The effects of waterlogging on lawn
Author: Stefan Palm Date Posted: 27 June 2023
With all the rain around this week, you may have noticed that it didn't drain away as quickly as you might have expected. If water pools on the surface for extended periods of time, you may have a waterlogging problem.
To be honest, I’ve been a bit surprised about the amount of rain we’ve received in the later part of Autumn and into Winter. While we are getting more than average amounts, and it is definitely “wet”, it’s not crazy volumes. I think it’s the idea in the back of my head that we are expecting dryer times ahead.
That aside, in casual observations around the neighbourhood and while out consulting, I have noticed that it isn’t uncommon to find lawns quite soggy underfoot. You can feel the water squelching around in amongst the lawn and soil. In poor drainage situations, soils can become waterlogged, which can be problematic for lawns. Waterlogging occurs when excessive water accumulates on the surface, saturating the soil and preventing proper drainage.
What’s the problem with waterlogging?
Rain like this is expected during Winter, and most lawns are OK with having wet feet for a period of time. Even after heavy rain, you should find that the water dissipates fairly quickly, which is what you want to happen. If you find that water pools on the surface and stays there for more than a day after rain, you may start to experience problems. It’s when water hangs around for longer periods that things start to become messy for lawns. The longer a soil stays waterlogged, the less oxygen is present, and lawns need oxygen to stay healthy. Lawns such as couch, kikuyu and buffalo are reasonably tolerant to short bouts of waterlogging; however, if they are unable to breathe properly for longer periods, you’ll need to take action. Symptoms of waterlogging range from discolouration and patchiness to total death. A lack of oxygen in the soil is often referred to as anaerobic conditions, which can also lead to the build-up of gasses like carbon dioxide and ethylene which are not good for root growth.
When lawn roots in the soil are waterlogged for long enough, they begin to recede and rot. Older lawn blades will turn yellow, and the entire stand will begin to thin out and look brown. If you think it’s a problem in your lawn, cut a 100mm deep core sample from a soggy area. Soils that have been waterlogged for long periods will usually exhibit two symptoms. The soil will have a distinct rotten egg or sulphur-type smell, and you’ll see black layers through the soil profile. If you see these things, then you most likely have a problem to some degree. If you don’t see them, your soil hasn’t been waterlogged for long enough to be a problem for your lawn.
Understanding the Causes:
Before we delve into solutions, it’s crucial to identify the common culprits behind poor drainage in lawns. Understanding the underlying causes will enable you to make informed decisions and implement appropriate remedies.
- Poor Drainage System: Insufficient or improperly designed drainage systems can contribute to waterlogging in lawns. If water cannot escape effectively, it accumulates on the surface, leading to waterlogging.
- Heavy Rainfall: Intense or prolonged rainfall events can overwhelm the natural drainage capacity of the soil, resulting in waterlogging.
- Compacted Soil: Soil compaction reduces the soil’s ability to absorb water, causing water to accumulate on the surface instead. Common causes of compaction include heavy foot traffic, improper lawn maintenance practices, and construction activities.
- Soil Composition: Different soil types have varying drainage capabilities. Heavy clay soil retains water, while sandy soil drains quickly. Finding the right balance is key to achieving optimal drainage.
- Slope and Grading: Incorrectly graded lawns or those lacking proper slope can contribute to water pooling in low-lying areas. Water will naturally flow towards the lowest point, exacerbating drainage issues.
What can you do if you have waterlogged soil?
If you notice that you have water on the soil surface for extended periods of time, I would advise you to consider ways of diverting that water away as there are very few plants that will tolerate waterlogged soils for extended periods. Methods include coring, topdressing and introducing drains.
Coring and topdressing
Coring can help divert water away from the surface. The deeper the core holes, the better. Once the coring is completed, lightly top-dress (to fill the holes) with some coarse sand or gypsum. Be sure not to top-dress heavily in winter - once you've finished coring and topdressing, you shouldn't be able to see any sand on the surface.
If your waterlogging issues are more severe, you may need to consider installing some drains. There are many types of drains available on the market that will allow you to collect and divert water away to your stormwater system. Drains are typically installed in the lowest part of the lawn where the water collects. These include:
Strip drains: Also known as channel drains, these drains are typically installed along the edge of a lawn between the lawn and a path or driveway. They can prevent excess water from draining off hard surfaces onto the lawn
Pit drains. If this is not possible, consider installing a soakage pit. This is where you dig a pit or hole in the low part of the lawn where water accumulates. Fill it with coarse rock or gravel, then put a 100mm layer of soil on top. Water will filter past the soil and into the pit where it can dissipate over time, keeping the water away from the surface roots.
Ag-drain - If you plan on using this sort of drainage system, do some google research first so that you understand how to install it properly. Ag drain should only be used as a last resort and can be used to drain water away from your lawn to another (lower) part of your garden. It can be used to divert water to the road as well but should never be connected to your rooftop downpipes or your general household stormwater pipes. If your ag drain pipes are connected to your general household stormwater system, every time it rains water can flood back into the agricultural pipe and flood the trench that is meant to be collecting water!
Solving drainage issues can be difficult and solutions can be very tailored and unique to your circumstances. If you need any further help with drainage, give us a call on 8298 0555 or send me an email to email@example.com