Help prevent local flooding, improve the local environment and increase the value of your house

Help prevent local flooding, improve the local environment and increase the value of your house: that cant be a bad deal can it!

With the recent flash floods in London and the warnings from continental Europe of more to come, I thought now was a good time to return to my theme about the damage done by concreted gardens.

In a recent report, the Royal Horticultural Society warned that paving over our front gardens has a surprising impact on the wider environment. Hard-surfacing gardens can also cause flooding and increase local temperatures?

Gardens can soak up rain, while paving, tarmac and concrete are less porous and increase the amount of rainwater that runs off by as much as 50 per cent.

This additional water usually flows into street drains, which can’t always cope with the thousands of extra litres in a storm.  

RHS Principal Environmental Advisor, Rebecca Matthews Joyce, explains, “The water has to go somewhere and, even if you are not flooded, it might be affecting your neighbours downhill.”

The report continues with further warnings:

The other main environmental impacts are at local level. “If vegetation is lost from our streets there is less to regulate urban temperatures,” explains Rebecca. “Hard surfaces absorb heat in the day and release it at night, making it hot and difficult to sleep.” This is part of the ‘heat island effect’, which can also be responsible for poorer air quality and localised weather conditions, such as thunderstorms. Plus, higher temperatures mean that air conditioning units are more likely to be installed, which use extra energy and fossil fuels.

Attractive front gardens have benefits for people too. They provide screening and privacy, creating a green oasis for enjoyment. Tending your garden at the front of the house gives neighbours the opportunity to meet and can help to build community spirit. 

There are also financial incentives for keeping front gardens. London Assembly's Darren Johnson explains, “If lots of homeowners along a single street pave over their gardens, then the average house price can drop.” Leafy streets attract buyers and make the area more desirable. However, in contradiction, estate agents point out that in areas with controlled parking zones, off-street parking can actually add thousands to the asking price.

The other costly issue is subsidence. According to Neil Curling, Senior Subsidence Manager at Halifax Home Insurance, “Hard paving can cause severe subsidence as it reduces or stops rainfall getting into the ground.” This can cause the soil to shrink, especially if it is predominantly clay, which has consequences for structures built on it. Garden walls, paths and houses may develop severe cracks.

The Environment Agency is also worried about this issue, in their, Guidance on the permeable surfacing of front gardens, they say: 

Replacing grass and plant beds with concrete and asphalt surfaces means that water does not soak into the ground. This reduces the amount that reaches our natural underground aquifers. Some water that soaks into the ground will evaporate back into the air, causing a cooling effect around the house. This is lost if the garden is covered with hard impermeable surfaces and can cause local temperatures to rise (often referred to as the urban heat island effect).

While paving over one front garden might seem of little consequence, the effect is cumulative.

The worst culprit for paving over front gardens is London, with half of all front gardens paved over and a 36% increase over the last ten years. London also had the biggest decrease of plant cover in front gardens in the UK, with five times as many front gardens with no plants compared to ten years ago.

When the London Assembly examined aerial photographs of the capital, it found that 12 square miles of front gardens are now under paving. This is the equivalent of 22 Hyde Parks. “If this was a real park that had been lost, there would be a huge public outcry,” says Darren Johnson, chairman of the London Assembly’s environment committee.

Translated to the local level, the figures are still astounding. A typical Ladder garden is 70 square feet. In my road there are 130 houses: that means the total front garden area is 9,100 square feet. I think I'm right in saying that in my road, most of the gardens are concreted. But, let's be generous and say only 75% are. That means that the total area of concreted gardens is 6, 825 sq ft.  That's an area bigger that Fairlands Park. 

Translating that to the whole Ladder, would give a concreted area of about one-fifth of a square mile. For the whole of Harringay (neighbourhood), it's between a third and a half of a square mile.

Thinking of only environmental issues, what impact must that have?

Some people worry about what to replace the concrete with. Small stones or gravel provide a perfectly good surface for your bins to wheel alomg and stop the surface getting muddy in the winter. If you must have hard-standing, there plenty of man-made permeable surfaces.

Check-a-trade suggest the cost can be as low as £250:

A tradesperson will normally charge around £150 per day to remove a concrete patio, but they rarely work alone so you should allow another £100 per day for a labourer as well.

It should usually take no more than a day for two people to remove your concrete patio.

So, if you've been thinking about de-concreting your garden, now's a good time to crack on and get it done!

Sources:

RHS, Are we parking on our gardens? Do driveways cause flooding?
RHS, Greening Grey Britain
Environment Agency - Guidance on the permeable surfacing of front gardens