How to Use Swales for Storm Management in Your Yard

Sometimes too much water is not a good thing, such as when it's overrunning your yard and creating problems. When this happens, the use of swales to divert water is a project you'll want to consider.

What is a Swale?

Consider a swale a tool used much like your garden hose, but by building a small trench. It is used for irrigation by redirecting excess storm water runoff to provide moisture to your garden and landscaping, eliminate pooling water, improve soil quality, and reduce soil erosion.

When a swale is created properly, it allows you to be environmentally friendly by using water versus allowing it to just drain off, taking all the nutrients and soil along with it to a localized pond or overly saturated area of your yard.

Purposes for Creating a Swale

Creating swales that function properly in the management of runoff water is important for several reasons. Along with recycling water for irrigation purposes, swales help protect your property from flooding during the rainy season and melting snow/ice during the winter. It also provides a supply of water and nutrients to areas that may experience drought situations in the drier months.

Creating a Swale

Digging holes for a trench in yard

There are no set-in-stone rules about how large or small a swale must be. It can be any size. It can also be any shape that is on contour or pitched to suit the needs of your property.

When choosing where to place a swale, several things are important. One is to consider the gradient so that it isn't too steep, which can result in excess mud sliding down the slope that can harm the property. Another is placing the swale at the highest-level point to capture the water run off, but not too high. Lastly, to be effective and provide water to a wider range, you'll want the swale to be as long as possible.

It is imperative that the swale system be placed in an area or areas that will have access to an abundance of water runoff during a rainstorm.

How a Swale and Berm Operate

When a swale is dug on a sloping piece of land, the soil is placed on the downhill side of the trench. In other words, the soil is placed beneath and along the length of the swale. This soil is referred to as the "berm." It is an important part of the swale creation as it is used to plant trees whose roots will help maintain the soil's stability along the trench. You can also plant vegetables, flowers, plants, herbs, etc. as they will benefit from the water source, but trees are especially vital.

The berm is rich in nutrients that will stay hydrated, making it an ideal location for growing deep rooting plants such as strawberries that will help keep the topsoil stable. You may also consider planting a ground cover species to help prevent the soil from drying out, keep weeds at bay, and add nutrients back into the soil.

Whatever you choose to plant, it needs to be done immediately before the soil has an opportunity to dry out and erode. While the soil is still fresh and pliable is the opportune time to set plants, vegetables, trees, and ground cover in place.

As rainwater runs down the slope, it accumulates in each of the swales where it will slowly seep into the ground providing much needed moisture for the property. As noted above, the longer the swale trench, the more range the water has as it is absorbed at an even rate into the land beneath the trench.

A small pond in a yard

Swale Tips

It's a good idea to consider having a designated spot where passive overflow from the swale can drain into, such as a pond. Also, once the swale is created and level, add a layer of mulch. As water accumulates in the swale and drains into the ground, it will carry nutrients from the mulch along with it. Mulch will also help deter evaporation within the swale. When the swale is not filled with water, the mulch-lined trenches serve as access paths to your property.

Instead of allowing ample amounts of rainwater to drain into the street or cause overly saturated areas in your yard, consider using swales to manage the natural resource to your advantage.