Garden Drainage – How to Prevent Waterlogging

No one wants to have to dig out their wellies everytime they go into their garden. However, because of the unique weather we’re ‘blessed’ with here in the UK, rain is rarely in short supply. Our gardens often fall victim to a daily soaking and even the most free-draining soils struggle to hold up against the relentless drizzle and showers we’re all too familiar with. Inevitably, soil becomes saturated and the ground waterlogged. Before you know it, your garden resembles a mudpit.

Only the most tolerant garden plants are able to survive waterlogging or flooding as the amount of oxygen available to the roots is significantly reduced; this causes yellowing; root rot; and, in worst cases, kills off otherwise perfectly healthy trees, plants and flowers.

All is not lost though as conditions in your garden can be improved using various techniques to promote drainage and prevent ‘flood’ damage. There are a range of garden drainage solutions which can help remove standing water and in turn, stop your garden from becoming a domestic marshland! Investing in effective drainage can also help prevent problems with damp, both inside and outside your home, reducing the risk of damage to masonry and brickwork.

Only got 5 minutes

We all know the importance of keeping our gardens sufficiently watered however too much water can have just as serious of an impact as not enough. A few steady days of rainfall can turn even the most aesthetically-pleasing outdoor area into a quagmire, and cause all kinds of sinister problems below the surface.

The ground becomes saturated (waterlogged) when rainwater, which has collected on the surface, fails to percolate the soil due to insufficient drainage. It is a common sight in areas of naturally poor-draining soils, or areas where two or more soil types have been combined resulting in compaction.

Knowing when your garden is waterlogged

If we’re honest, how many of us actually know the difference between a wet lawn and a waterlogged garden? The occasional flash-flooding often seen after a heavy downpour is unlikely to cause any lasting damage to plants and turf; saturated soil which is unable to drain naturally is when the most damage occurs.

After a prolonged period of heavy rain, if there’s puddles that don’t appear to be draining, squelching when you walk across turfed areas, and, in extreme cases, the presence of moss or reeds, it’s safe to say you’re dealing with waterlogging!

Other symptoms which may indicate waterlogging include: 

• Discolouration of leaves – yellowing or darkened/brown patches
• Wilting
• Oedema (blistering of the leaves)
• Blue/black, smelly, peeling roots
• Peeling shoots
• Stunted growth
• Death

All of the above symptoms can indicate water stress, whether this be too little or too much water.

With waterlogging, the roots are starved of oxygen meaning they are unable to absorb the water or viral nutrients needed for the plants’ survival.

In order to be sure your garden has fallen victim to waterlogging, a quick test that’s easy to do is to dig a small hole in your garden (about 2ft in depth). Fill the hole with water and leave it for around 4 hours. When you return, if the water hasn’t drained, that’s a fair indication that your drainage may be in need of attention. It’s best to avoid doing the test after particularly wet weather as your soil will be saturated and inevitably, drain slower than usual.

Improving your garden drainage – the best way to prevent waterlogging

• If you’re adding trees to your garden, plant them in slightly raised ground
• Cultivate plants and crops in raised beds
• Choose a permeable surface when hard landscaping
• Consider a green roof (also known as a ‘living roof’) for increased water storage and to decrease flood risk
• Seek advice from a professional with the view to Installing land drains
• Dig a ditch or pond at the base of your garden, ideally at the bottom of a slope
• Plant trees and plants that aid effective drainage e.g. hydrangeas
• Introduce water butts/rain barrels into your outdoor area

Likely reasons why your garden isn’t draining

So you’ve done the test and, after four hours, the water in your 2ft hole is still sitting there. Now, there’s numerous reasons why your garden may be finding it difficult to drain.

Identifying what’s causing the problem is key in remedying the problem.

Reason	Consequence
Uneven surface(s)	Allows excess water to form puddles
Water table is too high	Hinders drainage
Your garden has a hard-standing area such as a driveway, terrace or patio	Impermeable hard surfaces limit natural drainage
Location – base of slope and/or low elevation	Natural drainage is slow
Blocked, damaged of disconnected guttering	The pathway which the flow of water takes away from your garden is blocked/broken – the water has nowhere to go but back.
Underwater springs	After heavy rain, the direction of flow may alter its course in order to deal with the increased volume of water
Neighbouring drainage systems	If mis-directed, water may be diverted into your garden
Building foundations	Houses and gardens that have been built on water-retentive clay struggle to drain easily
Compacted soil	Compacted, dense soil significantly hinders drainage

Why you need to tackle waterlogging

Excess water caused by inadequate drainage not only looks unsightly and is impractical, it causes numerous problems when it comes to plant growth.

Saturated soil limits the supply of oxygen to the roots. The roots are unable to function – they fail to absorb the water and nutrients needed for healthy growth and ultimately ‘drown’. The visible part of the plant above the surface, unable to access moisture or food, discolours and wilts, before dying off completely.

Very few plants can survive waterlogging, particularly during the warmer months when flash-flooding is most common; this is because as the temperature rises, plant roots respire more actively and in turn, demand higher oxygen levels. 

Types of garden drainage solutions

In the short-term…

If the worst happens and you’re faced with a heavily waterlogged garden, you’ll need to get to work quickly in order to try and limit the damage.

Step 1: Identify the source of the water – not all waterlogging is caused by excessive rainfall. Groundwater flooding or burst or blocked drains may also be to blame. 

Step 2: Wash down any hard surfaces and collect up any debris to prevent any further blockages. It’s advisable to wear gloves and overalls if there’s a risk the water may have been contaminated with waste or pollutants.

Step 3: Keep pets and children off saturated soil

Step 4: Remove any visibly damaged shoots from affected plants

Step 5: Discard of any edible crops affected by the flood

Step 6: Check the pH level of the soil and apply suitable fertiliser/compost to improve soil structure and aid plant growth

Step 7: Bizarre as it sounds, be sure to water plants thoroughly during subsequent dry spells as after the trauma of waterlogging, plants become increasingly vulnerable to drought stress

Once you’ve gathered your thoughts and the waterlogging seems to be subsiding, you need to start thinking about prevention. It’s highly likely that if your garden has fallen victim to waterlogging once, it will happen again.

In the long-term…

Garden drainage – ditches explained

The simple ditch

Very few gardens are perfectly flat: most do have a varying gradient. At the lowest end of the garden, dig a ditch around 3ft deep. The sides of the ditch should ideally be sloping. As the name suggests, this method of garden drainage is somewhat basic, however, is often all that is needed to improve most domestic garden drainage issues. 

The French ditch

Similar to a simple ditch, the French ditch is dug at the bottom of a slope, however it should not be as deep, ideally only needing to be around a foot and should not be left ‘open’.

1. Dig the ditch along the length of the base of the slope.
2. Line the trench with polypropylene (or other porous landscape fabric)
3. Pour a thin layer of gravel into the ditch, over the fabric, and fold the remaining fabric loosely over the gravel
4. Add more gravel on top of the fabric 
5. Cover the gravel with topsoil 

Land drains

Similar to the French ditch, land drains also involve digging out a sloped-sided ditch around 30cm deep, lining it with landscape fabric, and filling it with gravel. The difference is that you will be fitting plastic or corrugated land drain pipes inside the ditch.

Whereas the simple ditch and French ditch are fairly easy to dig out, when it comes to installing a piped drainage system, it’s worth seeking the advice of a professional; the last thing you want is to be misdirecting the water, or not fitting the system correctly, and having to dig the whole thing up again a few months down the line. 

Garden drainage – slitting/spiking explained

Spiking or slitting the surface of compacted soil using a specialist lawn spiker tool or a standard garden fork can improve the drainage of a garden prone to waterlogging. The deeper you’re able to spike, the better (ideally around 10-15cm). Once the compacted soil has been penetrated, fill the holes with a permeable substance such as sand or a nourishing topsoil, allowing rainwater to percolate freely to deeper, less-compact soil.

How to prevent waterlogging by caring for your lawn

Nourishing your lawn with a good-quality fertiliser during spring not only helps the grass to recover from winter, but also encourages the growth of a resilient, healthy root system. Applying a phosphorus-based fertiliser later in the year – ideally in autumn – will continue to promote and support strong root growth.

It’s also worth keeping an eye out for moss, particularly during the cold, damp months, as this can literally ‘smother’ the grass and serve as an unwanted obstacle for surface water to have to percolate. To support the healthy growth of your lawn, moss should be removed by using a specialist moss killer prior to scarifying, and disposing of appropriately.

Alternative garden drainage solutions

Although a waterlogged garden looks unsightly, more often than not, it’s relatively easy to salvage. Taking the time to investigate the source of the problem, and understanding to what extent your current drainage is failing, will allow you to implement the most appropriate drainage solution.

Understandably, for minor waterlogging cases (e.g. a lawn that feels a bit spongy underfoot or the odd puddle of standing water) you may think going to the effort of digging ditches or laying pipe drainage is excessive. There are alternative garden drainage solutions you can try which may be able to solve the problem less invasively.

Alternative solution	Details
Plants to help with garden drainage	Certain plant types can actually help to regulate soil moisture levels. Hydrangeas are a popular choice for wet soil types, whilst geraniums and fuschias work well in clay soils.
Rain barrel/water butt	Can be distributed randomly or used to collect rainfall from the downpipes of outbuildings. Good for the environment as the water collected can be recycled and used to wash cars or water plants during warmer conditions.
Guttering on outbuildings	Outbuildings including sheds, garages and greenhouses often do not have guttering. Fitting plastic guttering is inexpensive and  simple to do but is effective at directing excess water to rain barrels.

Frequently Asked Questions