The key to protecting your home against flooding could be as simple as turning your gravel and tarmac patches into gardens, according to a leading expert.
A botanist has revealed planting ‘rain gardens’ of grass, shrubs and plants can help soak up excess water and combat flooding.
This past weekend, thousands of Britons were forced to evacuate their homes due to flooding from Storm Dennis.
According to the Royal Botanic Garden Edinburgh, a selection of both native plants and foreign foliage can help combat excess water.
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An example of urbanisation in Edinburgh between 1990 and 2015, showing the loss of valuable grassy areas that can soak up flood water
The flooded back garden in Exeter, where heavy rain has caused the River Clyst to burst its banks
Homeowners can often find the upkeep of a garden a hassle and difficult to find time to maintain as part of a busy lifestyle and opt for concrete or tarmac in their yards.
But according to the Royal Botanic Garden Edinburgh, maintaining a patch of earth has enormous environmental benefits.
‘We should not be fighting against nature, we should be living in harmony with it,’ said Kirsty Wilson, a garden designer at the Royal Botanic Garden Edinburgh, told The Times.
‘Don’t tarmac your garden. We can do so much more to mitigate the effects of climate change with native and non-native plants.’
RBGE has previously teamed up with flooding experts from Heriot-Watt University to create a rain garden to tackle flooding caused in part by climate change.
Rain gardens are shallow planted basins that allow rainwater to run off naturally into the ground using free-draining soil.
These ‘living laboratories’ use shrubs, wildflowers and grasses that can withstand occasional flooding.
Non-native plants including goatsbeard, giant rhubarb, leopard plants and granny’s bonnet have been found to be good at dealing with flooding.
These thirsty plants are able to capture plenty of water and can tolerate sodden conditions.
The RBGE’s rain garden, completed in spring 2019, which features a range of plants in a special mix of soil, compost, sand and gravel
WHICH PLANTS ARE RECOMMENDED FOR YOUR OWN ‘RAIN GARDEN’?
RBGE successfully used a range of native and non-native plants in their rain garden to mitigate floodwater.
The selected Scottish native plants include:
- Devil’s-Bit (succisa pratensis)
- Kidneyvetch (anthyllis vulneraria)
- Meadowsweet (filipendula ulmaria)
- Field Scabious (knautia arvensis)
- Alpine Sow-Thistle (cicerbita alpina)
- Wood Fescue (festuca altissima)
The selected non-native plants include:
- Hand Mazz (aruncus gombalanus, China)
- Giant Rhubarb (gunnera manicata, Brazil)
- Fischers Ragwort (ligularia fischeri, East Asia)
- Red Columbine (aquilegia formosa, Western North America)
- Primula Poissonii (China)
- Rodgersia Pinnata (China)
- Plantain Lily (Hosta sieboldiana, Japan).
Scotland is among the regions having been hit particularly hard by Storm Dennis, with residents evacuated from Hawick and Newcastleton on the southern border and yellow weather warnings issued by the Met Office for the whole of the nation.
Edinburgh is losing the equivalent of around 15 football pitches of green land each year, and much of this is due to private garden areas being paved over or built on, such as for new housing developments.
But urban streets that have had vegetation covered with concrete struggle to naturally drain surface water from adverse weather conditions.
‘Over the last 25 years, Edinburgh lost an average of 11.3 hectares of green land each year to urban creep and urban expansion, said Dr Clare Rowland, an earth observation scientist at the Centre for Ecology & Hydrology.
‘Homeowners have added car parking spaces, conservatories and driveways, or allowed properties to be built in their gardens – all of which have contributed to the loss of greenery.’
The loss of green land increases the risk of surface water flooding, as it creates more surface runoff that can exceed the drainage capacity.
According to the Met Office, the past decade was 8 per cent wetter than the period from 1961 to 1990 on average.
Vehicles make their way through flooding at Dumbarton Quay during storm Dennis on February 15, 2020 in Dumbarton, Scotland
RBGE built its so-called ‘rain garden’ to showcase how effective plants can be at reducing flooding and excess water.
Following downpours last August, it successfully reduced floods on nearby paths and capturing rainwater for the benefit of the plants.
RBGE says its rain garden may influence future planting schemes for coping with climate change.
‘This experimental garden will be helpful in understanding and planning future site management strategies for coping with an unpredictable, changing climate and ensuring uninterrupted provision of the important public amenity at RBGE,’ David Knott, curator of living collections at RBGE.
Measuring 65 ft (20 metres) long by 23 feet (seven metres) wide, the RBGE’s rain garden is a shallow basin that allows water to drain naturally into surrounding ground during heavy rain.
It is located at the lowest elevation of an area known as the Birch Lawn which has suffered historically from waterlogged grass, submerged tree roots and flooded paths.
‘The climate is changing, and in Scotland heavy rainfall is becoming more frequent and intense,’ Mr Knott said.
‘We will be investigating which native Scottish plants, shrubs and wildflowers are best placed to help the rain garden hold and slowly release rainwater into the soil, as well as cope with drier conditions.
‘Not only will the rain garden provide a simple, attractive and wildlife friendly way of reducing flood risk, it will also provide inspiration and knowledge for visitors and other institutions who may need to solve a similar problem.’
HOW DOES GLOBAL WARMING CAUSE FLOODS?
Warmer air contains more water vapour than cooler air.
As more evaporation leads to more moisture in the atmosphere, rainfall intensifies.
This extra moisture is available to storm systems, resulting in heavier rainfalls.
As the US has heated up an average of 1.8 degrees Fahrenheit since 1901, it has also become about 4 percent wetter, according to the NRDC.
Scientists are confident that rising sea levels are leading to higher storm surges and more floods.
Rains were at least 40 percent more likely and 10 percent more intense because of climate change, according to a NOAA study