Water, wind, and gravity can combine to completely erode a hill or slope’s structural integrity, especially in terrains with steep grades or little vegetation.
No matter your role in the stability project, you can’t allow slope failure. It could cause millions of dollars in landscape, civilian, and property damage.
And you and your professional reputation will be to blame.
Our team recommends using vegetation to support your efforts. But is the quantity and quality of vegetation the primary determinant of a slope’s integrity and stability?
Below are some factors that impact your slope project, common slope stabilization methods, and an analysis of how vegetation impacts slope stability.
What Kinds of Vegetation Stabilizes Slopes?
For slopes of all sizes, vegetation is one of the most common and effective stabilization techniques.
Slopes without any natural vegetation, such as grasses, shrubs, or trees, have nothing naturally connecting the soil particles and area and nothing to reduce the amount of water that flows above and below the surface.
But what kind of vegetation actually supports a slope? Put simply, all vegetation types can provide varying levels of stabilization to a slope.
For instance, grasses, while they don’t have deep root systems, provide some texture and roughness to the surface, helping to prevent runoff channels from developing.
On the opposite side of the spectrum, full-grown trees with extensive root systems can physically stabilize a slope and reduce the impacts of wind and rain.
Mid-size plants, including bushes and shrubs, provide the same benefits to varying degrees depending on their species and physical condition.
How Does Vegetation Prevent Soil Erosion?
So we’ve established what types of vegetation can help stabilize a slope, but how does that process actually work? Below are the five primary ways that plants on a slope can prevent soil erosion and preserve the slope’s integrity.
Interception
One of the primary causes of erosion is rainfall dislodging pieces of soil, which can cause landslides and crusting. Vegetation helps prevent this by intercepting or blocking those raindrops before they arrive at the surface.
Restraint
Another way that vegetation provides slope stabilization is by physically restraining soil particles and holding them together. Root systems and the plants themselves both play a role in this process.
Retardation
Whether it be grasses, small shrubs, or trees, plants serve as a deterrent, slowing down any runoff and preventing large channels from forming. This process is called retardation.
Infiltration
Having plants on a slope increases the available channels, or pathways, for water that lands on the surface to enter the soil. The more vegetation on a slope, the easier it will be for water to infiltrate the soil, making runoff less likely.
Transpiration
While the rate varies greatly depending on the size and species, plants of all sizes absorb water from the soil and use it for general processes. This process, which is called transpiration, reduces the amount of moisture in the soil and, as a result, the chances for oversaturation.
Improving Slope Stability with Vegetation
There are two primary ways that vegetation can improve the integrity and stability of a slope: mechanically improving the slope and reducing the impacts of water.
1). Mechanical Stabilization
Plants and vegetation on a slope help to physically stabilize the soil. While grass and other ground-level foliage can provide some slope stability, most of this stabilization is a result of the roots.
Runoff
Strong, interconnected root systems bind soil particles together, improving the slope’s ability to withstand runoff. The larger the plants and their root systems, the more stability they provide over a larger area.
For instance, a small bush will provide some connectivity and strengthen the soil in a relatively small area, whereas the roots of a fully-grown tree will provide even more stability over a larger area.
Wind
That mechanical stabilization from the roots is particularly important for resisting winds. Soils without any vegetation are susceptible to wind throws. The vegetation mechanically stabilizes the soil and provides cover against the wind.
Vegetation as a slope stabilization method is a long-term solution because it can take many years for a sturdy, widespread root system to grow.
2). Water Stabilization
In addition to physically and mechanically stabilizing a slope, vegetation provides water stabilization. Water-related slope erosion occurs when rainfall creates runoffs and seals soil particles, causing a crust to form.
The water stabilization that vegetation creates works in a few different ways.
Below the Surface
Plants have roots, and roots absorb water from the soil around them. The more vegetation there is on a slope, the more water these plants will absorb, which reduces the likelihood of erosion.
But the water stabilization that plants provide doesn’t only occur below the surface.
On the Surface
On the surface, having vegetation changes the physical landscape, making it rougher and less smooth. Whether it be grass, foliage, or trees, plants increase the roughness and variance of the surface, which slows the velocity and decreases the volume.
Above the Surface
Vegetation, especially trees and plants with lots of foliage, can also intercept rainfall before it ever reaches the surface. During a significant rainstorm, many of the raindrops will land on the vegetation and evaporate back into the air, never touching the surface.
How Vegetation Works with Other Stabilization Methods
In most cases, some type – or types – of vegetation provide some slope stabilization. Plants also work well with other, more involved slope stabilization methods.
For instance, erosion control blankets work especially well when combined with natural vegetation. With an open weave, you can seed the hill through the industrial jute netting for vegetation to grow.
Terraces, which reduce both the velocity and volume of soil and water runoff and control where the water does flow, work best with large plants installed on the flat areas.
Retaining walls are another common stabilization option for complex and steep slopes. There are a variety of types of retaining walls, including natural vegetative and gravity retaining walls. In almost every case, retaining walls function best when paired with vegetation.
Does Vegetation Work for All Kinds of Slopes?
No, vegetation alone isn’t always the perfect solution for all kinds of slopes. While it’s a valuable and often preferred method for its sustainability and natural appearance, there are situations where other methods might be necessary or more effective. Here’s why:
Limitations of Vegetation
Vegetation has its limitations in slope protection. On extremely steep slopes surpassing 45 degrees, the roots of vegetation may lack the strength to effectively anchor the soil, leading to potential instability and erosion. Unsuitable soil conditions, such as loose, dry, or highly erodible soil, may limit the effectiveness of vegetation as it struggles to establish proper anchorage. Additionally, the time required to cultivate mature vegetation with strong root systems may be impractical for situations demanding immediate stabilization. Climate and rainfall play a role too, as arid regions with minimal rainfall may not support dense vegetation growth, while heavy rainfall or fast-flowing water can overwhelm vegetation on steep slopes, compromising its protective capabilities.
How to Stabilize a Slope Combining Slope Protection Methods
Stable slopes are crucial for preventing erosion, landslides, and protecting infrastructure. Fortunately, there’s a toolbox of slope protection methods at your disposal, and often, the most effective approach is a combination of techniques. Here’s a breakdown of some common methods and how they can work together:
Vegetation and Bioengineering
Utilizing vegetation and bioengineering techniques proves to be a multifaceted approach for effective slope management. The implementation of living armor, such as deep-rooted grasses, shrubs, and trees, not only enhances the slope’s stability but also contributes to a natural reinforcement of the soil. This method stands out as a cost-effective, sustainable, and visually appealing solution. Complementing this, erosion control blankets crafted from biodegradable materials like straw or coconut coir serve to cover the slope, preventing soil erosion and facilitating the establishment of vegetation. Together, these strategies form an environmentally friendly and efficient means of slope protection.
Mechanical Reinforcement
Geocells, honeycomb-like grids crafted from polymers, enhance slope stability and prevent erosion by confining soil particles. Ideal for steep slopes, geocells can be filled with vegetation for a seamless natural appearance. Complementing this, terraces and retaining walls serve as effective structures to physically restrain soil on steeper inclines. Terraces break down the slope into manageable sections, while retaining walls offer direct and substantial support. Together, these methods provide versatile and practical solutions for slope management.
Drainage Control
Surface drainage involves the use of ditches and channels to divert water away from slopes, preventing soil saturation and weakening. This proactive measure is effective in maintaining slope stability. Subsurface drainage employs perforated pipes to collect and drain groundwater from within the slope, mitigating pressure buildup and minimizing the risk of landslides. Together, these drainage techniques provide a comprehensive approach to water management, ensuring the long-term integrity of the slope.
Soil Improvement
Soil nailing involves the insertion of long nails into the slope, effectively pinning together soil layers to enhance stability, making it particularly useful for weak or fractured rock slopes. In tandem, shotcrete, a layer of sprayed concrete applied to the slope surface, serves to bind loose soil particles and provides protection against erosion. These techniques work collaboratively to reinforce and fortify slopes, addressing specific challenges such as soil instability and erosion susceptibility.
Combining Methods for Synergy
The key to successful slope stabilization lies in understanding the specific challenges of your slope and choosing the right combination of methods. Here are some examples:
On a gentle slope experiencing mild erosion, a combination of vegetation and erosion control blankets proves sufficient for protection. For steeper slopes subjected to heavy rainfall, a more robust approach involves integrating geocells with subsurface drainage to reinforce the soil and effectively manage water. In the case of a rocky slope with loose soil, employing soil nailing in conjunction with shotcrete becomes essential to stabilize the rock face and prevent soil erosion. Tailoring these strategies to specific slope conditions ensures effective and targeted slope protection measures.
Stabilize Any Slope with Geocell
When it comes to stabilizing a slope, having interconnected, native, and durable vegetation is one of the best tools.
As someone who works with slopes, you know that it isn’t always that simple. For especially steep slopes, or those that are barren and need a solution that will work in the short-term and long-term, vegetation alone won’t work.
For those especially difficult slopes, geocell grids are the most effective solution. By applying lateral forces across the entire system, geocell allows you to enhance the mechanical integrity of a slope.
Geocells will stabilize the slope, improve drainage and water flows below the surface, and help vegetation grow.
Vegetation with Geocell for Extra Slope Support
Our team has installed geocell panels on slopes across the world. During a project evaluation, we can provide more details about the role of vegetation in slope stabilization and help you identify the best solutions for your slope.
Get Expert Advice on Slope Stabilization Using Vegetation with Geocell
For expert advice on slope stabilization using vegetation in conjunction with geocell technology, it’s highly recommended to consult with a professional geocell provider such as Basecore.
Basecore, as a geocell provider, can offer specialized insights into the integration of geocells with vegetation for slope stabilization. Here’s a step-by-step guide on seeking expert advice:
Basecore’s experts will conduct a thorough assessment, considering factors like slope gradient, soil conditions, climate, and local vegetation. Discuss the compatibility of different plant species with geocell technology, and receive recommendations for optimal slope stabilization. Basecore can guide you on geocell design and installation, addressing specific slope requirements. Gain insights into effective maintenance strategies, including watering schedules and weed control, ensuring the long-term success of the geocell-vegetation solution. Obtain a comprehensive understanding of costs and project timelines to plan and budget effectively with Basecore’s expertise.
Want to learn more about how geocells can stabilize any slope? Give us a call at (888)-511-1553.