MORE INFORMATION- Water

Stormwater

Stormwater is all the water that runs off hard surfaces in our catchments.  This water is caught in urban areas by our stormwater system.  The Stormwater System is the network of drains and pipes that collects rainwater runoff from all the towns, suburbs and industrial areas of Wyong Shire and transports it to wetlands, streams, lakes and the ocean.  The Stormwater System reduces flooding in our towns and suburbs and helps them dry out more quickly after rain.  Stormwater can carry many pollutants and litter items into our waterways and wetlands.  For this reason we need to mange our stormwater and the potential impacts.



Figure 1:  Stormwater Drains (Source: Wyong Shire Council)

The Stormwater System has three main kinds of environmental impact;

  1. It reduces the amount of rain that soaks into the ground throughout the Shire. It does this by collecting rain that falls on roofs, paths, roads and carparks. This means that less rain soaks into the ground to feed the water table and be used by plants.
  2. It increases the amount of rain that is flushed into natural streams and wetlands. This changes the environments of those places and can cause some plants and animals to die because of erosion, sedimentation and too much wetting.
  3. It increases the amount of pollution that is flushed into natural waterways. As stormwater flows off buildings, carparks, roads and factory yards, it collects many types of pollution (see pollution list on next page). Since the Stormwater System is designed to move water quickly, it also works like a pollution expressway. Even harmless things such as leaves from trees, can become pollution when large amounts of them are dumped at the end of a drain (see “Using up the oxygen” experiment).

Although some drains have gross pollution traps or other ways of filtering stormwater, very little of Wyong Shire’s stormwater is treated before it flows into our wetlands, streams and lakes.  Wyong Shire Council is working towards improving the stormwater system by improving stormwater treatment in our major drainage areas and by introducing Water Sensitive Urban Design.  Water Sensitive Urban Design (WSUD) is not a new concept it uses engineering and environmental management tools to better manage water in urban areas to suit its ecological needs.  WSUD encompasses all aspects of integrated urban water cycle management including; water supply, sewerage and stormwater management. It represents a significant shift in the way urban areas are planned and designed. These processes then adequately address the sustainable use of water environments in urban catchments.  The photo below shows a WSUD drainage channel that has been created in a new estate in Hamlyn Terrace.  This channel will filter the stormwater through the rock and aquatic plants and remove heavy impurities such as sand and grit before the water reaches the stormwater drainage system.



Figure 2:  Water Sensitive Urban Design – Hamlyn Terrace Estate (Source: Wyong Shire Council)

 

Table 1: Stormwater Pollutants

Pollutant

Urban Source

 

 

 

Sediment

Pavement wear
Spillage/illegal discharge

Fallout from atmosphere
Car washing

Weathering of buildings/structures
Organic matter (leaf litter, grass…)

Vehicle wear
Land surface erosion

Nutrients

Animal/bird faeces
Fallout from atmosphere

Fertiliser
Organic matter

Sewer overflows/septic tank leaks
Spillage/illegal discharges

Detergents (car washing)

Oxygen demanding substances

Animal/bird faeces
Fallout from atmosphere

Organic matter decay
Sewer overflows/septic tank leaks

Spillage/illegal discharges

 

pH (acidity)

Fallout from atmosphere
Spillage/illegal discharge

Organic matter decay
Erosion of roofing material

 

 

Micro-organisms

Animal/bird faeces
Organic matter decay

Sewer overflows/septic tank leaks
Herbicides

 

 

Toxic substances

Pesticides
Spillage/illegal discharge

Herbicides

 

 

Sewer overflows/septic tank leaks

Heavy metals
Fallout from atmosphere

Spillage/illegal discharges
Vehicle wear

Sewer overflows/septic tank leaks
Weathering of buildings/structures

 

Gross pollutants (e.g. litter)

Pedestrians and vehicles
Waste collection systems

Spills and accidents
Leaf-fall from trees

Lawn clippings

 

Oils and surfactants

Asphalt pavements
Spillage/illegal discharges

Leaks from vehicles
Car washing

Organic matter

 

Increased water temp

Run-off from impervious surfaces
Removal of riparian vegetation (shade)