Stormwater problems arise from urbanisation and predominately occur in cities. The two key issues associated with stormwater is dealing with the amount of stormwater (quantity) and dealing with the cleanliness of the stormwater (quality) entering our streams and beaches. Each issue poses different threats to homes, properties and the environment.
Stormwater quantity
Increased hard (impervious) surfaces such as roads and roofs stop the stormwater from seeping naturally into the ground, which leads to greater volumes and higher peak flows flowing over the land.
Increased stormwater runoff can cause flooding of houses and land slips and can accelerate erosion of the land.
Stormwater quality
North Shore city contains the longest urban coastline in New Zealand and as all stormwater leads eventually to the beaches it is paramount that the amount of contaminants in our stormwater are reduced. Stormwater washes clean the surfaces it flows over. This means anything spilled or left lying on the ground will be washed downstream.
Things like litter, concrete dust, cigarette butts, grass clippings, detergent from car washes, roof particulates like zinc and copper, paint, oil and petrol, and bits of tyres from the roads all get transported via stormwater runoff to the sea and can kill the ecology along the way.
