The traditional approach to erosion control on construction sites relies upon short-term fixes, which often lead to client complaints in the future. By using simple soil management techniques and plant selection criteria, engineers and landscape architects can significantly reduce the risks associated with soil erosion.
Ignoring erosion control on residential, commercial, and highway construction sites leaves firms open to future liability issues.
Typically, when landscape architects and environmental engineers develop vegetation plans for construction sites, they tend to opt for short-term fixes like degradable erosion control blankets, hydraulic control sprays, or pretty annual plants. These top growth solutions ignore soil conditions and the root system of the plants if any are used at all. Since these techniques do not fix the soil in place, soil erosion problems are inevitable.
According to the USDA’s Natural Resource Conservation Service, long-term soil erosion from construction sites are associated with the following:
- Landslides along roadways
- Issues with water quality due to excessive nutrients and sediments
- Increased flood risk due to high levels of stormwater runoff caused by overly compacted soil
By creating a closed, self-sustaining plant ecosystem as the last finishing step of residential, commercial, or highway construction project, engineers and landscape architects can avoid any liability issues due to the consequences of soil erosion. In addition, the introduction of native plants and trees into the landscape brings aesthetic value to the project. Furthermore, using vegetation for erosion control is usually less expensive than most short-term fixes.
Engineering a Self-Sustaining Plant Ecosystem to Control Soil Erosion
The key to using vegetation to control erosion successfully is to develop an environment for the plants that mimics nature. The benefits of this approach are that the landscape requires little to no maintenance, the plants are twice as robust when compared to those grown using other methods, and the plants are extraordinarily disease resistant. The figure below illustrates a closed-system using plants for erosion control.
Closed self-sustaining plant ecosystem for erosion control
The key elements required to develop a closed plant environment include the following:
- Adequate pore space ensures sufficient space among soil particles to allow air exchange, water movement through the soil, and growth of the root system. In addition, optimal soil pore space decreases the amount of stormwater
- Organic matter provides the nutrients plants need for growth and to stay healthy. The options for adding organic matter to the plant environment include:
- Adding top soil is the most common approach to amending the soil on a job site with organic matter. Unfortunately, topsoil typically contains only 3 percent organic matter, 25 percent water, 25 percent air, and 47 percent mineral, which is not adequate for self-sustaining plant cultivation and growth. Another drawback to using top soil is that it is expensive and time-consuming to add it to the site.
- Compost is another option for adding organic matter to the soil. The issue with using compost is that quality control is difficult since the material may also contain plastics and other debris.
- Using biotic soil amendment (BSA) is the least expensive and most efficient means of incorporating organic matter into the soil since it contains the micro-organisms that break down leaf litter into the nutrients plants need to grow and stay healthy.
- Ensure the soil has mycorrhizae and beneficial bacteria Approximately 90 to 96 percent of plant species depend on mycorrhizae, a fungus that attaches itself to plant root systems. The plant and the fungus develop a symbiotic relationship in which the plant shares nutrients with the fungus and the mycorrhizae increases the ability of the plant’s roots to absorb water and nutrients from the soil. In addition, the fungi increase the plant’s ability to resist disease.
Beneficial bacteria colonies degrade leaf litter into the nutrients needed by the plant. In addition, the micro-organisms also fix nitrogen in the soil.
Selecting Plants to Minimize Erosion Risks
Using native plants to fix the soil in place along roadway slopes adds beauty while eliminating erosion risks
When choosing plants to prevent soil erosion and optimize slope stability, experts recommend using a mix of native trees, grasses, and other plants with deep and dense root systems to fix the soil in place. In addition, the plants should provide mechanisms to prevent excessive water from eroding the soil. The following table outlines the characteristics of the best plants to use to minimize erosion.
The dense root systems of sea oats hold the sand in place to minimize erosion along beaches.
Comparing the Use of Vegetation with Other Means of Erosion Control
Native grasses have dense roots systems to hold soil in place.
While using plants and trees to manage erosion provides aesthetic value, you might wonder how much more effective they are compared to other soil management methods. The following table compares the amount of soil loss and rainwater runoff associated with various erosion control techniques.
This data demonstrates using grass sod is by far the most effective means of reducing soil erosion and storm water runoff. While grass requires periodic mowing, its use is lower maintenance than replenishing soil and less expensive than upgrading stormwater management facilities. For a
no-maintenance approach to using vegetation to control erosion, consider using native perennial wildflowers.
What is your experience using vegetation for erosion control?