FLASH FLOODING affects cities across the world and has become more common because of climate change. This is expected in Metro Manila every time it rains but what is surprising is that other cities in the Philippines also experience flooding now.

Flash floods usually happen during heavy rainfall when the amount of water is too much for drains and sewers to deal with. It can occur very quickly and without much warning. Roads can become unpassable (with vehicles abandoned) and homes and stores damaged by floodwater.

Floods can affect also key public infrastructure including transport networks and hospitals. Why does it happen in cities and towns?

Urban areas are more likely to experience this type of “surface water” flooding because they have a lot of hard surfaces – everything from paved front gardens to roads, car parks and high streets. When rain hits them it can’t soak into the ground as it would do in the countryside.

Many factors contribute to flooding but climate change makes extreme rainfall more likely. A warmer atmosphere can hold more moisture and so these storms become more intense.

In many countries, flash flooding used to be relatively unusual. But these heavy short-duration bursts from thunderstorms, which cause flash flooding are becoming more common.

Research suggests flash floods – measured as 30mm of rain per hour – will increase five fold by the 2080s, if climate change continues on its current track. What can we do?

Changes could be made in towns and cities to protect against the worst effects of flash floods. Flood experts say urban areas could benefit from changes like permeable pavements and green roofs that can help rain water to soak away rather than causing floods. Lush vegetation could also help soak up a lot of water.

Knowing that heavy rainfall is on its way can make it easier to mitigate against the risks of flash flooding. Weather and flood forecasting science has improved rapidly and it is now often possible to forecast surface water flooding events in advance.

To protect your home, you can check if your area is at risk of flooding. Living away from a river does not necessarily mean you are safe from flooding. But it is also possible to take preventative measures. Because our house is in a low-lying area, we constructed covered canals around our property for drainage into a nearby river.

If you are making changes to your home, choose tiled flooring (ceramic tiles instead of linoleum) and move plug sockets further up the wall. And Plant Plant Plant –  plantitos and plantitas – in your yard and vacant lot!

Drivers also need to be careful to avoid rising waters, as many flood-related deaths are in vehicles. According to experts, just 30cm of water is enough to move a car. By Manny Palomar, PhD (EV Mail November 28-December 4, 2022 issue)