Why don’t our cities cope with heavy rain?

By Amy Edwards

1 December 2017

people crossing the road as it rains

As heavy rain hits, how do our cities deal with it?

It’s officially the first day of summer but you wouldn’t know it in Victoria as the state braces itself for a deluge of rain.  Although this opening of the heavens might be giving your plants a good water, extreme rainfall events can actually cause major flooding, car accidents, property damage and even loss of life. And we know that as our climate changes we’ll see more severe storms and rain events and lengthier droughts.

While our research can’t prevent extreme events from happening, it can help protect people from their effects.

“Planning cities to cope with extreme rainfall events is critically important to minimise property loss, reduce danger to lives, and reduce any negative effects on the natural environment, especially waterways,” said Dr Simon Toze from our Adaptive Liveable Cities team.

Our research, based on water and future resilient cities, includes finding environmental-friendly solutions for long-term sustainability and water supply, preventing contaminants, as well as reducing discharge of water and wastewater while protecting human health.

Our cities are predominantly covered in artificial surfaces such as roofs, roads and pavements, which stops natural rainfall from penetrating into the soil and groundwater recharge. These impervious surfaces increase runoff, which can result in pollution of waterways with urban contaminants, and increased risk of flash flooding. Water Sensitive Urban Design approaches are designed to increase natural infiltration of rainfall, which can help in reducing runoff and pollution of waterways, particularly from regular rainfall events.

a paved surface with rain falling

Urban landscapes tend to have lots of impenetrable surfaces which can cause flooding

Using public open spaces and naturalising our water ways will be important in slowing water flows to reduce peak floods and help remove sediment and other contaminants out of the stormwater.

While our research is looking into how to significantly reduce disposal of our excess water and wastewater by looking at storage mechanism, improving sanitation and decreasing contamination of waterways, there are also things residents can do individually.

Rainwater tanks have the potential to reduce the impact of urban flooding, especially if tanks have available capacity to take on some of the rainfall. Therefore it can be helpful to ensure the tank is empty prior to a large rainfall event. Our previous research has shown that many people neglect regular maintenance of rainwater tanks systems, so make sure you keep it clean.

“An intense storm has the potential to fill a rainwater very quickly (e.g. 20 mm rainfall on 100 m2 roof can fill a 2,000 litre tank),” one of our senior research scientists Dr Magnus Moglia said.

“To ensure that rainwater tanks operate as designed it is important to check before the storm that gutters and downpipes are clear of leaf litter and other debris.”

Here are five things we can do to prepare for storms:

  1. Ensure that roads and parks as clean as possible to reduce contaminants being washed into our waterways.
  2. Encourage the growth of native grasses and bushes on the edges of our creeks and streams to slow down water flowing into the streams and help clean the water.
  3. Naturalise our creeks and streams, including creating floodable pond areas, to slow down water flows.
  4. Design more ways to capture and store water for later use, for example storing underground in aquifers.
  5. Understand that some areas in our cities will always flood and redesign them to deal with those floods.