You’ve heard the saying, “The best defense is a good offense.” That’s true in sports and erosion control. We'll explore the root causes of soil erosion. Then, we’ll talk about six ways to prevent erosion with road construction, maintenance, and erosion control products.
Erosion control is the process of trying to slow or stop soil from washing or blowing away. It’s most necessary to support and protect infrastructure. For instance, using erosion control on a steep slope could keep it from collapsing on a home.
Roads especially need erosion control. The U.S. has 4.2 million miles of roads, and erosion control helps keeps those roads—and therefore people—safe.1
We need erosion control because nature, seasonal weather, and human activities cause all types of soil erosion. Let’s look at how these factors affect roads.
Water, weather, soil features, terrain, and vegetation all naturally contribute to soil and road erosion.
Rain amount, type, duration, and intensity impact road erosion more than any other factors.2 Prolonged, heavy rains wash away more soil than mere humidity. Acidic rain breaks down rocks faster, especially porous ones like limestone. Even the angle at which raindrops strike the ground can impact how much soil detaches from road surfaces!
Nearby streams, rivers, lakes, and oceans can also render roads unstable, especially during floods or storms. Water that pools on roads can erode them since ponds and puddles keep soil wet and easy to shift. Interestingly, though, salty water seems to make clay less susceptible to erosion.3
During freeze-thaw cycles, water works its way into cracks in the road, then freezes. The cracks expand, the soil weakens, and the road becomes more susceptible to water and wind erosion.
During dry-wet cycles, soil suffers desiccation (aka moisture loss). The dry soil is weaker. And when soil dries too quickly, it sometimes forms a hard crust on the surface that can’t absorb the next rainfall. Instead, rain runs off, creating rills, ruts, and gullies.
Soils can be sand, silt, clay, or a mixture of these called loam. Some soil types resist erosion better than others.
Dense soils with high clay content resist erosion because clay adheres to itself and has high plasticity, so it’ll stretch and mold into new shapes before it erodes. Low-plasticity silt and sand erode easier.4
Soils with varied particle sizes erode less because they have good shear strength. Big particles are harder for wind and rain to move, and their rougher surfaces slow down water flow. Fine soil particles wash away easier.5
Soils with more moisture, salt, and organic matter are usually more stable because these things bond the soil particles together and keep them from washing away.6
Plants along roads absorb water and stem its flow; without them, water flows faster and goes more places, like over the road. Terrain also contributes to erosion. Steep hills and mountains erode faster than flat ground because gravity pulls water and soil off the slope.
When Americans hear “seasonal erosion,” we often think of spring because it’s one of the rainiest seasons for most of the country. However, seasonal erosion occurs year-round.
Spring is prime time to break out erosion control products. That’s because spring is usually rainy—the leading cause of erosion—with fluctuating temperatures. Ice and frost work their way into cracked roads, while warm, sunny days produce snowmelt.
Rural communities often call spring “mud season.” Mud, ruts, washboarding, and potholes can make unpaved rural roads impassable. While dirt and gravel roads bear the brunt of spring weather, paved roads take a hit, too. Heavy rain wears down pavement, worsening existing potholes and causing new ones. Additionally, heavy rain washes debris onto roads, making a mess and wearing surfaces down even more.
On the bright side, spring rain and snowmelt wash corrosive salts off road surfaces. Spring is also the perfect time to see which areas erode most, so you can make an erosion control plan.
You wouldn’t think roads would erode much in hot, dry summers. After all, they’re just sitting there. However, heat and sunlight dry soil into dangerous road dust. They crack both paved and unpaved road surfaces, causing structural shifts over time. And summer is prime time for large, violent storms with damaging rain, wind, and hail.
While temperatures are usually mildest in autumn, fallen leaves stick to roads, making them slick and damaging paved surfaces. They also clog culverts and drainage ditches, causing water to back up onto roads.
Like spring, fall tends to be rainy in many regions, leading to more erosion and potential landslides. And in some U.S. states, fall is hurricane season. High winds, hail, torrential downpours, and storm surges make hurricanes a serious threat to roads and soil.
Water seeps into road cracks year-round. As temperatures drop, it freezes and expands, enlarging cracks and further eroding roads. On unpaved roads, soil freezes and swells upward in a phenomenon called frost heaves.
Chlorides (aka road salt) clear ice, but they can corrode roads and vehicles. Thankfully, you can now find eco-friendly de-icers and erosion control products to replace magnesium chloride.
Road construction and use significantly impacts their erosion resistance—or lack thereof.
Road construction loosens and exposes soil. Many standard construction practices increase the risk of erosion. Consider these examples:
Road maintenance practices also impact erosion. For instance, excessive brush removal or grading without compaction can leave roadways vulnerable to rain runoff.
Traffic pulverizes road surfaces, breaking gravel and dirt clods into smaller pieces that can wash away or become dust. High traffic volume, frequency, and speed increase erosion, as does traffic weight. Heavy equipment and truck traffic damage roads that aren’t built to withstand higher weights and bigger tires.
Excessive deforestation, over-farming, overgrazing, and irresponsible recreation cause land erosion—which then leads to road erosion.
Now, we finally ask the big question: How do we prevent soil erosion? These six tips are great starting points.
Planning is the key to building unpaved roads that resist erosion. Study roads with similar soil types and terrain nearby. What erosion do they have? What solutions work (or not) for them? What design features would improve drainage the most?
Maybe cut-and-fill roads erode more in your area, so you choose an at-grade design. Maybe there’s a steep slope by your road, so you add a retaining wall. Each road is unique, so it’s important to know what causes erosion nearby so you can combat it accordingly.
Erosion control during construction includes things like:
Effective road maintenance helps prevent erosion. For example, repair small potholes and cracks before they become large problems. Grade rills, ruts, and washboards early and recompact the soil. Or, consider seasonal maintenance, like clearing leaves in fall, using non-corrosive de-icers in winter, and sealcoating asphalt in spring.
Whether you’re building a new road or renovating an existing one, proper drainage is one of the best ways to prevent erosion. Some effective drainage systems include:
These drainage systems slow water flow, disperse sediments, and direct water to a suitable outlet. Just be sure they drain to an area that can handle the water without eroding further.
Water conservation systems collect roadwater runoff for use elsewhere, such as irrigation ditches leading to farmers’ fields and constructed wetlands that benefit natural ecosystems. Conservation systems recycle water to avoid waste and prevent floods.
You must remove vegetation during construction, but why not replant it afterward? Grasses, trees, shrubs, and ground-covering species all hold soil into place. Flowers control erosion while attracting pollinators, too.
Choose native plants that work well in the ecosystem and maintain driver safety. For example, plant low-growing species closest to the road so they don’t block drivers’ vision.
Many soil stabilizers exist to strengthen, harden, and protect roads against erosion. However, traditional soil stabilizers like cement, lime, and polymers are increasing in price, and chlorides especially require frequent reapplications. Plus, they can harm the environment.
So, how do you prevent erosion long-term and keep the environment safe?
Perma-Zyme is a sustainable soil stabilizer that’s 100% organic and non-toxic. Its natural enzyme formula bonds clay particles together to create a hard, concrete-like surface that resists erosion for 10 years or more, with little to no maintenance.
With Perma-Zyme, you’ll see a huge decrease in erosion and a huge increase in savings. On average, people save 60% compared to traditional road construction methods.
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