Levelling for garden drainage

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When it comes to solving garden drainage problems many instantly think of expensive drainage systems and pump installations.

However in my 20 years experience of resolving landscape drainage issues the solution is often something much simpler. Most garden drainage problems occur due to a sites surface levels. This could be the levels and gradients of the garden itself or surrounding properties.

A gardens ground level should allow excess water to naturally flow from your highest boundary to your lowest boundary. This is how landscapes have naturally drained for millennia.

​The problem arises when manmade interferences and installations block and trap water. Here I will summarise the importance of levels and how they can be improved for efficient garden drainage. 

​Assessing existing levels 

​If you are encountering garden drainage problems one of the best things you can do is assess your surface levels. Ask yourself the question; is standing water or boggy areas in low spots?

Are surrounding properties higher than yours causing water to run to the lowest point? Are nearby installations increasing surface run off or trapping water within your property? Most of the time answers to these problems will probably be met with a ‘yes’.

Consequently you will need to assess your surface levels. Mark out all of the worst effected boggy and saturated areas in the garden. 
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Then analyse your site from multiple directions try to work out the lie of the land. You can use tight string lines and laser levels to get a picture of your sites high and low spots.

The best way to solve garden drainage with levels is to realise a flat and level ground plain. If your garden is on a natural slope, a flat and flush soil level should be laid to that gradient.

​You want your new flush and levelled garden to fall to your lowest garden boundary. Below I will list and explain the individual processes involved in garden levelling for drainage. 

​Alleviating compaction

A very typical characteristic of boggy gardens is excessive compaction. This is especially so in low spots that collect water in times of heavy rain.

Moist soil compacts extremely well underfoot leading to more compaction and more water pooling. The result is a continued cycle of compaction and standing water.

​Therefore before levelling your site you will need to de-compact your subsoil. 
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This is best achieved with an excavation machine and a ripping hook. This strong metal attachment rips deeply into the ground breaking up compacted subsoil.

​Such action will allow surface water to percolate your underlying ground once again. Alternatively, you can dig your soil over deeply with a digger bucket or by hand on smaller areas. 

​Amelioration for better drainage

Soil amelioration is often known as improving a soils structure and fertility for plants. However, soil can also be ameliorated for the sole purpose of improving drainage.

​In most cases this involves adding sharp sand and organic matter to help break apart soil particles. This creates tiny air spaces within the soil allowing it to drain easily. 
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After digging a compacted area deeply sharp sand and organic matter such as compost can be added. For best results add a 70mm layer of each and spread them evenly over the soil.

​Then you can Rotovate the soil well with a tiller machine to mix the soil well. When the ground has been worked to a fine texture it can be re-levelled. 

​Spreading high areas into low areas

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One of the most effective ways to level your soil is identify both high areas and low areas. This can take a keen eye but you can use a tight string line to help you.

You can level your soil with a landscaping rake, long handled shovel and wheelbarrow. Pull the high areas into low areas until you reach a level and even surface. 
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​Installing level retaining edging

​One of the best ways to create perfectly level soil is by installing retaining edging. Edging such as bricks, blocks and metal edging can be installed perfectly level around a new lawn or gardens perimeter.

These are particularly useful if you want to raise your soils level for improved drainage. Once such edging has been installed topsoil can be spread flush and evenly to the top of the edgings.

​This will provide a new even level to your garden with no low spots to collect water. 
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​Spreading free draining layers

​Free draining layers are layers of sharp sand under the surface which draw excess water from the surface. These are typically spread under new lawns to prevent them from becoming boggy.

​They are particularly useful on lawns with an underlying clay soil. Once underlying clay is ameliorated and spread level a 30mm layer of sharp sand is spread on top. 
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​This acts as a base for a further 30mm layer of topsoil on top to lay the new lawn. As well as improving drainage the dense sand layer prevents the clay seeping up and saturating the topsoil.

​This creates a new level lawn that is not susceptible to flooding and bogginess. 

 Thank you for reading our article on levelling for improved garden drainage.

If you require garden re-levelling or garden drainage services do not hesitate to contact us.

Based in Amersham, Buckinghamshire we undertake a whole range of garden landscape services. Contact us here.

If you would like to read more of our garden drainage articles I will link some relevant topics below. 

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