Drainage channel for vegetable patch and garden: our practical tips

Get rid of standing water for good

Inspirations / How to

25/01/2022

Estimated reading time 5 minutes

Does your garden become waterlogged after the slightest shower? Does your vegetable patch turn into a rice paddy when the autumn rains arrive? If so, the problem is standing water which—unless it is temporary and disperses in a few hours-–cause harm and even kill your plants.

Persistent waterlogging actually alters the fertility of the soil due to lack of oxygen, leading to runoff of nutrients, accumulation of phytotoxic substances, temperature reduction and deterioration of the soil structure. It also damages vegetation, causing germination failure, poor root growth or root suffocation, nutrient deficiency, development of diseases and weed growth. In addition, as you well know, a waterlogged garden and vegetable patch are unworkable.

Today we find out how to reduce the problem of water accumulation in the garden and vegetable patch, explaining how to build a drainage channel.

How to improve rainwater drainage in the garden and vegetable patch

What are the causes of standing water? The contributing factors are numerous, for example soil that has low permeability (because it is not very porous, which is typically true of clay soils), or which is already saturated with water from very intense or prolonged rainfall, the presence of natural obstacles (such as a stony layer in the subsoil) or artificial obstacles (such as nearby waterproof paving). The tendency of water to accumulate can also be due to excessive irrigation.

In case of emergencies, a water pump can help you eliminate standing water, but to address the problem long-term and reduce waterlogging in your garden and vegetable patch it is better to:

  • Build an underground drainage channel (or a network of channels, if the surface area is large) that collects excess rainwater and conveys it downhill to a dispersal point (sewer, ditch or tank of a rainwater harvesting system, so you can reuse it for irrigation).

  • Opt for an infiltration system - a trench or dry well—which captures runoff water and bypasses less permeable topsoil or subsoil to disperse it into the underlying strata, which is more porous.

How to build a drainage channel

The size and depth of the drainage or infiltration system depend on the size of your garden/vegetable patch, the severity of waterlogging, the soil characteristics and the type of vegetation present (whether grass, vegetables, trees or large shrubs).

Here's how to build a rainwater drainage channel:

  • If necessary, clear the area with a brushcutter and prepare everything you will need onsite (you can use a transporter to haul it to the location).

  • Dig the channel using a spade (and utility gloves) or special machinery (trencher).

  • If the ground is not naturally sloping, create a constant 1-2% gradient by digging deeper as you progress (approximately 3-6 cm every 3 m).

  • Lay down a permeable geotextile membrane (i.e. non-woven fabric), making it adhere to the bottom and sides of the trench.

  • Secure the excess geotextile along the edges of the channel using metal pegs, nails or pebbles.

  • Throw in a layer of gravel.

  • Lay a perforated or slotted drainage pipe (drain).

  • Cover the drain with more gravel.

  • Fold the geotextile over the gravel and secure it with pegs (this is to ensure that rainwater seeps through the gravel and drain without them becoming clogged up with earth, roots, etc.).

Finally, fill in the rest of the trench with part of the excavated soil. You can cover the surface of your drainage channel by sowing grass; carpeting it with turf; or alternatively, using gravel or decorative garden stones. In any case, the most important thing is that the surface is permeable, so poured concrete surfaces and cemented paving joints are a no-no.

Likewise, you can build a dispersion trench, which is lined with geotextile, filled with gravel and ideally fitted with drain grating (even without this, the gravel helps with infiltration and runoff water drainage).

Before starting to excavate your rainwater drainage system for the garden or vegetable patch:

  • Check how rainwater management is regulated locally; whether your dispersion system is allowed to drain into a ditch, sewer etc.

  • Identify the critical points where water tends to collect (for example hollows in the ground, downspouts, areas adjacent to impermeable surfaces such as a garden path or wall).

  • Map out the route of your drainage network on paper: choose the shortest route, but pay attention to the subsoil (household pipes and electrical cables, tree roots, very compact soil layers, etc.) and to distances (from the house, neighbouring properties, etc.).

During the works, take photographs to document the location of the rainwater drainage system and how it was built. If water accumulates inside the holes you dig, eliminate it with a water pump: even though water pumps are best used for irrigation, why not find out what else water pumps are useful for?

Earlier we mentioned that standing water can be due to a poorly calibrated sprinkler system, so here are three secrets to watering your garden the right way. Water can cause damage, but it is vital for plants, especially in the warmer months, so here is how to care for the garden in summertime and what to do in the vegetable patch before going on holiday.

How to prevent standing water in the garden

To finish off, here are some tips for preventing rainwater from flooding your garden and vegetable patch. They include preventive solutions for dealing with occasional, temporary waterlogging; and periodic interventions suitable for small areas such as an allotment or flower beds:

  • Level the soil to eliminate any depressions where water could otherwise accumulate.

  • Don’t compact the soil.

  • Work with what you’ve got: grow plants that are tolerant of wet soil conditions.

  • Create a raised vegetable garden by mounding the soil or using wooden planters. Then do the same for the flower beds in your garden.

  • Make the soil more permeable: work it with a rotary tiller or hand tools; add soil improvers to make it more porous (sand and peat if it is clayey); fertilise with manure or compost; adopt the practice of green manuring.

  • Avoid working the soil too intensively, which disrupts its structure.

  • Also avoid the formation of a hardpan due to excessive mechanical tilling.

  • For driveways, parking spaces and so on, if possible favour permeable flooring, such as paving slabs with wide grassed joints, porous block paving with sand-filled joints, or pervious concrete.

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