Activity Group: Stormwater Drainage Activity: Stormwater Drainage Council’s Rivers and Land Drainage Department provides flood protection from the main rivers for some rural buildings and land. Where the main rivers and How this Activity Contributes to the Vision and Related drains pass close to the urban settlements, close liaison is required to ensure Community Outcomes stormwater and river management practices are well coordinated. Rural locations frequently rely on natural channels and local experience to avoid This Activity helps to achieve the Vision by enhancing quality of life in urban flooding of dwellings and outbuildings. locations and avoiding contamination of natural freshwater environments. It also contributes to the Community Outcomes of Environment, People and Economy The urban stormwater systems consist of natural components such as swales, as outlined below. channels and ponding areas as well as constructed assets — including inlet sumps, stormwater mains, manholes, pump stations, retention areas, secondary Outcome Actions flow paths and soak holes. Over 90% of the stormwater assets in the Environment Controlling stormwater and managing drainage provides major Marlborough region are located in Picton and Blenheim (see the Asset environmental, economic and social benefits. Description table on the following page). Managing the quality of urban stormwater run-off prevents The local terrain can also determine the role of assets in the system. In damage to the natural receiving environment. Blenheim it is important to drain the flat valley bottom as quickly as possible, People Safeguarding residents and their property from the risks of while the stormwater assets at the base of the Wither Hills have a role in stormwater flooding. detaining the water run-off to delay its concentration downstream and avoid flood accumulation on the valley floor. In some areas a degree of surface ponding can be tolerated and is even a desirable design feature. In other areas Economy Enabling commercial and industrial activities to be carried out it is a sign the system is overloaded. without disruption from flooding. The settlements at Picton/Waikawa lie at the base of a number of steep natural What is this Activity About? catchments that quickly accumulate and concentrate stormwater into managed watercourses that run through the urban area. This topography poses a different Council provides a stormwater drainage system to manage stormwater run-off set of challenges for land drainage. from urban catchments. Collection and disposal of stormwater contributes to: minimising the incidence of flooding to protect the community from harm Why We Provide these Services • Environmental Risks — Council owned stormwater systems must take • minimising damage to properties from flooding reasonable care to prevent the conveyance of pollutants into the natural facilitating commercial and residential development environment. Rainwater falling on urban areas picks up and conveys all sorts of • waste materials to watercourses, and can also dissolve harmful substances. • protecting the aquatic environment through the management of water Pollution can occur through careless or accidental spillage of harmful materials quality from urban stormwater run-off or by reckless tipping of contaminants into the stormwater system. Council aims to control these risks through education, regulation and the installation of • reducing erosion. drainage infrastructure which provides a level of environmental protection. What We Do and Where We Do It Businesses which are considered to be carrying out high risk activities are Stormwater infrastructure is installed in areas where urban development has required to install interceptors in their drains and to cover impermeable areas encroached onto natural drainage pathways. In areas where hard surfaces such from rain. If a pollution event occurs Council will immediately respond to mitigate as roads and buildings have covered land there is less soakage of rainfall into the effects and investigate the cause. the ground, and properties need to be protected from stormwater run-off. 2018-2028 Long Term Plan Page 86