Dealing with stormwater

Stormwater is an asset often regarded as a nuisance. As recent events around the country point out, stormwater in sudden large amounts is a considerable problem in some localities.

Stormwater is defined as rain water that falls to the ground. When rain hits our impervious rooftops, footpaths, road surfaces, car parks, etc. it is normally channeled away through a drainage system that often ends up in our natural waterways.  Any sediments and pollutants picked up on the way will end up in our creeks, streams and wetlands.

By passing directly through drains, the stormwater hasn’t soaked into the soil where it would recharge local groundwater sources and contribute to maintaining a healthy soil biota; the micro-organisms, animals and plants that exist in the soil.

Lost down the drain

Retarding basins are often constructed to help minimize the risk of flooding during heavy rain periods. A retarding basin may simply be a low area of land that for most of the time is just covered in grass or it may be a properly constructed wetland that contains some water 100% of the time and is a biodiversity hotspot.

Froggy Hollow retarding basin Civic Park Drouin

Individually, we can help mitigate the effects of large stormwater run-off events by ensuring our own properties are as permeable as we can make them: plant more plants to soak up the water, replace concrete patios and footpaths with flagstones or a more permeable material (gravel, mulch, permeable concrete or asphalt, etc.), swap lawn for native plants, incorporate trenches into a sloping garden design, construct a ‘rain’ garden, etc.

A few enlightened local governments are exploring various engineering strategies to better deal with stormwater runoff. Street trees in high pedestrian areas are planted with a surround of permeable material that allows stormwater to soak into the root zone but is safe for pedestrians to negotiate. Roadside gutters are constructed with ‘breaks’ to allow the water to soak into the root zones of the trees on the roadside. Rain gardens are built between the footpath and the road – much more efficient at absorbing water than grass ‘nature strips’.

Permeable street tree treatment Moe

Roof gardens, ‘green’ parking lots, increased tree canopy are further examples of green infrastructure that are practical ways of efficiently dealing with increased stormwater run-off that will come with predicted heavier and more frequent rain events. By relying on plants, soil, and natural systems to manage rainfall runoff, green infrastructure tackles urban stormwater issues and boosts climate resilience.