How you can protect your home against the growing threat of floods

Jane Knox is seen cleaning up her flood damaged property in the suburb of Auchenflower in Brisbane, Wednesday, March 2, 2022. (AAP)
Jane Knox is seen cleaning up her flood damaged property in the suburb of Auchenflower in Brisbane, Wednesday, March 2, 2022. (AAP)
Heavy rainfall is a problem everywhere. Given the nature of forecasts from climate change experts, homeowners around the world need to prepare for the risk of residential areas suddenly becoming flooded.

Storms are a danger all year round in many places, with even a summer thunderstorm capable of creating a deluge.

Homes that have never been flooded before, even those on a hill, can wind up with masses of water in their basement before homeowners have five minutes to prepare.

Rainfall can come so quickly that it isn’t possible for the ground to absorb it, and sometimes, it’s too much for the drainage systems too. That can leave floodwaters seeping into basements and tiny streams swelling into angry rivers.

Mostly, buildings located close to rivers or areas prone to flooding have some measure of protection – but even here, waters can far exceed what people imagined, meaning preparations never go amiss.

Luckily, some structural measures are very straightforward and relatively inexpensive.

Given the nature of forecasts from climate change experts, homeowners around the world need to prepare for the risk of residential areas suddenly becoming flooded.

Some solutions are “insanely simple” and can at least mitigate the damage caused by a wave of water, says Klaus-Jürgen Edelhäuser, from a German group of civil engineers.

It all starts in the basement. In a new building, you can have a white tank made of water-impermeable reinforced concrete or you can get a black tank sealed with plastic or bitumen sheeting. You can retrofit the latter in your basement although that can be very costly. Otherwise, you’ll need another concrete trough as an additional layer, according to a German disaster assistance unit.

The agency advises people to line their basement with tiles and other waterproof construction and insulation materials so if worst comes to the worst, it is easier to remove any mud that flows in.

Meanwhile, only use the cellar area as a workshop or storage area, not as a living area, say the civil engineers.

Also, ensure you don’t place any electricity sockets near the floor.

Overflowing drains

Drains are another area that can be a problem if you get a flood. You can install backflow valves in new buildings to prevent water from an overflowing sewer system from forcing its way through the sewage pipes into the house. You can also retrofit these into other residential buildings and these are mandatory in some places, according to Edelhäuser. “However, often they are not installed.”

These tend to be simple flap mechanisms. You’ll want an electronic model to deal with water containing faecal matter.

You can locate such backwater flaps at the point where the main wastewater pipe leaves the building – usually that is one point but there could be two.

Place the flap directly at a drain, for example at the washing machine or in the siphon of the sink. An additional point at the sink isn’t needed, however, says Edelhäuser. “It is definitely better to have the flap to cover the entire pipe.”

Clear as glass

Your windows are a further area of vulnerability and if floods hurl tree trunks or other large objects against a window pane and the water pressure is high, then the windows are not likely to hold up.

But your chances are better if there’s a moderate level of flooding. You can get “flood-resistant” windows which only let in a limited amount of water within a 24- hour period, a maximum of 240 litres, which is approximately the amount that a dustbin can hold, for example.

Windows that stay completely water-tight for 24 hours are also available. If you’re considering these products, then make sure you get a test certificate, as there’s no legal framework or regulated classification for them, says Frank Lange, from a German window and façade group.

Also, ask for an installation certificate after your windows are installed, or have them checked by an expert, he says. “The installation is the decisive factor,” says Lange. You don’t want there to be any gaps.

Small streams can turning into raging rapids after heavy rainfall.

Meanwhile cellar windows are usually installed with the opening facing inwards but if you’re preparing for floods, it’s better if the opening faces outwards, as that can better distribute the water pressure, says Lange. He points out that it is not just a question of getting a window from the DIY shop and installing it the other way round, however. “The window has to be able to withstand the flood pressure.”

He says that also applies to modern windows that are watertight or water-resistant if they can be opened inwards.

Build for the future

Meanwhile, walls located in front of light wells can at least protect against a certain height of water, according to the BBK.

Make sure when you’re building a property that the water is always diverted away from the house. “That is an absolute must,” says Edelhäuser.

You want a slope that leads away from the building so no water collects or seeps directly into your home.

Check that there are areas where water can be absorbed into the ground and lay grass rather than having a paved area. You can also create cisterns or consider a green roof.

There are many easy solutions that will better protect your home from minor flooding. If a small stream flows nearby and occasionally rises, then build a small plinth wall around your property’s boundary to mitigate any flood damage.

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