Water erosion along creek banks, river banks, or lake shorelines can cause damage to properties as well as the environment. When it comes to riverbank stabilization, there are many different methods available. Many methods involve using synthetic materials, but there are also natural options. Options that involve natural and biodegradable materials can enhance the appearance of a riverbank as well as benefit the ecosystem and wildlife.

riverbank with some erosion

How to protect against riverbank & shoreline erosion

Some bank protection techniques include the use of rip rap (hard armoring), planting vegetation, and using geotextile bags like TrapBag. Often, a combination of methods is the best solution.

Riverbank erosion can be prevented by avoiding harmful actions that lead to erosion. Some of these include:

  • Removing vegetation
  • Improper land use
  • River redirection

The first method to stop riverbank erosion is natural vegetation. Natural vegetation has a massive impact on a riverbank. The plants form deep root systems which help to hold soil in place and protect it from being washed away. Plants can also absorb the shock of heavy rainfall. When using this method, make sure to use plants and trees native to the area. Some plants have more expansive (and therefore, helpful when it comes to erosion) roots systems than others.

natural marshland

“The root system helps hold the soil together and increases the overall bank stability by its binding network structure, i.e., the ability of roots to hold soil particles together. Second, the exposed vegetation (stalks, stems, branches, and foliage) can increase the resistance to flow and reduce the local flow velocities, causing the flow to dissipate energy against the deforming plant rather than the soil. Third, the vegetation acts as a buffer against the abrasive effect of transported materials. Fourth, close-growing vegetation can induce sediment deposition by causing zones of slow velocity and low shear stress near the bank, allowing coarse sediments to deposit. Vegetation is also often less expensive than most structural methods; it improves the conditions for fisheries and wildlife, improves water quality, and can protect cultural/archeological resources.” — US Army Corps of Engineers

Bioengineering can be dependent on weather conditions and local wildlife.

hard armored riverside

Another method is Riprap or hard armoring. Hard armoring involves the layering of rocks along the bank in order to protect it from water erosion. This, however, leads to problems. Riprap causes the speed of the current to increase because it reduces friction points. It also causes the deflected water to hit other exposed areas of the riverbank and worsen erosion there. Essentially, installing riprap in one area of a river or stream will necessitate its installation along the entire bank or shoreline.

rip rap rocks

It also negatively impacts the ecosystem.

“Another aspect of riprap is its considerable effect on wildlife, specifically fish that live in and utilize streams and rivers where eroding banks have undergone armoring. While erosion can cause potential problems for fish, especially in high-silt locations, the installation of riprap leads to other, more significant, issues. When riprap is the primary or only form of riverbank stabilization measure, the end result is typically a uniform, smooth channel, with no complexity.” — FEMA.gov

Riprap can also be costly to implement.

The best way to protect a riverbank from erosion is using geotextile bags — like the TrapBag barrier system — which can stabilize the riverbank for temporary or permanent purposes.

inlet channel with rip rap armoring along both sides

Using natural materials to protect riverbanks

Does planting vegetation work?

Planting vegetation does typically work to help prevent streambank erosion. Sometimes weather conditions, wildlife, or the severity of the erosion can require the use of a combination of methods.

Do hard armoring or rip rap rock work for river banks?

“Riprap, or hard armoring, is the traditional response to controlling and minimizing erosion along shorelines or riverbanks. As demonstrated by past multiple disasters in Washington State, the U.S. Department of Homeland Security’s Federal Emergency Management Agency (FEMA) has provided funding assistance for the repair to these riprap facilities.*1 The very nature of having to repair these facilities counters the popular engineering belief that riprap is the best solution for mitigating stream bank erosion.“ — FEMA.gov

In the past, riprap has not only failed, but led to worsened conditions and environmental damage. When compared with the use of geotextile bags like TrapBag, riprap is more expensive and less effective.

TrapBags used to shore up riverside

Using TrapBag geotextile erosion control bags for riverbank erosion

The TrapBag® barrier system can be applied to stabilize a riverbank for temporary, semi-permanent or even permanent purposes when filled with concrete. Since the TrapBags® are stackable, the height of the riverbank is not a factor — this is key for tall riverbanks where rip rap/hard armoring is not an option.

The installation of a TrapBag® barrier system is much less costly and time consuming compared to other methods. Another benefit of using TrapBags® is that you can cover them with vegetation which not only creates a more natural look but it increases the stability of the riverbank.

TrapBag® is a series of pentagon-shaped bags that are sloped on one side, vertical on the opposite side and open at the top for filling. Each of the cells are connected side by side like an accordion, each cell has a common wall with the next cell, and are collapsed during storage and deployment. The cells are made of high-strength textile. Each of the cells are self-contained yet rely on the next cell for added strength. If one of the cells is compromised, it will not affect the rest of the barrier, which will remain standing strong.

TrapBag® uses 40% less fill material than a stacked sandbag wall, but more importantly a single 100 foot section of 4ft high TrapBag® replaces approximately 8,000 sandbags making TrapBag® Barriers an excellent alternative to small and large sandbags. TrapBag® Barriers can be filled with sand, washed gravel, or concrete. Avoid filling with silt, clay, or rocks greater than 2 inches across.

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