Rivers and streams are dynamic waterways that are always changing. Part of this change occurs during river bank erosion. While river bank erosion can sometimes deliver favorable results, more often it can have harmful outcomes. Learn more about how and why river bank erosion occurs and methods you can use to stop bank erosion from happening.
What Is River Bank Erosion?
River bank erosion occurs when water wears away at the banks of a river or stream. While river erosion is a naturally occurring process, human impact can increase its rate. Common contributing factors to river and stream bank erosion include:
- Clearing vegetation away from the river bank.
- Intense rainfall.
- River bank saturation from nonriver water.
- Stream and land use management.
- River straightening.
- River redirection around infrastructure or debris in the channel.
- Characteristics of the river bank soil.
The Impact of River Bank Erosion
While almost all rivers will have some amount of healthy river bank erosion, unstable rivers that have large amounts of erosion are cause for concern. At the site of the erosion, issues can include loss of businesses and farmland, which can bring economic hardship to the area. Additionally, erosion can lead to homelessness and migration if people are forced to move. The most significant problem with river bank erosion is mass failure, which occurs when an entire section of the river bank collapses into the river.
Not only does river bank erosion impact the area where the erosion is happening but it can also affect life down the river. Erosion sends extra sediment downstream, which can change the river’s course and disrupt shipping channels.
How to Stop River Bank Erosion
While river bank erosion is an ongoing issue, there are certain river bank control methods available that can slow down or even stop the process. Because erosion occurs in a natural environment on the water, most people prefer to use natural materials to control river bank erosion. When you’re exploring river bank erosion control options, you’ll find everything from temporary and biodegradable materials to permanent solutions.
Vegetation has a major impact on bank erosion. For the most part, river banks that have vegetation erode slower than those without. This is because the roots of the vegetation generally increase the soil’s strength around the river bank, which makes the bank less prone to mass failure. Additionally, plants can act as shock absorbers during heavy rainfall, which also slows the rate of erosion.
While trees and plants that are native to the area are always the best choices when selecting natural vegetation to control river bank erosion, you can also opt for plants known for their expansive root systems and ability to grow near water. The willow tree is one of the best choices for stopping erosion on the river bank because it grows large and durable root systems rapidly.
Soil Erosion Mats
Another common option for erosion control is a soil erosion mat. While these mats are sometimes made with wood fiber or straw, one of the top materials used is coir coconut fiber. This is because coir is strong yet natural. Plus, unlike straw or wood, coir can last in the water anywhere from two to five years.
It’s good for areas that need temporary reinforcement because it offers a period of increased stabilization before eventually biodegrading into the surrounding area. Additionally, coir soil erosion mats won’t harm fish or other wildlife in the water, and it can help vegetation establish along the shoreline for long-term erosion control.
Coir logs are another river bank erosion repair method made using coconut fiber. Coir logs are large in diameter, which makes them ideal for supporting river banks or being used for erosion control on hills, shorelines, and other areas prone to erosion. Even though they’re big, coir logs are easy to place. Once they’re in position, they can help establish vegetation growth. They’ve been effectively used in construction sites, restoration projects, and stabilization areas. Most coir logs will last two to five years before biodegrading.
You can get geotextiles in different materials for a variety of applications. One option you’ll find is woven or nonwoven synthetic fiber geotextiles. Woven geotextiles are incredibly strong, which makes them well-equipped to handle large drainage and erosion control areas. Nonwoven geotextiles are permeable, so they’re ideal for areas where you need drainage and sediment control. Because both woven and nonwoven geotextiles are made with synthetic fibers, they’re UV- and rot-resistant.
You can also find geotextiles made with coir fabric. The fabric comes on rolls that flatten out on the embankment. Unlike synthetic fabric geotextiles, coir geotextiles are biodegradable and won’t harm the environment. Additionally, the roots of vegetation can potentially grow through the fibers and establish plants over the geotextiles.
Tree revetment is a river bank erosion control system that uses small fallen trees anchored horizontally in place along the river bank to prevent erosion. The trees slow the flow of water, which cuts back on the rate of erosion. They also catch sediment in the tree branches and prevent it from flowing down the river. This sediment then creates an effective soil bed to let natural vegetation take root.
For a river bank that needs a strong and permanent erosion control method, gabions might be the best choice. Gabions are large metal baskets filled with stone or concrete rubble. They’re an ideal solution for areas in which a large amount of soil erosion is likely to occur. Although they’re not particularly attractive, you can sink the gabions below the water line at the river. Not only does this make them nearly invisible but it also helps slow the velocity of water flow and train the river to flow in the desired path.
Although river bank erosion has serious consequences, you have several option to control it. When you need to stop river bank erosion, consider implementing one of these effective methods.