- Landscape Swale Guide: How to Landscape Drainage Swales
- How to Landscape Drainage Swales
- Table of Contents
- What to Avoid When Landscaping Drainage Swales
- What is a Permaculture Swale?
- Is a Permaculture Swale Right For You?
- Why a Permaculture Swale Could Be Helpful in Your Yard
- Water management is the foundation of a low maintenance landscape.
- How to Build a Bio-Swale (and Why You Should Want To!)
- Step-By-Step Instructions
- Step One: Mark It
- Step Two: Dig It
- Step Three: Plant It
- Swales, Berms & Mycelium – Edgewood Gardens’ Permaculture Paradise!
- Swale Landscaping Benefits
- What is a swale and why build one on your property?
- The many benefits of swale landscaping
- Before you start to dig a swale
- A swale as part of your landscape design
Landscape Swale Guide: How to Landscape Drainage Swales
How to Landscape Drainage Swales
Table of Contents
What is a Drainage Swale?
Can I Fill a Swale to Level it Out?
Can I Dig a Swale?
What to Avoid When Landscaping Drainage Swales
How To Landscape Drainage Swales
What is a Drainage Swale?
Let’s start with the dictionary definition of swale, which is — according to Merriam-Webster — “a low-lying or depressed and often wet stretch of land.”
- Guide water away from homes and roadways
- Direct water to gardens
- Prevent flooding
- Capture rain water for reuse
Swales can be part of an area’s natural landscaping, or they can be created to help ensure proper drainage, minimize runoff or capture storm water. In simple terms, they are generally shallow ditches that have gently sloping sides. Depending on their function, they may run along the contour lines of a hillside and may have a berm on the downhill side of the ditch. They rely on gravity to move water and are designed to direct the water where we want it to go.
In areas that receive more annual rainfall than we do here in sunny Southern California, swales are considered a more efficient way to capture rainwater than rain barrels. They are a popular choice among eco-minded homeowners in these areas who use them to direct water to flower or vegetable gardens, to limit runoff, and to trap silt and pollutants in surface runoff.
Locally, swales can be used for this purpose, but they are more often an integral part of the drainage plan for residential, commercial and municipal properties. More commonly referred to by laypeople as ditches or gutters, swales are often found along sloping driveways, adjacent to roads and parking areas, incorporated into golf courses, winding along the contours of hills on farms and in backyards, or along curbs to guide water away from roadways and into storm drains. The primary purpose of most swales in dry climates is to protect structures and to slow down or divert water.
While it might seem like our drought-prone state would not need much in the way of excess water management, drainage swales are a critical part of flood prevention and help keep our ground water cleaner. And even though we do not get as much rain as folks who use swales as part of their irrigation system in wetter climates, we can still maximize our use of the rainfall we do receive by strategically including swales in our landscape design.
Can I Fill in a Swale to Make It Level with My Lawn or Other Landscaping?
The short answer for this one is no.
Some homeowners consider swales unsightly and would rather have a nice, level lawn or a smooth surface along their driveway. The issue is, a manmade swale on your property was put there for a reason, and natural swales are serving a necessary water-carrying service as well, or it would not have naturally formed.
If you really hate the look of your swale or would like to landscape your yard in a way that does not easily accommodate an existing swale, you may have some options available to you.
For example, if you have a swale on your property that is no longer necessary because your property’s drainage plan has changed, you may be able to fill in your swale. It may also be possible to create another swale in a less offensive location to make your current swale obsolete. Depending on your particular situation, it may also be possible to install a French drain, which many people find more attractive.
The most important thing to keep in mind is that swales serve a very important purpose, and no homeowner without an engineering degree or years of experience in grading and groundwork should mess with the swales on their property without calling in the professionals.
Also keep in mind that a swale on your property might not necessarily be protecting your home; it might be there to prevent runoff from your yard from entering your neighbor’s property and causing damage to structures. So just because it looks like the hillside in your backyard is sloped in a manner that does not put your home in danger, this does not mean that the swale directing water coming from that hillside is not necessary. That swale could be saving your neighbor’s house from flooding and saving you from a lawsuit.
Can I Dig a Swale to Direct Water on My Property?
You can add a swale to your property, but — again — you really should not do anything that changes the drainage on your property without the help of professionals.
Landscape architects, engineers and contractors who specialize in grading and groundwork can survey your property and determine the best ways to enhance drainage and direct water while keeping structures and landscaping safe, making sure you abide by local ordinances and ensuring that your neighbors will not bear the brunt of poor drainage decisions.
Additionally, governmental agencies are getting more serious about any type of residential or commercial landscaping changes that could affect groundwater. This means that you may need a permit or there may be ordinances with which you must comply aside from those already tied to your property’s drainage plan.
If you work with professionals, they can also help you make sure you comply with any laws or ordinances affecting your property. If you have existing landscaping, you may be able to work with your landscape architect to add a swale to your current design.
If you are in the process of designing your landscaping from scratch and have sloping areas in your yard, work with your landscape architect to ensure swales or other drainage options are included to divert water away from outdoor living areas and structures and to incorporate these drainage options into the design as seamlessly as possible.
What to Avoid When Landscaping Drainage Swales
Before we dive into some of the many options you have when landscaping swales, we should first address a few things to avoid.
Most importantly — and, hopefully, obviously — you do not want to introduce anything to the swale that will impede the flow of water.
For example, if you need to put a solid fence across a swale, you need to make accommodations to allow the water to flow either below or through that section of fencing unobstructed.
If you have swales with berms, trees can do quite well when planted on the berms or below the swale, but should not be planted in the swale, since this can also impede water flow.
If you plan to plant inside the swell, you will need to be careful not to significantly change the grading, unless the swale is now obsolete, and your intention is to fill it.
While it may seem like these utilitarian trenches are completely unusable or impossible to landscape in an attractive way, swales actually provide some great landscaping opportunities, including some that are particularly well suited for drought prone areas.
Here are just some of the options you can consider for attractively landscaping your swales:
1. Natural Grass
If you have one or more swales running through a natural grass lawn (and plan on keeping your natural grass), seeding or laying sod in your swale is a great way to quickly landscape it and make it less noticeable.
If the sides are not particularly steep, this is an easy option that can enhance the visual appeal of your yard, but you will need to make sure children and pets can safely use the area, since the similar appearance could mean that they will not notice that the ground is not level.
2. Artificial Grass
If you have a swale running through an area where you would like to install an artificial grass lawn, this should not be an issue. Talk to your landscape designer or synthetic turf installer about your particular situation to make sure this is a good choice for you.
Artificial grass is a great choice for sloping areas and can be used to help control erosion, so it is an easy choice for the sloping sides of swales. Again, the similar appearance may make it difficult to see that the ground is not level so supervise pets and children to ensure their safety when playing around the swales.
This is one of the most common choices for swale landscaping, and it is a great way to manage runoff, limit erosion, slow water flow and allow rainwater to more efficiently infiltrate into the soil.
Gravel is also an attractive option that is inexpensive and can be used in just about any situation, which makes this a good choice for most homeowners. However, it can give your swale an even more utilitarian look and can emphasize that you have a swale running through your landscaping.
Turfstone pavers are a type of permeable paving stone that can bring stability to gently sloping swales.
The lattice-like design allows you to plant grass or other living ground cover options in the open spaces, or you can fill these spaces with gravel. This durable, attractive option can help you avoid runoff and erosion and can help filter water as it infiltrates the soil.
Homeowners who choose this option for their swales often appreciate the visual appeal of grass or other living ground covers but want to avoid erosion on the sides of their swales and may want to use their swales for other purposes — such as walkways.
5. Create a Walkway
Shallow swales, or even deeper swales with wide bases, can be used as seasonal walkways in arid climates. In areas like Southern California where our swales are usually dry, we can design swales as multifunctional landscaping features that serve as water management systems and as walkways. As long as you do not impede the flow of water, you can line your swale with gravel and place stepping stones along the base to create a walkway.
Alternatively, in a shallow swale, you can install a durable, attractive, paving stone walkway. Mulch, bark, wood chips and similar walkway materials are not as good of an idea, since they will wash away with a heavy rain and could end up in storm water drains.
6. Design a Dry Creek Bed
This one is really where I think most Southern California homeowners will find the most inspiration.
The movement towards xeriscaping and other drought-tolerant styles of landscape design definitely have most of us using more rocks, gravel and native plants in our designs. Swales are particularly well suited for this type of landscaping, especially if you are interested in including a water-free water feature in your yard.
Dry creek beds are increasingly popular these days, particularly because they bring the look and feel of a water feature into your landscape design without actually wasting any water in the process.
By using river rocks of various sizes to create what looks like a natural creek bed, you can bring an entirely unique look and texture to your landscaping design to enhance the overall visual appeal of your yard, while maintaining the function of your swale.
7. Plant a Garden Along the Edge
If your swale has a berm, this is a great place to plant flowers, trees or a vegetable garden. If not, you can plant along the sides of the swale to take advantage of soil moisture that will be present whenever the swale is performing its primary function of capturing and directing water. As the water seeps into the soil, it will hydrate your plants, which allows you to save water — at least when it rains.
Drought-tolerant, native species are the best bet and the most environmentally responsible choice, particularly due to our lack of rain, which means you cannot rely solely — or even primarily — on your swale to water your garden.
8. Plant a Rain Garden
Our constant state or drought may make a rain garden seem like an idea better suited for our friends in the Pacific Northwest, but small swales, such as those that move water from house gutters to drains or dry wells, can make great rain gardens.
Once established, native plants can do well with little water between rainfall, which makes rain gardens with native species a possibility for Southern California homeowners.
As it is central to life on Earth, so water is of crucial importance to the permaculture plot, providing the plants, livestock and wildlife with an essential element for their survival and growth. Water is also a finite resource. It is precious and should be treated as such. Therefore, permaculture design seeks to preserve and use water in the most sustainable and efficient ways. This includes harvesting rainwater, mulching and composting soil to help prevent excess evaporation from the surface, planting native species that are adapted to the rainfall condition in the area, and reusing water from the home in the garden.
The permaculture gardener is also looking to slow the rate at which water moves off the site. The best place for water to be stored is in the ground, where it is available for plants and microorganisms to use, so it makes sense to try and keep water on the plot as long as possible to allow it to soak into the soil. There are various ways of doing this, such as planting slopes with trees and cover crops to increase percolation rates, and minimizing areas of paving or similar hard surfaces that increase water runoff. Another technique available to the permaculture gardener in this endeavor is the construction of swales.
A swale is essentially a small ditch located on a slope that captures water as it runs down the slope and stores it, allowing the moisture to penetrate into the soil, infiltrating the soil profile around the swale and recharging groundwater supplies. This also has the added benefit of reducing erosion of the topsoil on the slope, and potentially providing a water body that can be utilized for irrigation elsewhere on the site.
Swales are built along the contour lines of a slope. This uses the natural topography of the slope to the advantage of capturing the water and also makes it easier to create a level swale. There are several ways to mark out the contour line along which your swale will go. You can use a laser level, a water level or a simple A-frame. This device consists of three pieces of wood – two of equal length forming the legs and a third braced between them – with a plumb line hanging from the apex. ‘Walk’ the A frame across the slope, adjusting at each step until the line is dead straight, and mark the ground. These marks will provide the line of the uphill edge of your swale.
If you have a steep slope that experiences a lot of runoff, you may need more than one swale. As a general rule, the steeper the slope the closer together and deeper your swales need to be.
Consider what will happen if your swale overflows. This could cause significant problems on land further down the slope. It is a good idea to include a spillway channel in your swale that will divert overflow to a ‘safe’ area. This could be to another swale further down the slope (indeed, some permaculture plots have a series of swales down a slope with each feeding into the next one downhill from it – in this instance it is a good idea to stagger the swales across the slope rather than having them all in a straight line down the hill), to another water body that has the capacity to hold the excess, or to an area of ground that requires a lot of water and will absorb the runoff.
Dig the swale along the contour line you have marked. The width and depth will depend upon the unique conditions of your site and the analysis you have done of it, but you will be likely be digging a minimum of 1.5 feet down. (It can be a good idea to dig your swale to your estimated required depth then wait until a major rain event and observe the action of the swale. If it overflowed quickly, you can go back and make it deeper before the next rains come.) Digging by hand will take a lot of time, so you may want to consider sourcing a mechanical digger, particularly if you are getting close to the season when rain runoff is most likely to affect your site. Use a water level or your A-frame to make the base of the swale level, but do not tramp it down; leave cracks within it to aid moisture infiltration. And as you dig the swale, pile the excavated soil on the downhill side of the swale. This will create what is called a berm, which helps stabilize the swale and provides planting opportunities.
Planting on the berm is a very effective way to help stabilize the soil around the swale. Use a variety of different plants, with different rooting strategies in order to stabilize all levels of the soil. Typically, a tree (usually fruit) will form the centerpiece on the top of the mound. Choosing a fast-growing variety will aid the stabilization effect. Utilize deep-rooted perennials alongside, as well as herbs and leguminous ground cover crops to stabilize the topsoil. Many of them will also absorb water from the swale, helping to prevent overflow. By planting in this way, you are effectively instituting a guild. The variety of root depths means that plants are not competing for water and nutrients in the soil, legumes add nitrogen to the soil to help all the plants in the guild grow, the tree provides shade as well as support, and, of course, you will be able to harvest crops from the guild. An example of a guild on a swale berm would be a pear tree surrounded by asparagus, strawberries and rhubarb (which all have roots at different levels in the soil profile), as well as dandelion, comfrey, chickweed and thyme as shallow-rooting cover crops.
Mulch the base of your swale. You could use pruned branches, straw or any other mulching material. This will help slow evaporation of moisture from the swale when it is full. Mulch the berm as well to prevent erosion, supply your plants with nutrients and keep weed species in check.
A permaculture swale is a technique that captures water in the landscape for passive irrigation and for slowing runoff. Learn what a permaculture swale is and why you might need one in your yard. Oh, and don’t forget to grab your FREE DOWNLOAD: How to Build a Swale to Capture Roof Water Quick Start Guide at the end of the article.
This article may contain affiliate links. Please read my disclosure for more info.
Irrigation for gardens and farms has always been a complicated subject. That’s because the possible solutions are as varied as the conditions on each property.
In permaculture design, we seek to solve problems in the landscape by working with nature and using techniques that are appropriate for the site.
For many gardeners and farmers, catching rainwater in the landscape can be a low-maintenance way to irrigate and improve soil quality at the same time.
When I started creating pockets of gardens and edible landscaping around my house, I wondered how I would find the time to hand-water all of those areas. And that’s when my love affair with the swale began!
What is a Permaculture Swale?
A permaculture swale is a shallow trench dug along the land’s contour, with a berm on the downhill side created with soil from the trench. All points along a contour line are exactly the same height above sea level.
Therefore, a trench along the contour captures water in the landscape, slowing and spreading it across the contour line. This action reduces erosion and retains water where it is needed.
Map showing contour lines with swale indicators. Image courtesy of www.midwestpermaculture.com
The above picture shows contour lines in pink. These indicate that all points along a single pink line are the same height above sea level. The hillside slopes downward toward the bottom right corner of the image, perpendicular to the contour lines.
Potential swale trenches are drawn in blue, while the planted berms below them are green. Without swales, the water on this hillside would rush down and form gullies, taking precious topsoil and nutrients with it.
Permaculture swales can ease the effort of food production while improving the local ecology. Each swale has unique characteristics to match the site’s conditions. In fact, the above picture is showing large swales on a large farm field.
Lucky for us that swales are also applicable at a residential scale. See how we constructed a swale in our front yard landscape!
>>> Learn more about permaculture.
You also don’t need a hillside for a swale to be useful! A gentle slope or flat land can also benefit from a swale.
Water management is the foundation of a low maintenance landscape.
Learn more about permaculture-based solutions in my award-winning book, The Suburban Micro-Farm.
Is a Permaculture Swale Right For You?
If this all sounds too good to be true, well, you might be right! Unfortunately, swales aren’t appropriate in all situations. They are great for gently sloping land, but not steep slopes. Also, on-contour swales might hold too much water in super rainy climates.
Keyline design and check-log terraces are a couple of strategies that have been used in these situations, and are worth exploring.
Keep reading to find out if a permaculture swale is right for you.
>>> Get more nitty-gritty details in my article How to Construct a Permaculture Swale.
Why a Permaculture Swale Could Be Helpful in Your Yard
- Mitigate stormwater runoff.
- Are an easier way to catch rain than using a tank or barrel.
- Are more efficient than tanks or barrels.
- Build self-sustaining ecosystems.
Let’s elaborate on each of those points.
1. A permaculture swale mitigates stormwater runoff.
Stormwater runoff is now the largest source of water pollution and is a huge problem in most cities. That’s because municipalities view water as a liability, so they send it away as fast as possible. With the existing infrastructure in cities, they’re right to be concerned about flooding.
However, sending water away as quickly as possible has resulted in horrible breaches of environmental stewardship. In my city alone, we send 13 million gallons of raw sewage into local waterways each year because the overtaxed sewer system combines stormwater with sewage during heavy rains.
How combined sewer overflow works. Image courtesy of www.CivicGardenCenter.org
We typically think stormwater is a problem that only governments, institutions, and experts can solve. In reality, there would be no problem at all if citizens did their part.
Though the problems of the world are increasingly complex, the solutions remain embarrassingly simple.” – Bill Mollison, father of permaculture, and author of Introduction to Permaculture and Permaculture: A Designers’ Manual
Here’s an example of how I did my part to help with the stormwater problem:
Our 1200 square-foot house catches 30,525 gallons of rain from the roof each year. How much water does your roof collect? We capture 75% of that, or almost 22,900 gallons in our landscape.
What if we all caught tens of thousands of gallons of water in the landscape, where appropriate?
Me thinks that the millions of dollars of taxpayer money currently going to fixing the sewer problem wouldn’t be necessary. Quick everyone! Dig a free swale! 😉 It also means that aquifers would be recharged and watersheds would remain healthy and intact.
2. A permaculture swale is a more passive solution for catching rain than using a tank or barrel.
Catching rainwater in tanks or barrels takes a certain amount of engineering skill. You have to:
- Buy a bunch of parts.
- Connect the downspout to the tank.
- Link multiple tanks together.
- Route the overflow either back to the sewer or run the overflow into the landscape.
- Add mosquito dunks regularly and clean out the barrel at least yearly.
- Install a spigot for filling up a watering can or connecting a hose.
All of these parts eventually degrade with sun and weather and need to be fixed or replaced over time. What’s more, there is very little water pressure from rain barrels, so using the water is quite frankly a pain in the ass.
Believe me, watering by hand takes a REALLY long time without water pressure. The solar pump I tried didn’t work very well. I think the inventors know that because it isn’t on the market anymore. 😛
Look at all of that engineering and purchasing of parts for a water source that ADDS maintenance time! Catching water in the ground using a swale can be so much easier. It allows you to passively water the garden with little work after it’s all set up.
Now, if you have rain barrels, don’t worry. I have rain barrels, too! Check out how I planned the overflow and made our rain barrels as super low-maintenance as possible. Don’t let thousands of gallons of water go to waste!
If you’re going to capture water for irrigation, whether in the ground or in a container, be a good neighbor. Plan it out properly so that you don’t flood your neighbor’s basement!
3. A permaculture swale is more efficient than tanks.
Good soil is thirsty. Organic matter acts like a sponge, easily holding several times its weight in water. Toby Hemenway in Gaia’s Garden tells us that three quarts of dry soil can easily hold one quart of water.
When we translate that to the soil in our yard, if our yards were covered in one foot deep of rich, moist soil, it would hold as much water as a 3-inch-deep lake the size of the yard. It would be cost-prohibitive to install a container that could catch that much water.
But the soil will hold it for free!
The berm of our front yard swale is densely planted with strawberries and flowers.
An urban neighborhood works with local permaculture practitioners to construct a swale and build a community food forest.
4. A permaculture swale builds a self-sustaining ecosystem.
An underground reservoir in a swale system.
Swales catch water and direct it to where it’s needed, which is in the soil. Instead of water running off or pooling above ground, swales direct it downward into an underground reservoir.
Nature has its own built-in, self-watering system. When water is needed, it is naturally released. No work on our part after the swale is built!
This underground reservoir attracts microorganisms. Suddenly the soil is alive, and voila—we’re generating organic matter and fertilizer right in the place where we need it.
This means fewer inputs, which saves money and time. The more the organic matter builds, the more moisture it holds. With more organic matter, the system can better withstand both floods and droughts.
As the water reservoir and nutrients in the soil build, gardening will become a breeze for you.
Water management is the foundation of a low maintenance landscape.
Ready to construct a permaculture swale in your own yard?
See my article how to construct a swale in the residential landscape or check out my free download:
Need more ideas for growing a permaculture garden?
- Create a Permaculture Food Forest
- How to Build a Fruit Tree Guild
- 6 Maps to Draw for the Permaculture Farm Design
Have you built a permaculture swale on your property? What benefits have you noticed?
- Delivering SuDS
- Using SuDS
- Sustainable drainage
- Urban drainage
- SuDS principles
- SuDS principles
- Early engagement
- Using surface water as a resource
- Source control
- Managing water on the surface
- SuDS management train
- Pollution prevention
- Benefits of SuDS
- Benefits of SuDS
- Why developers should choose SuDS
- Flood risk management
- Water quality management
- Biodiversity & ecology
- Air quality
- Building temperature
- Carbon reduction and sequestration
- Economic growth
- Enabling development
- Flexible infrastructure/climate change adaptation
- Groundwater recharge
- Health and well being
- Pumping wastewater
- Rainwater harvesting
- Traffic calming
- Treating wastewater
- SuDS components
- SuDS components overview
- Source control
- Source control overview
- Green roofs
- Rainwater harvesting
- Pervious surfaces
- Pervious surfaces overview
- Benefits of pervious surfaces
- Hydraulic performance
- Hydraulic design criteria
- Hydraulic design criteria
- Maintenance of pervious surfaces
- Specification of aggregates
- Pervious surface types
- Pervious surface types overview
- Water quality performance
- Structural Performance
- Construction options
- Permeable surfacing options
- Porous surfacing options
- Other permeable surfaces
- Swales & conveyance channels
- Swales & conveyance channels overview
- Channels and rills
- Filtration overview
- Bioretention areas
- Filter trench
- Filter strips
- Infiltration overview
- Rain gardens
- Infiltration basin
- Infiltration trench
- Retention & detention
- Retention & detention overview
- Detention basins
- Retention ponds
- Geocellular storage systems
- Wetlands overview
- Inlets, outlets and control structures
- Inlets, outlets & control structures overview
- Inlets, outlets and controls
- Vortex control systems
- SuDS performance & monitoring
- SuDS performance and monitoring
- Flood risk management benefits
- Water quality benefits
- Biodiversity benefits
- Amenity benefits
- Multiple benefits
- Design selection
- The costs & benefits of SuDS
- Comparison of costs and benefits
- Guidance on cost benefit analysis
- Adoption & maintenance of SuDS
- SuDS adoption in England and Wales
- SuDS adoption in Scotland
- Legislation & regulation
- England and Wales
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- National Standards for Sustainable Drainage
- Design guidance
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- Retrofitting SuDS
- Why retrofit?
- Why change?
- Realising the benefits
- Enabling retrofitting
- Identifying opportunities
- Opportunistic retrofitting
- Strategic retrofitting
- Retrofitting in the urban environment
- Combining urban design & SuDS
- Key objectives
- Realising opportunities
- A framework for retrofitting
- Why retrofit?
- Drainage exceedance
- Drainage stakeholders
- Floods in urban areas
- New developments
- Drainage design & standards
- Managing exceedance
- Managing exceedance
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- Building layout
- Downstream impacts
- Encouraging uptake
- Background & outputs
- Key learning points
- Case studies
Swales & Berms vs Concrete: Low Tech Solutions for Stormwater Runoff
Here’s a sample of email questions I’ve been getting lately:
- What can I do with all this rainwater? I have rain barrels, but they overflow. How can I deal with the overflow?
- I don’t have time or money to install rain barrels or gutters, but I still would like to save rain water, what can I do?
Swales or berms could be your answer. They are literally as old as the hills and have been used to control water flow for centuries. Today they are still used around the world but have been all but forgotten here in the United States as a way to conserve water. (This is getting to be a familiar refrain!)
What’s a Swale?
Swales are simply shallow, low depressions in the ground designed to encourage the accumulation of rain during storms and hold it for a few hours or days to let it infiltrate into the soil. Swales ideally are tree-lined and store water for the immediate landscape as well as help cleanse the water as it percolates down. Swales can be installed separately or as part of a larger water rain catchment system with rain gardens, cisterns and other water conservation measures.
Swales are one of the cheapest and easiest water storage methods and can be installed almost anywhere. If properly built they greatly reduce storm runoff; thereby reducing the impact of storms on local storm runoff systems. But more importantly they catch and preserve fresh rain where it can be used by your shrubs and trees. Swales are an easy solution that can be effective in homes, commercial buildings and along street mediums in place of curbs.
What’s a Berm?
Berms are raised beds that can be used to direct water to swales. They are the equivalent of the slope in road used to push water off the middle of the road toward the curbs.
Ideally, berms and swales should be designed into the landscape where there is any noticeable slope to slow and capture runoff. They can be part of the site plan for an individual home or integrated into the design of an entire multi-unit complex or subdivision development.
Research Reveals Ancient Truths: Real Benefits
Recent research in Spokane, Washington, as well as Florida has documented the storm water quality benefits from swales and low-lying areas by reducing the flow and allowing slower infiltration into the groundwater system.
This is a finding which past generations were aware of. In our hurry to pave the world wit concrete, we threw our knowledge of swales and berms out with the stormwater (how’s that for a mixed metaphor?).
It is best when designing the home landscape to preserve low-lying areas such as wetlands and swales. These low-lying areas retain storm water, provide water quality filtration and may allow for some infiltration to replenish groundwater supplies.
Swales can either be grassed, gravel or rocked. All designed to slow and retain the flow of runoff. They can also be used instead of costly curbs and gutters found in most neighborhoods and communities today.
As an example, at Prairie Crossing, a 678-acre residential development 40 miles northwest of Chicago in Grayslake, Ill. adopted conservation designs to reduce runoff rates and volumes and to reduce pollutant loads.
Storm water is routed into swales, rather than storm sewers. The swales provide initial storm water treatment, primarily infiltration and control sedimentation. The prairies diffuse the water and soils retain contaminants, slowing storm water velocity.
The development expects about 60 percent of the land to be devoted to open spaces. Residents also employ rain gardens and expect to retain 65 percent of its storm water onsite and reduce nutrient loads and reduce heavy metal pollutants by 85 to 100 percent.
Maintenance costs for storm water controls are expected to drop, downstream conditions have improved and there’s less flooding. A sign of success has been thriving populations of native fish in the 22-acre lake.
Key elements to consider when building a swale include:
- Swales are not intended to move water but to hold water for soil absorption.
- The width of the swale should be covered by the crown of the mature surrounding trees.
- Soil in the swale should not be compacted or sealed but should be loose to encourage absorption.
Surprisingly one tree can reduce stormwater runoff by 4,000 gallons a year thus greatly reducing the need to build costly water treatment plants. So swales lined with native trees are an extremely-cost effective, and often overlooked low-tech, water conservation technique.
Swales with the proper plants and trees help manage runoff and make water healthy for people, nature and fish.
Swales are a low-cost win-win solution. Isn’t it time we tried them?
- Related Article: Passive versus Active Harvesting
- Related Article: Conserve Water by Mimicking Mother Nature
- Related Book: Rainwater Harvesting for Drylands (Vol. 1): Guiding Principles to Welcome Rain into Your Life And Landscape by Brad Lancaster
- Related Book: ASwale Guide: Permaculture: A Practical Guide for a Sustainable Future by Bill Mollison
Truly wonderful books!
How to Build a Bio-Swale (and Why You Should Want To!)
Unlike a typical drainage ditch, a bio-swale is perfectly level, meaning water that flows into it from uphill doesn’t flow in one direction or another – instead, a bio-swale fills up like a bathtub during a big rainstorm; afterward, the water slowly seeps into the soil where it is available for crops planted nearby. There are two parts to a bio-swale: the swale, which is an excavated area where water can collect, and the berm, a raised mound on the downhill side of the swale made from the excavated soil. While drainage ditches tend to be skinny with steeps sides, both the swale portion and the berm of a bio-swale are broad and gently sloping, making them quite attractive and useful for planting. Because bio-swales must be perfectly level, they resemble topographic lines, often giving them an attractive undulating shape across a slope (the rice paddies of Indonesia and terraced vineyards of Italy are based on the same concept)
Bio-swales arrest the process of erosion by slowing water down when it pours across a slope. Any soil that has been carried off from uphill is deposited in the bottom of the bio-swale and moisture is concentrated around it, making for a lush, fertile planting location. Besides reducing erosion, recharging groundwater and building soil, bio-swales can also be part of your manure management strategy. One of the best places to build a bio-swale is at the bottom of a pasture or a chicken run where they will soak up manure-laden runoff and concentrate it in a location where you can plant a crop to make use of the nutrients – rather than letting the nutrients wash downslope into the nearest waterway, where they would become a pollutant.
Fruit trees, berry bushes, and other perennial crops are the best choices for planting around a bio-swale; they are not a landform that can easily be tilled and planted with annual crops. Some growers build a bio-swales every 10 or 20 feet down a slope and use them as planting strips for an orchard or vineyard. On small properties, a single bio-swale at the bottom of the garden makes a convenient place to plant a border of fruit trees and perennial herbs and flowers, while soaking up runoff before it flows off the homestead.
Fall is a sensible time of year to build a bio-swale, because the weather is cool and the soil is usually soft and moist. A lot of digging is required, so you may want to organize a bio-swale party to lighten the labor.
Step One: Mark It
Ditches are designed to carry water away, which means they are sloped downhill. Swales, however, follow the contour of a hill, so the water that drains into them doesn’t flow one way or another, but fills the swale when it rains. This means the bottom of a swale needs to be level (i.e. have the same elevation from one side of the swale to the other). So, the first step is to mark the ends of the swale across the slope.
- Place a 4-foot carpenter’s level on the ground at one end of the area where you want the swale to be located, and adjust it until it reads level (meaning you’ve found ground that’s perfectly level horizontally). Pound a wooden stake into the ground at both ends of the level to mark the location.
- Slide the level laterally across the slope in the direction where you want the swale to go, and put one end against the stake that was just pounded in. Adjust the other end of the level until the it reads level. Pound in another stake.
- Repeat this process across the slope until you’ve reached the end of where you want the swale.
Hint: Remove any debris that is on the ground under the level to get an accurate reading.
Step Two: Dig It
The line of stakes shows you where to start digging.
- Excavate a broad shallow basin in the area immediately below the line of stakes and pile the soil on the downhill side of the basin to form a broad, gently sloping berm. There are no hard rules about the size of a swale, but the bigger it is the more water it can absorb during a rainstorm. Six- to 12-inches deep and 3- to 4-feet wide are typical dimensions.
- Smooth out the shape of the berm with a hard metal rake to form a planting bed. The slope of neither the berm nor the swale basin should exceed a 1:3 ratio to ensure the stability of the bio-swale. (In other words, don’t let the slope drop more than 4 inches for every 12 inches of length).
- Remove the stakes.
Hint: Stand on the uphill side when you’re digging to make it easier.
Step Three: Plant It
The bottom of the swale basin is only suitable for plants that thrive on high moisture levels, such as wetland species like reed and sedges. However, clover, most grasses, comfrey, and numerous other plants will tolerate the occasional inundation that occurs at the bottom of a swale.
The berm is the best place to plant fruit trees, berry bushes, vine, herbs, flowers, and anything else that likes loose, rich soil, but requires excellent drainage. Over time the swale basin will fill in with loose soil and organic matter, creating a rich reserve of nutrients for the roots of the plants to tap into.
A swale is quite simply a ditch & downhill mound (also known as a berm) dug on a contour. It can be anything from 5 feet to 5 kilometres long. Swales collect water during and after rainfall, allowing for a slow and consistent drainage of water into an area.
Over time this collects silt and surface nutrients, creating a moist, fertile location for growing trees and other plants.
Swales can be used to channel water run-off from roads, yards and car parks or they can be used to move water through a site.
Swales can follow contour or have an incline up to 6 degrees depending local conditions. The easiest way to establish a contour line in your orchard or pastures is to use a rotary laser level – these are expensive to purchase but can be hired out easily enough. For a comprehensive how-to, see Rotary Laser Level How-to
For other contouring methods, see Simple surveying techniques
There are a few things to keep in mind when installing a swale
- During very heavy rainfall, swales can overflow. If flash floods are a possibility, and to avoid erosion – you should include a rock-lined spillway to a lower swale, drainage ditch or catchment dam.
- Pools of water in the swales may result in mosquitos in warmer climates, it is recommended to mulch in the swale to reduce standing water. Also, planting of water loving ground covers help to stabilise the soil and absorb excess water
- Swales can be adapted to almost any environment but may not be appropriate for areas with a high water table or on extremely steep slopes.
- Swales are most suited for deep rooted perennial plant species, trees, bushes & nitrogen fixing ground covers where regular access for maintenance or harvesting is not required
Common species to plant on swales
- Fruit & nut trees
- Windbreak trees
- Berry bushes (gooseberry, gojiberry, blackberry, etc)
- Peas, beans, peanuts
- Root vegetables – sweet potatoes are especially productive in swale conditions
Swales, Berms & Mycelium – Edgewood Gardens’ Permaculture Paradise!
Edgewood Gardens in Jacksonville, USA, have had a makeover – becoming a permaculture paradise.
Through a variety of methods, this project shows how well permaculture design works to create an abundant, balanced and natural system.
The land was originally pasture, with water running across the field off onto a nearby road and then down a drain.
By building swales, water is captured, remaining on site to irrigate the berms, where the fruit trees, shrubs and vegetables grow.
Using mycelium in a wood chip mulch also helps retain moisture, whilst working in a symbiotic relationship with plants, swapping nutrients for plant sugars.
The three-sisters growing method of corn, beans and squash, utilises space, and again works as a symbiotic relationship between each plant.
Planting herbs and flowers attracts pollinators for the plants and fruit trees plus creates a pest control system so that pesticides are not needed.
A variety of fruit trees have been planted, a mulberry because its speed in growth creates quick shading and a loquat, which is easy to grow from seed, is hardy and fruits in January when fruit is at a minimum.
Native plants are used as much as possible, providing a garden suited to its environment.
A great example of design and mulit-stacking functions.
Aranya explains: What is permaculture – part 3: design
Editor Maddy Harland explains permaculture design in her series: Permaculture Principles
Permaculture Design – a step-by-step guide by Aranya for a special price of £11.20
Watch: Inhabit – permaculture explained
Permaculture – practical solutions for self-reliance, a magazine filled with useful and inspiring features, stories and ideas about all aspects of sustainable living from gardening and farming to green building and renewable technology. Check out a free digital copy HERE. You can subscribe to the print edition HERE.
Swales are amongst my favorite permaculture projects. Though they can be laborious, especially for a shovel and pick fellow like me, they show results quickly and look amazing, texturing the landscape with both purpose and beauty. They are easy to explain: Everyone understands the concept of plants needing water. Swales are also perfect for those of us wanting to build no-dig garden beds, as digging the (swale) paths provides the necessary topsoil.
There are so many more reasons. Modern inclination is to get rid of rainwater as quickly as possible, ushering it into gutters and drainage systems, which often lead to a plethora of contaminants, including sewage getting into fresh water sources. Afterwards, when there’s a dry spell for a few days, the sprinklers come out. Instead, swales stop the deluge and allow the water to slowly, passively enter the soil and keep stuff working, preventing overfilling drainage systems and the need for compulsive watering. What a concept!
So, with such an endorsement, surely everyone is salivating at having a swale of their very own, even those who still aren’t quite certain what a swale is. Well, if that’s the case, hang on for another paragraph or few, and let’s get to it.
The Swale on Contour
For the sake of swale newbies, the basic concept of a swale on contour is to catch water as it drains and hold it in place until it absorbs into the ground. It looks a bit like a massive ditch with closed ends, trapping all of the water as opposed to having it flow anywhere. Other swales systems, also known as diversion ditches or soil conservation swales, are meant slow down the movement of water in order to allow it to partially absorb, catch sediment, and/or prevent erosion while slowly ushering it elsewhere, like a reservoir. However, a swale on contour aims to keep all the water in place until it is absorbed.
“On contour” simply refers to the fact that this sort of swale works on the principle that by keeping everything level, such that the path of the swale moves along the contour, or elevation curve, of a slope. Doing this means that the water absorbs evenly into the land below as opposed to flowing to the lower end of the swale. Without following the same elevation level, the water would flow to one side or the other, and preventing this flow is what makes the water become passive rather than destructive, as is the case with water draining en masse and quickly in one direction.
Lastly, another nearly ubiquitous feature of swales is the result of all the soil that is removed to create them: the berm. The berm sits on the downhill side of the swale and is the perfect place to grow trees and deep rooting plants like strawberries, rhubarb, asparagus, comfrey, and dandelions. The deep roots will keep the berm stable, as well as suck up the moisture from below so that the newly hydrated soil doesn’t become overly saturated.
The Right Tools for the Job
In a world with greater money sources than spring from my pockets, as well as more technological knowledge than I currently retain, swales can be fairly hi-tech operations. Laser levels can help find the contour lines of a property, and major league digging equipment can be brought in to quickly, painlessly (at least from the human side of things) excavate. For a massive swale, something more river-like than what most of us will attempt, this makes sense. For me, however, the world of swales is a bit more rudimentary.
To be completely frank, half of the reason I got into gardening and, subsequently, permaculture is that I enjoy being outside and on a project, getting dirty and fixing problems. If there’s a hole (or swale) to be dug, I want a shovel. If there’s something that needs to be level, like the bottom of a contour swale, well then, a water level will suit me just fine. And, when it comes to finding that contour line, I was both happy and enlightened to discover the simple but effective A-frame.
An A-frame is called thusly because basically one must build a capital “A” out of wood to make it. The two legs need to be of equal length, just as our elementary school teachers taught us, and about midway down, they’ll be connected by a third piece of wood, equidistant from the bottoms of the legs. Aim for the open end of the A to be between three and six feet. Then, there are two options:
1. Mark the exact center of the crosspiece and hang a plumb line from the center point at the top of the A. When the plumb line hits that centerline on the crosspiece, then the two feet of the A are on level playing fields.
2. Or, simply strap a water level to the cross bar so that when it’s level the two pieces of ground upon which the A is resting are the same elevation.
Choosing the Right Place
Before digging anything, it’s important to carefully determine the rough location of where to place a swale. In doing so, it’s imperative to consider the gradient, as a swale should only put installed on something with nothing more than 15% gradient, or a slope that climbs roughly 1 meter for every 7 meters it moves horizontally. Following this rule prevents mudslide problems that steeper gradients would cause, and that could potential be devastating to a property.
Other things to consider are that the longer the swale can stretch the wider reaching the water absorption will be, and the higher it’s placement the more space in which the water will have to expand underground. So, ideally, a swale will be installed at the highest point possible but still low enough, downslope, to catch water run-off. From here, spread the water out on level plain by extending the swale on contour for as long as possible, that way water can absorb evenly into the land downhill.
Lastly, what I’ve noticed in my successes and failures of playing with swale systems is that, if there isn’t a noticeable flow of water to feed the swale, it may not fill, rendering the effort much less advantageous than once hoped. I’ve built several swales, some of them absolutely required a passive overflow, others never held more than a couple of inches of water in the middle of a rainstorm. I now make sure I know where a significant source of water will be coming from before putting in the effort.
Putting the Right Tools to Use in the Right Place
Once the general area is decided upon, it’s time to get more specific, which means pulling out that A-level we built a couple of sections ago. Use the A-level to stake out the contour line and the exact route the swale will be taking. This will likely not be a straight line, but rather a sexy, curvy number that’ll give the system some personality, like those amazing terrace gardens in Asia. Mark the entire thing out, including a safe area for water to passively overflow should the swale fill up completely.
Using the marked contour line, dig vertically into the hill, piling the dirt on the downhill side of the swale. The depth of the swale should remain the same and can be measured from the established contour line then leveled with a water level or the A-frame later. The general idea behind digging the swale is that it should be about three-times as wide as it is deep, and the berm—the pile of excavated dirt—should be mounded to create the upper part of the bottom side of the swale. Make sure that the base of the swale is level so that the water disperses evenly.
Other than catching and storing water on your land, the biggest benefit to having a swale is the growing potential of the berm. It will be mostly composed of rich topsoil that’ll be well hydrated. It’s important to plant on the berm immediately to prevent it from eroding. Trees will help to make sure the soil doesn’t get too saturated. Deep rooting plants—the aforementioned strawberries, rhubarb, comfrey and so on—will help to stabilize it. And, as always, a good, nitrogen-fixing ground cover is going to stop the earth from drying out or getting overly weedy while simultaneously enriching the soil.
The Finishing Touches
Another important aspect of making a swale and, particularly, avoiding possible problems is to plan for passive overflow. The best way to do this is to have a sizeable, say equally as wide as the swale is, spot that is perfectly level and below the top of the berm where water can overflow into a safe place, either a pasture or another swale or a water catchment like a pond or damn. At the overflow point, it’s best to have something like a plastic sheet, stones or—ugh!—concrete to prevent erosion.
Once the base of the swale is satisfactorily level, a nice thick layer of mulch is a good idea. It will add nutrients to the water that is going into the soil below, as well as prevent evaporation. In fact, many people choose to fill up their swales in order to make convenient and logical access paths around the property. It’s just another viable purpose for having a swale.
After that, it’s just the permaculture way: Observe, find solutions within the problems that arise (with the right steps these shouldn’t be too grand), and reap the productive benefits of forethought and working with nature.
Swale Landscaping Benefits
Does your property have excessive runoff from rainwater or melting snow? All that liquid can not only make your yard a soupy mess, it can even threaten the structural stability of your home. Digging a swale in your yard will reduce or eliminate this serious problem. A swale will also help conserve water and create a lovely, low maintenance landscape for your home.
What is a swale and why build one on your property?
The landscaping term “swale” refers to a shallow trench, which may be dug on a property for 3 important related purposes:
- to catch storm water
- to direct the water away from your home
- to slow the water’s movement so it can be gradually absorbed into the ground
A swale usually is designed to follow the natural contours of the surrounding landscape, often with a berm (a human-made ridge of earth, which may be sown with plantings for stability) along the lower edge.
A driveway swale flanks your drive on one or both sides, in order to keep runoff from flowing into your garage or your home.
A swale may be combined with underground piping to handle your roof runoff.
The standard swale dimensions generally range from 6-18 inches deep and 8-24 inches wide, depending on the volume of water you are dealing with.
The many benefits of swale landscaping
Digging a swale will benefit your landscape in a number of ways. You will
- Avoid storm water pooling around your house and prevent damage to the foundation.
- Help hold off flooding of your house, garage, and yard – and perhaps your neighbor’s property.
- Reduce soil erosion and loss of high quality top soil.
- Collect rainwater much more easily than with a barrel or tank system.
- “Recycle” rainwater to irrigate your garden, for a flourishing low maintenance landscape.
Before you start to dig a swale
Contact a one-call center for clearance before you begin swale construction, or any other home improvement that involves digging. Otherwise, you run the risk of hitting underground utility pipes or cables … and the hefty fine that can result.
In addition, check with the building authority in your area to see whether you’ll need a permit for the job. Many local governments have enacted strict laws concerning landscaping work that could possibly affect the groundwater system.
Consult a professional landscape contractor to plan and implement your project in the best way.
A swale as part of your landscape design
Plan your landscape design to include your swale. Make sure that any new feature you install, such as a fence, will not block the flow of runoff through the swale.
The swale does not need to be an unappealing stretch of bare earth. You can seed it with grass, but be sure that your swale’s sloping sides won’t make it too difficult to mow your new patch of lawn. An alternative is to plant it with low care wetland species such as cattails or lovely marsh hibiscus.
You might prefer to line the swale with nice-looking pea gravel or river rocks. Besides permitting storm water to infiltrate the soil more efficiently, small stones will give your swale the attractive appearance of a dry creek bed.
Finally, permeable pavers are perfect for stabilizing the bottom of a swale which will double as a garden walkway during the dry season.
Laura Firszt writes for networx.com.