Rescue Earth System

Infiltration Swales

A Global Water Infiltration, Flood Control, Nutrient Loss Reduction and Bioremediation Strategy that seamlessly incorporates Nature Belts / Wildlife Corridors into a diverse range of settings.

Infiltration Swale Systems

Nature Belts, Water Infiltration & Flood Control Measures

Swales come in many forms, they have many names, and they have many functions! They are an ancient water infiltration technique that is thousands of years old. Permaculture Swales are a good example of forested swales. We have named ‘our’ version as — Infiltration Swales — as this is the primary function that we want most of our swales to perform. They will be designed to also function as Nature Belts / Wildlife Corridors and as a Flood Control Measures in both urban and farming areas.

We propose that millions of kilometres of existing agricultural drainage contours can be repurposed to function as Infiltration Swales and as diverse species Nature Belts & Wildlife Corridors. Furthermore, where needed,  numerous cost effective Bioremediation functions can be added. Nature Belts and prairie strips are a trend that is already happening throughout the world, even in big Agriculture.

We need to focus a great deal of our efforts on the urban and farming areas that are rapidly expanding into natural areas. Population growth and the degradation of farmed landscapes is forcing people to find new land. We need to reverse this trend by repairing damaged farmland and reduce population pressures by maximising urban food production and reducing population growth.

By strategically placing strips of prairie plants in-between row crop or along streams and waterbodies, farmers can reap a multitude of benefits. Prairie strips can aid in reducing erosion and nutrient runoff, increasing habitat and food sources for wildlife, and stream bank stabilization

What is an Infiltration Swale?

Infiltration Swales are broad, shallow, linear, vegetated on-contour channels with gently sloping sides which temporarily hold surface water so that it infiltrates into the soil. Water in excess of swale capacity is passively discharged into a Constructed Wetland, Rain Garden LID System or a waterway.

The drawing above is a good example of a general purpose on-contour swale. Anyone who has put in drainage contours in agricultural land will recognise this shape!

Where can Infiltration Swales be Used?

Infiltration Swales can be used just about anywhere on gently sloping ground. Although the primary purpose of ‘our’ Infiltration Swales is rehydrating landscapes, they have many functions especially when integrated with other regenerative practices. Below are four ways the Rescue Earth System will be using swales.

Urban Areas

In urban areas, Infiltration Swales serve the purpose of slowing down stormwater run-off and infiltrating much of the water in order to reduce peak flow and thus reduce the risk of localised flooding. Infiltration Swales also reduce reduce the risk of flooding downstream by minimising the flow rate and volume of water that enters the conventional urban drainage system before it reaches the water basin.

Agricultural Land

On agricultural land, Infiltration Swale Systems are paired with Nature Belts & Wildlife Corridors or Diverse Cover Crops. Nature Belts & Wildlife Corridors and the Bird Habitat Restoration Initiative are part of the Regenerative Restoration Initiative.

When there is a need for bioremediation, Ag Bioswales are used instead of standard Infiltration Swales. Bioremediation refers to cost-effective and environment-friendly method for converting the toxic, recalcitrant pollutants into environmentally benign products through the action of various biological treatments.

Grazing Land

In grazing areas, Infiltration Swale Systems are paired with Keyline Ploughing and Regenerative Grazing Management. Although they have different ojectives, all three initiatives substantially improve water infiltration and groundwater recharge.

The inclusion of Leaky Check Dam Systems in erosion gullies, eroding waterways, streams and small rivers is an important intervention especially when they are paired with Ecosystem Restoration. Leaky Check Dam Systems are also a great way to create riparian habitat for wildlife and they are thus an integral intervention for Bird Habitat Restoration.

Keyline Ploughing and Infiltration Swales are often used together to rapidly increase the rehydration of the landscape.

Permaculture Systems

Permaculture styled Infiltration Swales are used in both urban and rural settings and are predominantly tree based systems.

Integrating Nature Belts & Wildlife Corridors


Nature Belts (prairie strips) are a conservation practice that protects soil and water while providing habitat for wildlife. Small portions of crop land are taken out of production and planted with native plants for conservation benefits for the entire field.

By planting 10% of a field into 5m to 10m strips of native plants along the contour, farmers can reduce soil movement by 95% and phosphorus loss by 90%. Total nitrogen in surface water is reduced by 91%. In-field native plant strips retain soil and nutrients on the field and have an added wildlife benefit.

The benefits of integrating Nature Belts & Wildlife Corridors with Infiltration Swales and the transition to Regenerative Farming Practices amplifies the above results to levels that are listed below:
  • 90% reduction in water runoff
  • 99.9% reduction in soil loss
  • 99.9% reduction in phosphorus runoff
  • 99.9% reduction in nitrate-nitrogen runoff
  • No difference in yields for wet years
  • Significant yield increase in drought years
  • No difference in weed abundance
  • Reduced emissions of heat-trapping gases, especially nitrous oxide
  • Improved beneficial insects and wildlife

The benefits for the environment go way beyond the list above!

Infiltration Swales and Saturated Buffers can feed clean water to a Wildlife Corridor as part of an Ecosystem Restoration project.

Urban Areas

In urban areas we intend to integrate Nature Belts & Wildlife Corridors with Infiltration Swales through the Public Places / Placemaking Initiative.

Using Ag Bioswales as Denitrifying Bioreactors

Nitrogen (N) and phosphorous (P) are the most important nutrients in fertilizers for agriculture. While some of them are taken up by plants or adsorbed to minerals or organic matter, a proportion of the nutrients can be leached from agricultural fields into rivers, lakes, and oceans, causing eutrophication. Agricultural runoff water is considered a major cause of the hypoxic zones, also known as the dead zones, in many of the worlds oceans.

Large amounts of nutrients are released from agricultural fields through subsurface perforated pipe (tile) drainage, which is installed to improve soil conditions for root growth, thereby increasing agricultural productivity, it has also increased the amount of nutrients, especially nitrate, released from fields into surrounding waterways. Low-cost and simple technologies are thus urgently needed to reduce watershed export of excess nitrogen and phosphorous to sensitive aquatic ecosystems.

A key role of wood chips in the Rescue Earth System is to help with bio-remediation. Although most of the Rescue Earth Infiltration Swale Systems may have some wood chips added, Ag Bioswales have a very deep layer mixed with other key bio-remediation ingredients such as CCHP Biochar, rock dust, etc. plus many other bioaugmentation and biostimulation ingredients.

Anyone that has made compost before knows that decomposing wood chips require a lot of Nitrogen. By filling the Ag Bioswale with tons of wood chips it becomes a denitrifying bioreactor. All excess water that drains from an agricultural land flows into the Ag Bioswale. Bacteria and fungi that feed on wood chips, consume the nitrates in the drainage water, and turn the wood chips into compost.

While the actual design of the Denitrifying Ag Bioswale is simple, the chemistry and biology that happens inside it is complex. Denitrifying Ag Bioswales can remove up to 100 percent of nitrates from the water flowing through them. This includes nitrate laden water from perforated drainage pipes. This is possible because the composting process requires so much nitrogen. Wood chip mulches are very common in the Regenerative Farming / Permaculture movements.

Although conventional denitrifying bioreactors (anaerobic bacteria) can typically operate for 10 years before wood chips need to be replaced, the highly biologically active composting process of our Denitrifying Ag Bioswales (aerobic & facultative bacteria plus fungi) produce a much needed fungally dominated compost within three years. The high quality compost can be spread on the land and the wood chips replaced with a fresh batch.

Wood chips are not the only source of organic carbon one can use, and other media can be used as Denitrifying Ag Bioswale fill. Other carbon sources include crop residues, cardboard, newspaper, etc. However, wood chips are the recommended fill material because they last longer and are generally more uniform than these other carbon sources.

N.B. Denitrifying Ag Bioswales are a solution to excess nitrates during the transition of Industrial Agriculture to Regenerative Agriculture, and they will transition to being Infiltration Swale Systems and continue working for hundreds of years.

Results from a decade of testing in IOWA, USA, show that converting just 10 percent of a crop field to prairie strips could help farmers reduce runoff of water by 44 percent, sediment by 95 percent, phosphorus by 90 percent and nitrogen by 84 percent. The areas tested were all on corn and soybean farms.

Using Ag Bioswales + Bioaugmentation + Biostimulation
to Degrade Industrial Ag Runoff Contaminants

In addition to the well known hypoxia causing agricultural nutrients mentioned above — Nitrogen (N) and phosphorous (P) — Industrial Agriculture has added many more dangerous chemical contaminants to runoff and drainage water, thereby degrading many sensitive aquatic ecosystems in streams, rivers, wetlands, lakes, oceans; and ultimately the quality of the water we drink!

A Global Nutrient Loss Reduction and Bioremediation Strategy is urgently needed to address the barrage of chemical contaminants from farmland that are adversely affecting our ecosystems, our food production, and ultimately our health — and reducing the fertility of our soils in the process. 

Although they are not a silver bullet, Ag Bioswales + Bioaugmentation + Biostimulation can be used to degrade contaminants by bio-remediating the runoff and drainage water, and to use up the excess nutrients in the process of the decomposition of incorporated wood chips, and in plant growth before contaminants can infiltrate into ground water or reach a waterway.

For Ag Bioswales + Bioaugmentation + Biostimulation we add much more diverse wood chips, CCHP Biochar, Rock Dust, specific nutrients and biostimulants, bacteria and fungi inoculants, etc. so that 99.9 % of the contaminants are degraded or incorporated into complex carbon compounds predominantly via mycoremediation pathways. Fungi play a major role in bioremediation owing to their robust morphology and diverse metabolic capacity. Though a lot of work is done in the area of mycoremediation, there are still some areas like degradation pathways which are not totally understood.

N.B. Ag Bioswales + Bioaugmentation + Biostimulation are a solution to excess contaminants during the transition of Industrial Agriculture to Regenerative Agriculture, and they will transition to being Infiltration Swale Systems and continue working for hundreds of years.

Stormwater management is a key intervention for habitat conservation / restoration projects.

Urban Bioremediation Swales (Bioswales)

Urban Bioremediation Swales are designed to infiltrate, store or convey surface water (reducing runoff rates and volumes) and remove pollutants through bio-remediation. They can also be used to passively convey storm water to Constructed Wetlands or to Rain Garden LID Systems which are designed to promote bio-remediation, infiltration and groundwater recharge.

Similar in function to our Bioremediation LID Systems, Urban Bioremediation Swales are applicable to a wide range of situations. They are typically located next to roads, where they replace conventional gullies and drainage pipe systems, but examples can also be seen of swales being located in landscaped areas, adjacent to car parks, alongside fields, and in other open spaces. 

Urban Bioremediation Swales are ideal for use as drainage systems on industrial sites because any pollution that occurs is visible and can be dealt with before it causes damage to the receiving watercourse. Dr John Todd’s work on bio-remediation systems on highly toxic industrial waste water is legendary.

The promotion of settling is enhanced by the use of dense vegetation, usually grass, which promotes low flow velocities to trap particulate pollutants. In addition, check dams or berms can be installed across the swale channel to promote settling and infiltration. As a result, swales are effective in improving water quality of runoff, by removing sediment and particulate pollutants. In wet swales, the effectiveness is further enhanced by providing permanent wetland conditions on the base of the swale.

The drawing above is of a typical Permaculture Food Forest Swale

Permaculture Styled Food Forest Swales

A swale is a long, shallow dug-out trench, running level along the contour of a slope, with an adjacent berm on the downhill side. The “berm” is a soft mound made of loosely piled, non-compacted soil which acts as a retaining wall. On contour means following the progressive decrease in the height of the land at regular, level intervals, which mark the boundary, outline, or shape of the land.

The purpose of a swale is to harvest water passively. Over time, this will establish a permanent growing system, storing moisture in the soil for long-term food and water security. They also help deal with storm water run-off, and reduce erosion by slowing down the flow of water.

As water flows downward, the berm interrupts and collects it in the level bottom. Water fills up the swale, the mound passively soaks it up, and forms an underground water lens of moist soil. This hydrates the soil and sub-soils below and boosts the effectiveness of horticulture and agroforestry. As the water percolates downward, it eventually hits the bedrock and moves horizontally, accumulating at the bottom of the lower slopes. Over time, this creates new springs, recharging aquifers and creating a natural water resource.

Swales can also be used to grow many varieties of plants, and are ideal for growing a wide range of crops on a single mound. Any trees planted on the swale will work in concert with the earthworks to open up the soil for more water and make the land drought proof. Over time, the trees will need no irrigation because they get it all from the soil.

Your swale might also serve as a windbreak, privacy fence, or a native habitat for animals. You can build them along footpaths, along Hugelkultur mounds, or connect them to other swale systems and ponds to create long-lasting water reservoirs. They can even be arranged to receive water from buildings, roads, downspouts or runoff areas. Some of these swales may feed into a drainpipe that connects with a pond. You can also set up the overflow from your pond to feed into a larger swale.

When creating a pond system, build it at the highest level of your property to create water pressure that can power your water systems. Store water in your biggest pond, at a lower elevation, and pump it up to a smaller pond, at a higher elevation, when needed to increase the pressure to your water systems. Something you will notice over time is that the productivity of water wells downstream of the swale will increase.

They may also produce longer into the summer, and the flow of streams below the swales will be more regular, and have a higher volume. If you want to move water faster, create contours that run against the slope to allow water to travel downhill. It can also be quite effective to simply arrange rocks and logs along a contour. Over time soil, vegetable matter, and other materials will accumulate behind them and passively form a swale.

Swales feed a moderated flow of excess storm water into water courses such as gullys and streams.

How to Build a On-Contour Swale

1. Plan your swale site

You want your swale site to be slightly up-hill from your concerned area.

Take some stakes and run a line between them for the length of your swale.

The Swale must be dug on contour and, have the bottom to be level.

2. Attach the line to the stakes

By doing this you can tell if the land is at the same elevation when using a line level water or laser level.

Your swale may be diagonal across your slope, just stagger your swales so that runoff can’t get by.

3. Pound in stakes once you’ve found the contour for your swale.

A good swale width is wide enough for you to get in and dig.

4. Dig a trench

All the loose dirt goes on the downhill side of the swale, heaped up into what is called a “berm”.

Which holds back the rainwater that fills up the swale.

5. Make sure the bottom of your trench is flat and level
6. Begin filling your swale with Gravel or to stimulate the natural compost like starting with leaves
7. Add the bulk material such as rotting wood
8. Add final materials such as straw
9. Dig more swales and plant your berms!

One can clearly see in the swales pictured here that they are depressed water courses on-contour with gently sloping sides filled with vegetation and other organic matter.

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