manages stormwater in the district’s urban areas, while Taranaki Regional Council manages other water hazards like the risk of flooding caused by big rivers overtopping their banks, or coastal flooding.

NPDC operates the urban stormwater drainage network, designed to manage stormwater runoff effectively.

The primary stormwater network operates during frequent, smaller storms and is formed by pipes, gutters and drains.

The secondary stormwater network comes into play during larger, less frequent storm events. These systems are designed to manage overflow from the primary network and include features like detention basins, swales, and overland flow paths. They help to prevent significant flooding and manage stormwater in a way that minimizes damage to property and the environment

How do we manage stormwater?

Management of stormwater is about mitigating its effects on people and the environment. Key stormwater issues for councils to manage are:

  • Localised ponding and flooding, especially during severe weather that has overcome the capacity of the stormwater network.
  • Water-borne pollution. As rainwater falls on urban areas, it ‘washes’ hard surfaces such as roads, carrying a load of pollutants, e.g. heavy metals, hydrocarbons and bacteria. These affect the ecological health of the receiving environment, such as a stream or the ocean.
  • Ecological health. As we pipe streams and drain wetlands, making land suitable for development, the effect on remaining freshwater bodies can see lower regular flow rates and extreme high flows during storms. The effects can include erosion, loss of habitats and biodiversity and poor water quality.

The Stormwater Vision and Roadmap is the guiding strategy for the management of stormwater in the district, and is comprised of two parts:

  • A strategic framework, in the form of a vision, aspirations and objectives, for delivering stormwater services, as well as a method to enable the current state to be measured, goals to be set and progress tracked. Vision Aspirations and Objectives
  •  A Stormwater Roadmap that outlines the actions required to achieve the three-year and 10-year goals. 

 

Page last updated: 09:44am Thu 27 March 2025

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