Using stones and plants to combat soil erosion dates back to ancient times. If you’re looking for effective ways to prevent erosion on a slope, we’ve got you covered! In this article, we’ll share valuable tips on how to strategically place rocks on a slope to stop erosion. Whether you’re dealing with a slight incline or a steep slope, we’ll provide you with the guidance you need to succeed. So, let’s dig in and get started!
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Can Stones Be Used on Slopes?
Absolutely! However, before you start hauling boulders up the hill, it’s essential to understand the principles of erosion control on slopes. The Southern California Watershed Recovery and NRCS’s Erosion Control Report is an excellent resource for backyard erosion control. It offers valuable insights into the impact of slope angles on erosion control methods. Here’s a breakdown:
- Slope Under 33% (3 to 1): You have various options for erosion control, including the use of rocks, gravel, and riprap, according to NRCS.
- Slope Ranging From 33% – 50%: Trees and riprap are effective options for erosion control in this range, as suggested by NRCS.
- Slope Over 50%: When dealing with such steep slopes, retaining walls are necessary to create terraced fields. Alternatively, rocks should be partly buried to prevent sliding or rolling.
It’s worth noting that riprap rock is particularly renowned for erosion control along shorelines, culvert channels, and levees where strong water flow is common. The sizes of riprap generally range from 4 inches to 30 inches. Ayres Associates has an excellent riprap rock guide offering more comprehensive information on using riprap to combat erosion.
Do Rocks on Slopes Actually Prevent Erosion?
Absolutely! If placed strategically, rocks on slopes are effective in mitigating erosion. Erosion typically occurs when heavy rainfall or rapid snow melting combines with insufficient ground cover. Factors such as cultivation, fires, or non-productive and loose soil can contribute to a lack of ground cover. By strategically positioning rocks on slopes, you can slow down and redirect the flow of water, thus combating erosion.
It’s astonishing how much rainfall southern and eastern US states sometimes experience. Rainfall of ten to twelve inches within 24 hours is beyond my personal experience. This just goes to show that even a small amount of rainfall can lead to significant soil erosion. A few years ago, we had a torrential downpour of 2 inches in 6 hours, coupled with a clogged downpipe and a freshly planted garden area. It was remarkable how much soil a 5% slope can deposit on your lawn!
Preventing Erosion on Slopes
While rocks alone may not be a complete solution to erosion problems, they are a crucial component of an effective erosion control strategy. Depending on the slope and soil type, a combination of approaches may be necessary. These can include ground cover, hedges, trees, rocks, and grading. Instead of trying to replicate nature, it’s often more beneficial to observe the natural hillsides around your home for inspiration.
Ground Cover that Helps Prevent Erosion
Learning how to place rocks on a slope to stop erosion is just one method of erosion prevention. Another effective approach is using plants or ground cover. If you prefer to maintain a semi-natural slope, consider using stabilizing plants. Here are some popular options:
- Grasses: Buffalo Grass and Kentucky Blue Grass have robust root systems that prevent soil erosion during wind and water runoff. For other grass varieties suitable for your growing zone, check out Southland Organics’ comprehensive guide on using seed and grass for erosion control.
- Legumes: Alfalfa and Red Clover also possess extensive root systems that aid in erosion prevention. It’s best to avoid using sweet clover, as it can grow up to 6 feet tall.
- Broadleaves: Variegated Snow on the Mountain (also known as Bishop’s weed or goutweed) is a resilient ground cover that thrives in our yard, resisting water, weed whackers, rototillers, and even fire. For more suggestions, refer to this useful guide on ground covers for slopes.
It’s worth mentioning that if you have a steep slope and an abundance of ground cover, you might need to enlist the help of goats to control vegetation. Goats are known for their agility, making them excellent “slope lawnmowers”!
Placing Rocks in Drainage Channels
Slopes often have irregular water flow patterns, with varying gradients within the overall slope. Therefore, it’s essential to observe the flow of water during rainfall before determining where to position rocks. One of the most effective erosion control methods is to create dedicated channels that direct water runoff. By identifying and working with existing natural channels, you can assist nature in preventing erosion.
With some observation and planning, these dedicated channels can be modified slightly by widening, deepening, and adjusting the slope to guide the water where you want it to go. It is crucial to strike a balance: the idea is to slow down the water’s flow, even within a dedicated channel. Leaving some bumps and gentle curves in the channel is advisable.
To reinforce the channels, consider lining them with landscaping fabric and securing it with river rock or riprap. Alternatively, you can place rocks directly in the channels without using fabric. For steeper slopes, burying the rocks partially in the soil will ensure they stay in place.
A key point to remember is that water will naturally flow through the gaps between the rocks, which is why landscaping fabric is necessary. Without it, the water may erode the soil beneath the rocks, causing them to sink or move downhill. Additionally, skipping the fabric may lead to increased weed growth, potentially obstructing or slowing down drainage.
Placing Rocks to Control Slope Erosion
Most slopes aren’t uniform or consistent, as they are shaped by natural processes and the last ice age. Take the time to observe rainfall and the resulting runoff. This will help you identify areas that would benefit from strategic rock placement to slow down or divert the flow of water.
It’s crucial to note that relying solely on ground cover may have its drawbacks. While plants effectively hold soil in place, excessively dense root systems can hinder absorption, causing water to rush down the slope even faster. By strategically positioning individual rocks, riprap, or gravel collections, you can impede, redirect, and disperse water flow, effectively combating erosion.
Placing Rocks at the Base of the Slope
Regardless of the methods employed to guide water to the bottom of the slope without eroding the topsoil, it’s essential to address runoff when it reaches the base. A French drain or blind drain installed perpendicular to the garden slope can be used to absorb or carry runoff away from the area.
By constructing a rock retaining wall or placing large stones at the foot of the drain channels, you can dissipate the force of the water coming down the hill. This strategically placed stone barrier helps protect the flatter sections of your yard, ensuring water is absorbed into the French drain and is directed away from your property.
If you’re interested in learning more about French drains, you can find step-by-step instructions at wikihow.com/Build-a-French-Drain.
It’s worth noting that French drain (or curtain drain) designs are limited only by imagination, as there are numerous drainage ideas available online. Most designs incorporate perforated pipes and ample use of rocks. The retaining wall for a French drain can be made of rock, brick, or concrete. The purpose of the wall is to temporarily halt the water, allowing it to be absorbed into the drain.
Terraced Erosion Control and Gardening
Building terraces on slopes is an excellent method for preventing erosion while maximizing land utilization. Terracing has been practiced worldwide for centuries to optimize the use of sloping land. However, it requires considerable time and effort.
Traditionally, terracing involves creating wide and flat sections of the hillside. A rock retaining wall is built along the edge of each section, which is then leveled to create usable garden or field space. The garden area is gently sloped to allow for proper drainage. Some terrace walls may have gaps to allow excess water to escape. Most terrace rock walls follow the natural contours of the hillside, resulting in a softer and more natural appearance that requires less work.
Learning how to place rocks on a slope to prevent erosion is an invaluable skill. Rocks are a fantastic addition to your erosion prevention toolkit! They are durable, resistant to decay, and rarely shift when properly positioned. Moreover, if you live in an area with abundant rocks, they are a cost-effective option. (Any farm with rocks will likely have a ready supply of instant riprap!)
Keep in mind that rocks used in landscaping, especially on slopes, require hard work, heavy lifting, and time. Motorized equipment and significant effort may be necessary. However, the results can be incredibly effective in preventing soil erosion and surprisingly attractive.
If you have any questions or tips on using rocks to combat erosion or how to place rocks on a slope to prevent erosion, we’d love to hear from you. We welcome input from fellow homesteaders, rockery gardeners, and erosion control enthusiasts!
Thanks for reading, and have a fantastic day!
To learn more about erosion control and other topics, check out 5 WS.