What Techniques Does Permaculture Offer For Soil Erosion Control?

“Hi there, I’m dealing with some pretty severe soil erosion on a slope in my backyard. The rainwater just flows down the hill, taking the topsoil with it. I’m really interested in using permaculture techniques to control this problem, but I’m not sure where to start. Can you suggest some specific strategies that would work for a situation like mine? The slope is pretty steep, and the soil is loamy but starting to compact. Any advice would be much appreciated.” Thanks, Samantha, Queenstown, New Zealand.

Understanding Soil Erosion and Why It Matters

Soil erosion is one of those garden problems that can sneak up on you, yet once it’s underway, it can be a real headache. Basically, erosion happens when water or wind strips away your topsoil, leaving the ground bare and struggling to support plant life. That topsoil is pretty important—it’s where all the good stuff lives, like nutrients and organic matter, so when it disappears, your plants don’t stand much of a chance.

Samantha, since you’re dealing with a steep slope, your erosion problem is probably most noticeable after a heavy rain, right? That’s because water gathers momentum as it flows down a slope, washing away more and more soil as it goes. And I bet it’s even more frustrating if you’ve put effort into planting, only to see everything washed downhill. But don’t worry, there are some solid (pun intended) permaculture techniques that can help you get this under control.

The Permaculture Approach to Soil Erosion

Permaculture is all about working with nature, not against it. So, instead of trying to fight the erosion with heavy, expensive measures (like retaining walls), you can use nature-inspired solutions to slow down rainwater, build the soil, and encourage plant growth. When you follow permaculture principles, you’re not just stopping erosion; you’re actually creating a healthier, more resilient ecosystem.

Key Concepts for Erosion Control

• Contouring: This is all about shaping the land to slow down and distribute water. Think of it like giving your hill a few speed bumps to decrease the water’s momentum.
• Diversifying Plant Life: Plants with deep root systems help anchor the soil, reducing the chance of erosion.
• Mulching: A good layer of mulch does wonders for protecting the soil from erosion, while also improving soil health.

Let’s take a closer look at how you can put these ideas to work in your backyard.

Swales: The Backbone of Soil Water Management

One of my favorite techniques for controlling erosion on slopes is to use swales. Swales are shallow, level-bottomed trenches dug along contour lines (these are the imaginary lines on a slope where elevation remains consistent). Basically, you’re creating little channels that help slow down and capture water.

How to Create a Swale

Samantha, to get started, you’ll need to identify the contour lines on your slope. You can do this with some simple tools like an A-frame level or by using a laser level for more accuracy. Mark out where you want your swales before digging—this will give you a visual guide.

Once your contour is marked out, dig a trench that’s a few inches to a foot deep (depending on how much water you’re trying to manage) and level it out. Use the soil you excavate to build a berm (a small mound) on the downslope side of the swale. This berm helps to stop and soak water into the ground. The idea is for the water to accumulate in the swale after a rain, and slowly percolate into the soil rather than rushing downhill.

And remember, don’t just leave your swale to its own devices—plant it! Grasses, legumes, or other ground covers work well because they help hold the soil in place. Over time, the plants help to strengthen the swale and make it even more effective at reducing erosion.

Advanced Swale Tips

If you’re feeling a little more adventurous, you can connect multiple swales like a chain running down the slope. This way, if one swale overflows, the water can move to the next one, and so on. This cascading effect can be highly effective on steeper slopes like yours, Samantha.

Terracing: Stepping Down the Erosion

If your slope is really steep, then terracing might be a better option for you. Terracing is like creating a series of ‘stairs’ on your slope, providing flat surfaces where water can spread out instead of rushing straight down. This technique has been used for centuries in areas with difficult terrain, so you know it works!

The Basics of Terracing

To create a terrace, you’ll need to dig into the slope to make a flat surface, then use some of the dug-out soil to form a retaining wall on the front edge of the terrace. Think of it like building a series of small garden beds that run along the contour of the hill. Each terrace acts as a mini-level area that catches and holds water, slowing down the rate of erosion.

Depending on the steepness of your slope, you might need to build several terraces, each a few feet tall. It’s a bit more work upfront, but once it’s in place, you’ll find that it drastically reduces erosion. Plus, it gives you some extra growing space—you can easily turn each terrace into a productive garden bed.

Choosing Plants for Terraces

When it comes to picking plants for terraces, choose ones with deep or fibrous roots. Ground covers like creeping thyme or herbs with deep roots like rosemary can help secure the soil while adding beauty and function to your terrace. Even better, think about perennial crops like strawberries—they’ll help hold the soil in place while giving you delicious fruit at the same time.

And don’t forget about trees! Small fruit trees or shrubs that are adapted to hillside planting can also work well, anchoring the soil even more effectively. Just make sure to space them out so each tree has enough room to grow without disturbing the soil structure of your terraces.

Mulching: Nature’s Blanket for Soil Protection

Let’s talk mulch—this stuff is practically magic for soil conservation. By covering your soil with a thick layer of organic material like straw, leaves, or wood chips, you’re providing a protective blanket that shields your soil from the harsh effects of wind and rain.

Why Mulching Works

Mulch does an outstanding job of absorbing the impact of raindrops, which helps prevent the soil from compacting and eroding. It also soaks up and holds moisture, reducing the amount of water that runs off your slope. With a good layer of mulch in place, your soil stays protected, and your plants enjoy a steady supply of water as the mulch slowly decomposes.

How to Apply Mulch

Start by spreading mulch in a uniform layer over the areas of bare soil, at least 3-4 inches thick. Avoid piling it too close to the base of your plants to prevent rot, but make sure you’ve covered any exposed soil generously. This will act as a buffer zone, slowing down water flow and allowing it to sink into the ground instead of washing away your soil.

And here’s a little trick for you, Samantha—after spreading the mulch, consider planting a cover crop right into it. Something like clover or vetch adds another layer of erosion control and improves soil fertility as it grows. The mulch gives the seeds a cozy spot to germinate, while they, in turn, lock down the soil even better.

Planting Strategies: Rooting Out Erosion

Now, let’s get into the nitty-gritty with your plants. Diversifying what you grow on that slope can do wonders for controlling erosion. By choosing a mix of deep-rooted plants, spreading ground covers, and perennial plants, you’ll help stabilize the soil.

Deep-Rooted Plants

Plants with deep roots can extend far below the soil surface, acting like anchors that hold the soil in place. Grasses such as switchgrass or prairie dropseed are excellent choices here, as their roots can reach several feet down.

Similarly, well-chosen trees and shrubs, like elderberries or willows, can also play a massive role. Their extensive root systems not only provide an incredible natural barrier against erosion but bring several other benefits. The deep roots help break up compacted soil, allowing more water to infiltrate the ground, which will really help with your loamy soil, Samantha.

Ground Covers for Coverage

A diverse set of ground covers will work in tandem with your deeper-rooted plants. Creeping plants like clover, thyme, or even mint can spread quickly over a slope, providing vital coverage that prevents the topsoil from being washed away.

The beauty of ground covers is that they work to smother weeds, too, which means less maintenance for you. Plus, the way they knit together across the soil surface means that it can resist even heavy downpours far better than bare soil.

Weathering the Storms: Dealing with Severe Rainfall

When those heavy rains hit, they can really test the stability of your slope. But there’s a way to pre-empt those storms before they can spell disaster for your garden. A permaculture-friendly solution here involves creating overflow paths and diversions.

How to Create Overflow Paths

The idea is to design overflow channels that direct excess water safely out of harm’s way. On a slope, this could mean using swales, ditches, or simple diversion drains to guide water away from critical areas and into a place where it can do less damage—like a marshy area or a seasonal pond.

For example, suppose you’ve got a swale or a terraced garden set up already. In that case, you can use the same principles to add a diversion channel that connects each step, gradually moving any excess water down and away—rather than letting it gather force as it cascades to the bottom.

And don’t forget to include some plantings along these pathways. Not only will they help disguise the channels, but they’ll also provide further erosion control by slowing down the water flow.

Composting and Soil Health: A Foundation for Permanent Soil Structure

Once you’ve got the physical barriers and plantings set up, think about how you can improve your soil quality. Healthy soil is more resilient and better able to withstand erosion forces. That’s where composting and organic matter come into play.

Building Soil with Compost

Adding compost to your soil enriches it with nutrients, enhances its structure, and supports the life forms (like earthworms and microbes) that help maintain it. And the more organic matter you add, the more spongy your soil becomes, enabling it to absorb and hold more water. This is particularly helpful on slopes where quick water runoff is a problem.

You could start by adding compost directly to the planting areas on your terraces or, better yet, mulch with composted materials to kill two birds with one stone—protecting the soil and improving it simultaneously.

Living Mulch: A Dual-Purpose Solution

Speaking of multitasking, consider using a living mulch in the form of cover crops. These are plants like rye or clover that grow quickly and provide a protective cover for your soil. When they die back, they decompose and give your soil a big organic boost.

This can be especially handy on your slope, Samantha, as living mulches can continue to grow even in tricky spots, giving your soil the defense it needs without requiring much input. When spring comes, you can just turn the crops under for an added nutrient punch.

Troubleshooting and Maintenance

Even the best erosion control systems need a little TLC. Keep an eye on your slope, especially after those hefty rainstorms, to make sure everything is holding up. Look for areas where water is pooling or where soil might be getting loose.

What to Watch For

• Patches of Exposed Soil: These are a big red flag signaling that erosion is starting to take hold. Add more mulch or replant ground covers here as soon as possible.
• Water Pooling: If water is pooling in or around your swales or terraces, it could signal that it’s time to adjust your system. Consider adding overflow channels or increasing soil drainage.
• Shifting Berms or Terraces: If you notice your terraces or berms are starting to shift, reinforce them by adding more soil or rocks, or use deep-rooting plants to help stabilize the area further.

If you find that certain areas of your garden are struggling more than others, it might just be a case of needing some adjustments. Maybe another swale, a thicker layer of mulch, or even rethinking plant choices could be the key to getting everything working smoothly.

Final Thoughts…

Samantha, thanks for reaching out with your question. Tackling soil erosion on a slope is always a challenge, but with these permaculture techniques, you’ll be well on your way to a lush, healthy, and stable garden. Putting in the initial effort to create swales, terraces, and to mulch extensively will pay off in the long run, helping you protect the soil and work in harmony with the land. Remember to keep an eye on things and make adjustments as you go—it’s all about observing and interacting with your garden over time. Good luck with your project, and I’m thrilled you’re taking the permaculture path. You’ve got this!