As climate change intensifies the frequency and severity of extreme rainfall events, the risk of flooding increases in many regions of the world.
Therefore, finding effective and sustainable ways to manage flood risk is a pressing challenge for society.
One possible solution is to use natural flood management (NFM) techniques, which involve mimicking or enhancing natural processes to store and slow down water in the landscape.
NFM can reduce the peak flow and volume of water reaching downstream areas, where flooding is most likely to occur.
It can also provide multiple co-benefits, such as improving water quality, biodiversity, carbon sequestration, and recreation.
One of the most promising NFM techniques is to install beaver-like dams in rivers and streams. These are human-made structures that resemble the dams built by beavers, which are semi-aquatic rodents that are known for their engineering skills.
Beaver-like dams are made of natural materials, such as logs, branches, leaves, and mud, and are designed to allow some water to pass through or over them.
By creating these dams, we can harness the benefits of beavers without introducing them to the environment, which may have some negative impacts on existing ecosystems.
How beaver-like dams work
FRANCOIS NASCIMBENI/AFP via Getty Images
Beaver-like dams work by creating temporary water storage areas upstream of the dam, which can reduce the downstream water level and flow during a storm.
The dams also divert some water to the surrounding floodplain, where it can infiltrate into the soil or evaporate into the air. This reduces the amount of water that reaches the main channel and contributes to flooding.
The effectiveness of beaver-like dams depends on several factors, such as the size, shape, location, and number of dams; the characteristics of the river and its catchment; and the type and intensity of rainfall.
To optimize the performance of beaver-like dams, it is important to monitor their impacts on water levels and flows over time and adjust them accordingly.
Several studies have shown that beaver-like dams can reduce flood risk and provide other benefits for people and nature.
A recent study by Cardiff University and the University of Worcester assessed the impact of 105 leaky barriers on a small river in Shropshire over a period of two years.
The study found that the barriers could store enough water to fill at least four Olympic-sized swimming pools during significant weather events, such as Storm Dennis in 2020.
The barriers raised water levels up to 0.8 metres at each barrier, which slowed down the river flow during these storm events and protected communities downstream from flooding.
Another study reported that beaver-like dams can enhance habitat diversity for river insects and animals, trap pollutants, and enhance the supply of sediment to the floodplain.
They also added resilience to the river during spells of dry and hot weather by preventing it from drying up entirely.
A report by PreventionWeb highlighted that beaver-like dams can also provide social and economic benefits, such as creating opportunities for education, recreation, tourism, and employment.
They can also reduce the costs of conventional flood defenses, such as concrete walls and embankments.
