As the world faces increasing challenges with water management, swales have emerged as a promising solution for addressing both flooding and drought. These shallow, vegetated depressions can effectively capture and store rainwater, mitigating runoff and erosion while recharging groundwater supplies. Embarking on a swale excavation project can be a rewarding endeavor, but it requires careful planning and execution. By understanding the principles of swale design and construction, you can create a functioning and sustainable water management system on your property.
The first step in digging a swale is to determine its size and location. Consider the slope of the land, the volume of water you want to capture, and the available space. Swales can be designed to accommodate various flow rates and volumes, from small-scale residential applications to large-scale agricultural projects. Once you have determined the dimensions, stake out the swale’s outline using flags or stakes. This will serve as a guide for the excavation process.
The next step is to remove the topsoil and vegetation within the staked area. This layer can be composted or spread elsewhere on your property. The depth of the swale will vary depending on the desired storage capacity and the soil conditions. Generally, a depth of 1 to 2 feet is sufficient for most residential applications. Use a shovel or excavator to dig the swale, ensuring that the bottom is level and free from any obstructions. The sides of the swale should be gently sloping, with a maximum slope of 3:1, to prevent erosion and facilitate vegetation establishment.
Site Assessment
Before you start digging, it’s important to assess your site to make sure that it’s suitable for a swale. Here are some things to consider:
Slope
The slope of your site will determine the depth and width of your swale. A steeper slope will require a deeper and wider swale to slow down the flow of water. The ideal slope for a swale is between 2% and 5%. If your site is steeper than 5%, you may need to consider using a different type of water management system, such as a terrace or a contour swale.
Soil
The type of soil on your site will also affect the design of your swale. Sandy soils are more permeable than clay soils, so they will allow water to infiltrate more quickly. This means that you may need to dig a deeper swale in sandy soil to achieve the same level of water retention. Clay soils are less permeable, so they will hold water for a longer period of time. This means that you may need to dig a shallower swale in clay soil to prevent waterlogging.
Vegetation
The vegetation on your site can also affect the performance of your swale. Swales that are planted with vegetation will be more effective at slowing down the flow of water and filtering pollutants. However, it’s important to choose plants that are tolerant of wet conditions. Some good choices for swale plants include:
| Plant | Description |
|---|---|
| Sedges | These grass-like plants are tolerant of wet conditions and can help to filter pollutants. |
| Rushes | These plants are similar to sedges, but they have hollow stems. |
| Irises | These showy flowers are tolerant of wet conditions and can help to attract pollinators. |
Marking the Swale
Once you have determined the location of your swale, it is time to mark it out. This will help you to dig it in the correct location and size.
To mark the swale, you will need:
- String or twine
- Stakes or flags
- Measuring tape or ruler
To mark the swale, follow these steps:
- Determine the width and depth of the swale. The width of the swale should be between 2 and 4 feet, and the depth should be between 6 and 12 inches.
- Lay out the string or twine along the path of the swale. Use the stakes or flags to mark the corners of the swale and to keep the string in place.
- Measure the distance between the stakes or flags to ensure that the swale is the correct width and depth.
- Once the swale is marked out, you can begin digging. Remember to dig the swale at a gradual slope so that water will flow through it easily and prevent erosion.
Excavating the Swale
To excavate the swale, follow these steps:
1. Lay Out the Swale: Decide the desired orientation and shape of the swale. Using stakes and string, outline the swale’s perimeter and center.
2. Remove Topsoil: With a shovel or excavator, remove the topsoil layer to depths ranging from 6 to 12 inches, depending on the desired depth of the swale. Consider storing the topsoil nearby for use later.
3. Slope the Sides: Use a hoe or shovel to carefully slope the sides of the swale. The slopes should be gradual, typically ranging from 2:1 to 4:1 (vertical:horizontal). This gradual slope allows water to flow through the swale while preventing erosion.
4. Create Check Dams: If necessary, create check dams within the swale to slow down water flow and prevent erosion. Check dams can be made from various materials such as logs, stones, or straw bales.
5. Align with Contours: Ensure that the swale follows the natural contours of the land. This will help direct water where it is needed and minimize erosion.
6. Backfill with Soil: Once the swale is excavated and shaped, backfill it with the previously removed topsoil. This layer will provide a growing medium for vegetation.
7. Seed and Plant: To stabilize the swale, seeded it with a native grass or plant mixture. This vegetation will help control erosion, filter sediment, and provide habitat for wildlife.
| Slope Ratio | Description |
|---|---|
| 2:1 | Relatively steep slope for swales designed to manage large volumes of water or in areas with steep gradients. |
| 3:1 | Moderate slope suitable for a wide range of swale applications. |
| 4:1 | Gradual slope recommended for swales in areas with gently sloping terrain or where erosion is a concern. |
Shaping the Swale
The best way to shape a swale is to use a combination of hand tools and machinery. Start by marking out the general shape of the swale with a string or rope. Then, use a shovel or hoe to remove the top layer of soil, creating a shallow trench. Next, use a pick or mattock to break up the subsoil, creating a deeper trench. Finally, use a rake or hoe to smooth out the sides of the trench and create a gentle slope.
Considerations:
- The slope of the swale should be gradual, no more than 5%. This will help to prevent erosion and allow water to flow slowly through the swale.
- The depth of the swale will depend on the amount of water you need to manage. A deeper swale will hold more water, but it will also be more difficult to create.
- The width of the swale will also depend on the amount of water you need to manage. A wider swale will hold more water, but it will also be more difficult to dig.
Once you have shaped the swale, you can plant it with vegetation to help stabilize the soil and prevent erosion. Native grasses and sedges are good choices for swales, as they are well-adapted to wet conditions. You can also plant trees and shrubs in the swale, but be sure to choose species that are tolerant of wet soils.
Swale Dimensions:
| Characteristic | Minimum | Maximum |
|---|---|---|
| Slope | 1% | 5% |
| Depth | 6 inches | 2 feet |
| Width | 2 feet | 10 feet |
Berming the Swale
Berming is the process of creating a small earthen berm, or ridge, on the downslope side of the swale. This berm helps to slow down and spread out the water as it flows through the swale, preventing erosion and increasing infiltration. Berming is a relatively simple and inexpensive way to improve the performance of a swale.
Steps for Berming a Swale
- Use a shovel or hoe to create a small mound of soil on the downslope side of the swale. The berm should be about 6-12 inches high and 2-3 feet wide.
- Compact the soil in the berm by tamping it down with your feet or using a hand tamper.
- Plant vegetation on the berm to help hold the soil in place and prevent erosion. Grasses, shrubs, and small trees are all good choices.
- Berm the entire length of the swale, or at least the areas where erosion is most likely to occur.
- Tips:
- If the swale is very steep, you may need to create a series of berms along the length of the swale.
- Berms can be made of any type of soil, but clay soils work best because they hold water well.
- Berms can be seeded or planted with vegetation to help hold the soil in place.
- Berms can be used in conjunction with other swale treatments, such as check dams and riprapping.
Invasive Species Control
Bucket Brigades
These can be used to eliminate small patches of invasive species. Form a line with buckets and fill them with the invasive species. Pass the buckets down the line and dump them in a designated disposal area.
Removal Events
Organize group events to remove invasive species from a specific area. Provide volunteers with tools and instructions to effectively remove the species. Follow up with regular monitoring to prevent regrowth.
Targeted Herbicides
In cases where manual removal is not feasible, targeted herbicides can be used to eliminate specific invasive species. Choose herbicides that are selective and will not harm non-target plants. Consult with a professional before using herbicides.
Mechanical Control
Mechanical methods, such as mowing, brush cutting, or prescribed burns, can be used to control the spread of invasive species. These methods must be used carefully to avoid damaging native vegetation.
Biological Control
In some cases, it may be possible to introduce natural predators or parasites that feed on invasive species. This method requires careful consideration and should only be implemented with expert guidance.
Grazing
Livestock grazing can be used to suppress the growth of invasive species and promote the establishment of native plants. Grazing must be managed carefully to prevent overgrazing and damage to native vegetation.
Plantings and Landscaping
Swales can be landscaped to enhance their aesthetic appeal while also supporting ecological functions. Here are a few landscaping ideas:
Flowering Plants:
Native flowering plants are a great choice for swales as they provide nectar and pollen for pollinators. Consider species such as coneflowers, black-eyed Susans, and milkweed.
Grasses and Sedges:
Grasses and sedges add structure and stability to swales. They help slow down water flow and filter pollutants. Suitable species include native grasses like switchgrass and big bluestem, or sedges like carex and juncus.
Trees and Shrubs:
Trees and shrubs can provide shade, reduce erosion, and create wildlife habitat. Plant native species that are adapted to the local climate and soil conditions.
Rain Gardens:
Rain gardens are designed to capture and infiltrate rainwater. They can be incorporated into swales to improve water quality and reduce runoff. Plant rain gardens with a mix of native plants that tolerate wet conditions.
Planting Guide:
To ensure successful plantings in swales, follow these guidelines:
| Depth | Plant Type | Spacing |
|---|---|---|
| 0-6 inches | Groundcovers | 12-18 inches |
| 6-12 inches | Grasses and Sedges | 12-24 inches |
| 12-18 inches | Flowering Perennials | 18-36 inches |
| 18-36 inches | Shrubs | 3-5 feet |
| Over 36 inches | Trees | 10-20 feet |
Remember to water your plants regularly during the establishment period and mulch around them to retain moisture and suppress weeds.
Maintenance and Monitoring
Maintenance
Regular swale maintenance is crucial to ensure optimal functionality and longevity. Here are essential maintenance tasks:
1. Sediment Removal
As water flows through the swale, sediment may accumulate. Periodically remove this sediment to maintain water flow capacity and prevent clogging.
2. Vegetation Management
Vegetation growth can obstruct water flow and damage the swale’s structure. Trim or remove excess vegetation to maintain water conveyance efficiency.
3. Bank Stabilization
Over time, swale banks may erode due to heavy rainfall or flooding. Install erosion control measures such as riprap or vegetation to protect the banks and prevent sediment loss.
4. Water Quality Monitoring
Periodically monitor water quality in the swale to assess its effectiveness in reducing pollutants. This helps identify any potential issues and take corrective action if necessary.
5. Infrastructure Inspection
Inspect all infrastructure associated with the swale, such as inlets, outlets, and drop structures. Ensure they are in good condition and operating properly.
6. Wildlife Management
Monitor the area for wildlife activity and take measures to minimize any potential conflicts. For example, install fencing or create buffer zones to prevent wildlife from entering or damaging the swale.
7. Structural Integrity Assessment
Regularly assess the structural integrity of the swale, including its sides, bottom, and any retaining walls. Repair any damage promptly to maintain the swale’s functionality.
8. Additional Considerations
Consider the following additional factors during maintenance:
| Factor | Considerations |
|---|---|
| Seasonal Conditions | Adjust maintenance activities based on season and weather conditions to minimize erosion and maximize effectiveness. |
| Land Use Changes | Monitor changes in land use in the contributing area and adjust swale maintenance accordingly to address any potential impacts. |
| Legal Requirements | Comply with all applicable regulations and permit requirements related to swale maintenance and water quality management. |
Benefits of Swales
1. Erosion Control
Swales help slow down and absorb rainfall, reducing the amount of water that runs off and erodes soil. The vegetation in swales also helps hold the soil in place.
2. Stormwater Management
Swales can store and release stormwater gradually, reducing the risk of flooding. They can also help improve water quality by filtering out pollutants.
3. Groundwater Recharge
Swales allow rainwater to soak into the ground, which recharges groundwater aquifers.
4. Wildlife Habitat
Swales provide habitat for a variety of plants and animals, including birds, frogs, and insects.
5. Aesthetic Benefits
Swales can be designed to be both functional and aesthetically pleasing. They can add beauty to a landscape and provide a place for people to enjoy nature.
6. Cost-Effectiveness
Swales are a relatively inexpensive way to manage stormwater and erosion. They require minimal maintenance and can last for many years.
7. Ease of Installation
Swales can be installed by hand or with the help of a small excavator. They are a simple and straightforward solution for stormwater management.
8. Sustainability
Swales are a sustainable way to manage stormwater and erosion. They use natural processes to slow down and absorb rainfall, and they do not require the use of chemicals or other harmful substances.
9. Additional Benefits
- Improved water quality: Swales can help improve water quality by filtering out pollutants, such as sediment, nutrients, and bacteria.
- Reduced flooding: Swales can help reduce flooding by storing and releasing stormwater gradually.
- Increased groundwater recharge: Swales can help increase groundwater recharge by allowing rainwater to soak into the ground.
- Wildlife habitat: Swales can provide habitat for a variety of plants and animals, including birds, frogs, and insects.
- Aesthetic benefits: Swales can be designed to be both functional and aesthetically pleasing. They can add beauty to a landscape and provide a place for people to enjoy nature.
- Cost-effectiveness: Swales are a relatively inexpensive way to manage stormwater and erosion. They require minimal maintenance and can last for many years.
| Benefits | Description |
|---|---|
| Erosion control | Reduce the amount of water that runs off and erodes soil. |
| Stormwater management | Store and release stormwater gradually, reducing the risk of flooding. |
| Groundwater recharge | Allow rainwater to soak into the ground, which recharges groundwater aquifers. |
| Wildlife habitat | Provide habitat for a variety of plants and animals, including birds, frogs, and insects. |
| Aesthetic benefits | Add beauty to a landscape and provide a place for people to enjoy nature. |
| Cost-effectiveness | Are a relatively inexpensive way to manage stormwater and erosion. |
| Ease of installation | Can be installed by hand or with the help of a small excavator. |
| Sustainability | Are a sustainable way to manage stormwater and erosion. |
10. Finish the Swale and Plant Vegetation
Once you have shaped the swale and lined it with organic matter and soil, the final step is to plant vegetation. This vegetation will help to hold the soil in place and prevent erosion. Choose plants that are native to your area and that are adapted to the conditions of the swale. You may also want to consider planting a variety of plants to create a diverse ecosystem.
Here is a table with some tips for planting vegetation in your swale:
| Tip |
|---|
| Plant in the fall or spring, when the weather is mild. |
| Use native plants that are adapted to the local climate. |
| Plant a variety of plants to create a diverse ecosystem. |
| Water the plants regularly, especially during the first year after planting. |
| Mulch around the plants to help retain moisture and suppress weeds. |
How To Dig A Swale
Swales are shallow, vegetated channels that are used to manage stormwater runoff. They can be used to slow down the flow of water, reduce erosion, and improve water quality. Swales are typically dug by hand, using a shovel and a level.
To dig a swale, first mark out the location of the swale with stakes and string. The swale should be at least 4 feet wide and 6 inches deep. The slope of the swale should be no more than 2%.
Once the location of the swale has been marked out, begin digging the channel. Use a shovel to remove the sod and soil. Once the channel has been dug, smooth out the sides and bottom of the channel with a rake.
Once the swale has been dug, plant vegetation in the channel. Vegetation will help to stabilize the soil and prevent erosion. Good choices for vegetation include grasses, sedges, and rushes.
People Also Ask About How To Dig A Swale
What is the best time to dig a swale?
The best time to dig a swale is in the fall or spring, when the ground is soft.
How often should I mow the vegetation in my swale?
The vegetation in your swale should be mowed once or twice a year, to keep it from getting too tall and blocking the flow of water.
Can I use a swale to drain my basement?
Yes, a swale can be used to drain your basement, but it is important to make sure that the swale is properly designed and installed.
How much does it cost to dig a swale?
The cost of digging a swale will vary depending on the size and complexity of the swale. A simple swale can be dug for a few hundred dollars, while a more complex swale may cost several thousand dollars.
