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How to reduce surface water flooding
Minimise water build up and potential flooding
Whilst most of us understand the risks that come with river flooding, the risks associated with surface water flooding are less well-known.
What is surface water flooding?
Potentially able to impact all of us, surface water flooding happens when water is unable to drain away from the surfaces it has fallen, or flowed, on to.
It can appear as large puddles, water sitting on paved surfaces outside our homes or flowing water.
What causes surface water flooding?
Heavy rainfall is the main culprit. However, surface water flooding can also occur after heavy snowfall when the snow and ice starts to melt. It can also happen when more rain falls after a prolonged period of wet weather – the rainfall itself might not be significant but it’s just enough to tip existing water levels over the edge.
Normally, if rain falls onto a hard surface, like roof tiles or concrete, it will roll away and seek the nearest drain. If it falls onto grassy surfaces, planted areas or bare earth it will be absorbed until the land is saturated.
Surface water flooding happens when water that has fallen onto a hard surface cannot roll away or find a drain. It also happens when water falls onto a vegetated or soft surface that is already saturated so it can’t soak up any more water.
What problems can surface water cause?
When surface water flooding occurs in your garden, it can;
- Create a hazard on paved surfaces with standing water and puddles, as well as slippery moss growth if water sits for a long period of time
- Smoother submerged plants and lawns, either killing the vegetation or causing long-term damage
- Cause structural problems for paved surfaces, fences, sheds and outdoor buildings if they experience prolonged periods under water
Both surface water flooring and river flooding can have immediate and damaging impacts on your home. You can find out more about how to protect your property and family in our guide to protecting your home from flooding.
Thankfully though, there are plenty of simple steps you can take to help rainwater reach the ground beneath us as well as slow its flow. Not only will it help to reduce surface water flooding in your garden, it will benefit your home and neighbourhood too.
In this article, we'll talk you through actions you can take with;
- Houses, garages, sheds and other outdoor buildings
- Patios, paths, parking spaces and other hard surfaces outdoors
- Lawns, beds, borders and plants outdoors
These can all be taken before bad weather arrives, so that you can rest assured once rain starts to fall.
Top tips to reduce surface water flooding
Houses, garages, sheds and other outdoor buildings
Clear gutters and outside drains
Gutters play a key role in channelling excess water away from your home. Regularly check that they’re in good repair and replace any parts that have deteriorated or broken. In the spring and autumn, clean your gutters using a bristle brush or a tool designed specifically for the job and remove the debris – don’t be tempted to try and wash it down the drain. This will help to remove loose leaves and debris that can block downpipes, preventing water from draining away.
You can also fit gutter guards to help stop material like this entering your gutter in the first place – they make life a little easier if trees overhang your home.
The downpipes from your gutters should run into a drain or soakaway (a hole filled with loose gravel or stones that is intended to help water soak into the ground). If yours flow straight on to a paved area or driveway, consider adding or moving gutters and downpipes to make sure that water flows safely away to an area where it can’t collect on a flat surface.
Keeping your gutters clean and clear will also help to prevent overflows which can cause damp patches on the walls of your home.
Make sure roofs are in good repair
Keeping an eye on your roof is an important part of protecting your home from heavy rain and snowfall. Rainwater will rely on a smooth, sloped surface to find its way into the gutters and down pipes that’ll help it to flow away from your home. Tiled roofs should be checked for loose tiles at least once a year as well as after extreme weather, with repairs made as soon as possible if any tiles have become loose or damaged. Pay close attention to any flat or felted roofs – common on garages, porches and single storey extensions. They’ll have been built with a slight slope to the surface to allow water to drain away easily into gutters. However, they are especially vulnerable if they become damaged and can let water into your home and prevent rainfall from draining away.
Repairs to flat roofs should be undertaken by a qualified professional who can advise on the best solution for your home. However, felted roofs can be easily replaced using high quality roofing felt and just a handful of tools. Summer is the best time of year to tackle replacing the felt on a shed roof or similar, but repairs can be made throughout the year if necessary, provided the surface below is thoroughly dry.
Small cracks and gaps on flat roofs can be fixed in the short term with emergency roof sealant. It’ll help to keep your home weather tight until full repairs can be undertaken.
You can find step-by-step guidance for felting a shed roof in our guide on how to build a wooden shed.
Use water butts to collect rainfall
If it’s difficult to configure your guttering so that run-off is funnelled towards a drain or soakaway, it’s a great idea to make good use of it by installing water butts at the base of your downpipes. They’re ideal for capturing water for outdoor use – such as watering your plants – but can also help to manage the flow of water off your home. You might want to consider installing multiple water butts in different locations or linking several together to provide plenty of water storage for the warmer months. Keen gardeners might find it handy to have one in both the front and back gardens to save carry watering cans too far.
Don’t forget that you can install guttering and water butts on garages, sheds, greenhouses and other outdoor buildings. It’s another great way to capture more water to use in the garden as well as minimise the impacts of heavy rainfall.
Find out more in our guide to installing a water butt.
Patios, paths, parking spaces and other hard surfaces outdoors
Choose driveway surfaces that allow water to flow
Driveways and parking spaces can be one of the trickiest spaces when it comes to surface water. Whilst it makes an ideal surface for your car, paving these areas with concrete, asphalt or block paving (pictured) can make it hard for water to soak away. Thankfully there are several options which help to channel water away from your home.
b) Alternatively, lay paving slabs or block paving on top of a compacted hardcore (also known as aggregate) sub-base rather than a concrete base. This will let water flow between the slabs and into the ground.
Plan patios, paths and decks
If you’re planning to construct any new paved areas or patios, choose surfaces that allow water to permeate through, or run easily off them. In addition, take into account that the surface will need a slight fall, or slope, to allow water to drain away from your house and any outdoor buildings.
Decking is an ideal choice for outdoor seating and dining areas as rainwater can flow underneath and into the ground. Making sure that there is a fall in the construction means surface water should run away easily.
If you do opt for a paved surface;
a) Lay a hardcore (aggregate) sub-base rather than concrete slab below.
b) Plan drainage carefully so that rainwater doesn’t flow into the sewerage system (your water company may charge you for this). Include a soakaway in the design to ensure water has somewhere to go. A soakaway is a simple and easy option – simply dig a hole at the lowest point of your paved area and fill with pebbles or loose gravel.
c) Consider mixing up your patio with areas of gravel, shingle and planted areas as well as paving slabs (pictured). Not only can this look attractive, it also offers more drainage opportunities and the chance to bring more vegetation into this area of the garden.
Keep drains clear
It’s not just gutters that need to be kept clear to keep water flowing, you’ll want to check any uncovered (storm water) drains in the spring and autumn and after big storms. Pop on a pair of work gloves (preferably waterproof) and lift out any clumps of leaves and debris and either compost these or dispose of them appropriately. Don’t be tempted to try and wash any blockages away using a pressure washer, as this can cause problems further down the drain.
Once your drains are clear, install a drain guard to help keep leaves out and save you from hard work in the future.
Lawns, beds, borders and plants outdoors
Maintain healthy and level lawns
A healthy lawn does a great job of allowing rainwater to flow through the water table. To help it do its best, keep on top of maintenance throughout the year. Re-seed bare patches to help avoid soil being compacted by heavy rainfall – this can impair its ability to absorb the water.
If you’ve ever noticed water collecting in certain places on your lawn and forming puddles, it’s likely that this is because your lawn isn’t level. During the summer when your lawn is dry, seek out these spots and fill holes with a light mixture of sand and top soil. Then, rake and lightly compact for a level surface. If it’s a large area, you might want to strip the turf off the surface first and replace on top. Smaller patches can be sprinkled with a little lawn seed.
Finally, don’t forget that a turf lawn will do a better job of helping surface water to drain away and be absorbed into the land than an artificial grass one. If you use a grassed area for parking, combine turf with stabilisation mats to provide a surface that's durable. These will allow water to flow through them but also stop grass being churned up by car wheels or becoming compacted.
Plant a variety of leafy vegetation to collect rainfall
Plants and trees play an important role helping to intercept rain before it hits the ground. Large leafy plants, shrubs and trees scattered throughout your garden will absorb groundwater through their roots and catch some water on their leaves. They’ll also help to shelter bare ground, saving it from damage from intense rainfall. The species, or type, of plant isn’t too important – everything from fruit trees to garden palms, hedges to ornamental shrubs can play a part. However, it is worth including low maintenance evergreens in the mix, as these will remain leafy throughout the year.
Look for opportunities to add more plants in unexpected spaces. Low-maintenance, evergreen shrubs can make a colourful addition to even the smallest front garden. Even potted plants and containers can help – just try to use the largest pots you can for maximum benefit.