Why your garden floods and how to fix it

Why your garden floods & What to do about it

Jump too

Garden flooding is commonly caused by poor soil conditions, low points, building in the local area and increased rainfall. Sadly there usually isn’t a cheap way to stop garden flooding.

A French drain and pump solution is usually most effective and costs between £1500 and £3000. 

That being said, there are multiple potential solutions to garden flooding. To understand what the right solution is you need to understand the causes. 

Flooded garden with sandbags keeping in large pool of water

Causes of garden flooding

Poor garden drainage is a common issue in the UK, especially in winter. It can make the garden unusable and even cause damage to plants, paving and wooden installations. Having a waterlogged garden can be as good as having no garden. 

Congratulations, you have started in the right place and asked the right question; “why does my garden flood?

From years of building gardens and installing garden drainage systems, we have built up a good understanding of the causes of garden flooding and garden waterlogging. To come up with a solution which will work, it’s essential to property understand the nature of the issue.

This is a no fluff guide to garden drainage issues to help you work out why your garden floods so that you can put a stop to it. We also have some other helpful tools and guides scattered along the way when you want to move onto solutions. 

Do you really have a garden drainage issue? 

This may seem like a stupid question but it’s worth considering that you may not actually have a garden drainage issue, or at least not one that can be fixed with than localised solution. 

In its most basic form, garden waterlogging and flooding is caused by water failing to leave an area as fast as it comes in.

The greater the difference in entrance and exit speeds of water the worse the flooding will be. Bearing this in mind there are two scenarios which we get called out to but which no drainage solution would be worth using.

Scenario 1: Flooding after a heavy downpour

I’m writing this after a Saturday of wall to wall rain, far more than the average showers we get. This has caused quite a few small floods in gardens and plenty of calls to us to find out what they should do. 

So should you be concerned if your garden flooded? Maybe, but maybe not. If this is an ongoing issue and days or weeks later the ground is still spongy or sodden then yes, you should look for a solution. 

If the water goes away and the garden returns to normal after a couple of days, then no. This is an acceptable normal rate of absorption and is unlikely to cause any real issues.

You could get some French drains installed to redirect the water but it’s unlikely to make a huge amount of difference and in our opinion this solution would cost more than it’s worth if the issue isn’t persistent.  

Or you could look into puddle pumps which can be a cheap, quick solution to temporary garden flooding

Scenario 2: It’s fine in heavy rain but really bad in sustained rainy periods

Scenario two is when the garden is fine or drains quickly after isolated downpours of heavy rain but it gets really bad with sustained periods of rainfall.

This is a sign that the level of your garden could be close to the level of the water table. 

The water table is the level where ground water saturates the soil and sediment, this level will be consistent over a large area of land and probably affects all your neighbouring streets.

What it means in practice is that there is nowhere for excess water to go, in fact groundwater has sometimes been known to bubble up into gardens when the water table gets too high. 

If this happens frequently then the only option may be to elevate the garden or at least a section of it that you would like to be able to use.

Common garden drainage issues

The causes of garden flooding are not always obvious, the more you know about the area and the historic drainage issues the better your diagnosis can be. It’s common that there are multiple causes contributing to the issues so be sure to take all the factors into account when diagnosing the problem. 

The answer to this question will reveal a lot about the nature of your drainage issue: “Has the drainage always been bad or has it been getting worse over the years?”

If your garden drainage has always been bad but doesn’t seem to be getting worse there is a good probability that the main issues are long term issues which don’t tend to change or fluctuate. If the garden drainage has been getting worse over the years then it’s likely that you are victim of some developing issues in the garden or the local area. 

Long term/permanent garden drainage issues

Soil composition

Tire tracks in the mud” by Ivan Radic licensed under CC BY 2.0

Soil composition is something that changes very slowly or not at all. The most common issue with soil composition is heavy clay soil. Clay soil is rich in nutrients but it is very dense so it doesn’t allow water to drain through it well. 

Whether there is clay on the surface or clay just below the surface,  it can cause moderately bad drainage issues in your garden or in a local area. 

Ground elevation

If your garden or part of it is a low point you could be taking water from the rest of the garden or even the surrounding gardens. 

We recently had a call out to a garden which was completely submerged.

They were taking in water from at least four gardens in the surrounding area. 

In this situation  your garden is effectively the drainage for the garden so it can be appropriate to ask for a contribution to any drainage solution you have to purchase.

Water table issues

As mentioned above there could be issues with the water table in your area. These issues are very hard to deal with and you talk to your local council.  It’s probable that there’s nothing that can be done about this issue.

Drainage issues which develop over time 

Soil compaction 

Healthy soil has gaps which allow water to flow through it and drain away.  This transports nutrients and water to plants and allows them space to breathe.

Over years and when soil is walked on (especially when wet), the gaps can be compressed and disappear. The water then has a much harder time traveling through the soil. 

A quick way to fix this is to spike the soil then add lime free sand to improve the spacing between the particles. 

Building in the surrounding areas

Soil, vegetation and trees all hold and store water. Buildings, roads, paving and artificial grass don’t. This means that as areas get more and more build up with man made materials, water has less places to sit and drain away unnoticed. 

As parts of the UK get more an more developed natural water storage gets worse and gardens which were once high and dry begin to flood.

If there has been large scale construction, landscaping or deforestation going on in your area this could be contributing to a growing drainage issue. 

We see this frequently on new build estates as they expand.

The home owners who move in as the estate is still being built quickly see their garden drainage situation deteriorate as more and more houses are put up and lawns are turned into patios or artificial grass areas. 

If this is your issue you will need to find an in-garden solution to cope with the excess water because it’s likely the issues will only get worse as more houses are built and people move towards man made surfaces and away from plants in the garden. 

How to fix you garden drainage issues

There are a few things which you can do to fix your garden drainage issues

Don’t have too many man made surfaces in the garden

Man-made surfaces like paving and artificial grass may create your dream low maintenance garden but they also absorb very little water. Overuse can create run off into other areas of the garden or into surrounding Gardens.

Plant leafy vegetation 

Leafy vegetation such as hedges, perennial shrubs and other common garden bedding plants can store and hold excess rainwater.

Install a garden drainage system

The most effective way to improve your garden drainage is through a well-designed garden drainage system.  check out our useful guide on garden drainage systems or if you are in the Preston area get in touch for a free consultation.

If you want to stop your garden from flooding there may be some things you can do yourself but as we have seen many times over, there is rarely a quick fix for flooding. Most issues require a combination of French drains and drainage pumps due to the sheer amount of water. 

As Amazon associates we earn from qualifying purchases