Solutions for a waterlogged garden

Conventional subsoil drain

Trenching and piping provide a good solution to most drainage problems in the garden. Subsoil drainage systems are installed underground to remove excess water from the soil and direct it elsewhere.

 

To construct a conventional subsoil drain, you will need to dig a trench about a spade width wide and about 30-40cm deep. 

The trench can be lined (or pipes wrapped) in geotextile material to prevent soil from clogging the pipe. A high density polyethylene (HPDE) pipe is then placed inside the trench on a bed of gravel stones.

 

Once the pipe is in place, the trench is then backfilled with sand. Geotextiles are permeable fabrics that allow water to pass through them but filter smaller sand particles to stop them clogging the pipes.

 

Plot the course of your trenches before you start digging. This is important to ascertain where the water will daylight (the place where the pipe ends and pushes the excess water up to the ground level).

 

Trenches shouldn’t slope too sharply but should allow water to trickle away slowly. Aim for a 2% gradient, about 10mm per 1m of trench.

 

If you can’t daylight the drain on or beyond your property, you can create a ‘soakway’. This is a hole (about 1m by 1m) and around 80cm deep.

 

Fill the hole with gravel and lead your trenches into this hole. The soakaway will keep the water contained until it drains away. More than one soakaway may be required if you are dealing with a large amount of water.

 

Soakaways are effective if your garden slopes away from the buildings on your property.

 

Kaytech offers several products that can be used to construct a conventional subsoil drain.

 

Trenches can be lined with a bidim® filter jacket, a nonwoven, continuous filament needle punched polyester geotextile.

 

For piping, Kaytech supply Flo-Pipe®, a HDPE pipe consisting of a ribbed outer shell combined with a smooth inner core.

 

For areas with high flow, consider Geopipe®, a lightweight HDPE extruded drainage pipe, that has 70% of its surface area covered by an open lattice.

 

Alternatively, you can use a fin drain like Kaytech’s Flo-Drain® to lower a high water table or intercept seepage in different applications.

 

In residential gardens they can be used in courtyards, along embankments and along the edges of driveways. They replace the use of stone in conventional subsoil drainage and are simple to install.

 

While trenches are deep, they don’t have to be very wide. In the construction of a fin drain, a section of prefabricated geotextile is placed vertically down the trench wall and a secured around a suitable HDPE pipe.

 

Flo-Drain® is supplied preassembled and the Geopipe® is positioned at the base of the fin. The geotextile flap must be firmly secured around the pipe and joined by means of wire twine. Backfill must be well compacted in layers and be a well-graded, free-draining material.

 

Guttering, downpipes and rainwater pits

Your roof channels an enormous amount of surface water and you need to make sure this water does not end up near the foundations of your home.

 

Guttering and downpipes should be correctly fitted and properly maintained to ensure that water is directed correctly away from the house.

 

Rain barrels or rainwater harvesting tanks can be positioned at downpipes to harvest rainwater. This can be stored and used to irrigate the garden at a later stage or during the dry season.

 

RainDrain from Seaqual is a rainwater pit manufactured in colours that blend into the surrounding paving or even your lawn. It eliminates the need for brick cement sumps.

 

RainDrain can be installed below external rain gutter downpipes. RainDrains can also be used in association with water harvesting systems by connecting them together with underground storm water pipes which can feed into underground rainwater tanks.

 

Filter your water by placing either a filtration mesh or a porous sponge directly inside the body of the RainDrain. The drain does require occasional cleaning to prevent blockages. RainDrain is an all-South African product.

 

Permeable paving

Permeable paving can effectively manage run-off on paved surfaces. It almost immediately absorbs rainwater and storm water that falls on it.

 

Permeable paving also allows air to pass through the provided voids. This ensures that the ground breathes naturally by thermal action, supplying oxygen to roots and to aerobic bacteria.

 

Water can also be collected underground and pumped for use in a surrounding landscape. With permeable paving the water is filtered directly upon penetrating the paving instead of traveling along roadways and collecting dirt and pollutants and depositing these into waterways.

 

The concept of permeable paving is relativity new in South Africa, but has been used in Germany, the European Union, USA, Australia and other countries for many years.

 

Vanstone’s Aqualock Pavers are specially designed to have strong interlock and openings to let the water through.

 

Vanstone now offers three new permeable concrete block pavers called Aqualock Pavers in 60mm and 80mm thick and the Aqua Random Pavers which are 50mm thick.  

 

Bog garden

If you have a waterlogged flowerbed that isn’t against your home, you can turn it into a bog garden to utilise the excess water. The site should also receive about four to five hours of sunlight each day.

 

To start off, you’ll need to excavate a hole, about 45cm deep and as wide as you would like your bog garden.

 

Line the hole with pond liner. Press down firmly, but make sure at least 15cm of the liner is exposed at the top of the hole. This will allow for settling of the bog.

 

Puncture drainage holes in the pond liner. You can use a garden fork at intervals of 1m. This is important to prevent the bog from getting too wet.

 

Bog plants like plenty of moisture, but they can rot if they are allowed to stand in too much water and compacted soil.

 

Place a length of porous pipe in the bottom of the excavated hole, on top of the pond liner. If you have a piece of hosepipe (with plenty of holes), you can use that.

 

Seal one end of the pipe and make sure the other end comes up out of the hole. You can irrigate the garden through this pipe when necessary.

 

Now cover the bottom (over the pipe) with a 3-5cm layer of gravel or stones. Backfill the hole with a mixture of soil, coarse sand, peat and well-rotted kraal manure.

 

Allow to settle before selecting and planting your bog plants. After settling, any exposed pond liner can be covered with rocks and plants.

 

You can also turn an old unused garden pond into a bog garden, or create one alongside your existing pond

 

Sources

Kaytech, 011-922-3300

Seaqual, 044-382-3484

Vanstone, 012-541-2056

 

Read this first article to see the common causes of poor drainage