In 2016, Washington installed 26 human-made beaver dams in a damaged creek; after one flood, sediment rose nearly 5 feet, and water depth increased 11%

In eastern Washington, a damaged creek received an unusual form of help in 2016. Instead of rebuilding the channel with conventional engineering structures, restoration workers installed 26 human-made structures designed to behave like beaver dams. Within months, the experiment was reshaping the stream, slowing water and allowing sediment to accumulate where erosion had previously deepened the channel.According to the Washington State Department of Ecology, the structures were installed along about 1,900 feet of Myers Creek as part of the Triple Creek restoration project. The creek had been badly altered by a major rain-on-snow event in the 1990s, which sent unusually large flows through the channel, deepened it and left steep banks while draining parts of the surrounding wetlands. When the beaver ponds that had once helped hold the floodplain in place disappeared, the drier ground also became more favourable to invasive plants. The restoration team therefore turned to what are known as Beaver Dam Analogues, or BDAs. They were intended to recreate some of the physical effects of natural beaver dams and, importantly, encourage beavers to return and eventually maintain the system themselves.Building a dam without the beaversThe structures at Myers Creek were simple. Wooden stakes measuring 3 to 6 inches in diameter were driven into the streambed, and branches were woven between them. Some structures were built across the streambed to slow the flow and retain sediment. Other structures served as deflection structures where the flow would be diverted towards the sides of the streambed, encouraging the channel to meander. The goal is not simply to create a series of ponds. Sediments could be retained through reducing the power of flowing water in the stream. The channel rose and reconnected with its natural floodplain.The Washington Department of Ecology also notes that the restoration team planted native vegetation and tackled reed canarygrass, an invasive plant that had become widespread after the creek became drier. The project included 14 planting sites and protection for other plants to help regenerate a riparian plant community that could restore shade, stability and food sources for returning beavers. However, there is one crucial difference between a natural beaver dam and a BDA. Unlike a natural beaver dam, a BDA cannot repair itself.According to research published in River Research and Applications, both natural beaver dams and beaver dam analogues can alter stream-channel conditions by slowing water, retaining sediment and influencing channel shape. The study found that these structures could promote sediment accumulation and modify local channel geomorphology, although their performance could vary during high-flow events. At Myers Creek, the 26 structures also interacted with the spring 2017 floodwaters, helping redirect flows, widen the incised channel and encourage sediment deposition instead of allowing the water to keep cutting through the channel.The results were significant. Sediment from the streambanks and upstream area built up by as much as 5 feet in some places, raising the streambed close to the historical floodplain. An annual survey in the first year after the high-flow events also found that water levels were more than 11% higher. The experiment thus revealed an important characteristic of such a restoration technique. The dams did not need to stay as solid structures to achieve the desired effect. Their interaction with water, sediment, and streambanks caused changes in the creek’s morphology.The beavers eventually returnedPerhaps the most notable result was what happened next, without any further action from the crew. Beavers came back to the area just days after construction started in 2016, despite their absence from the area for almost twenty years. At first, this created an unforeseen challenge because the beavers ate willow branches used in the habitat, so the crew switched to conifers and red-osier dogwood.By 2017, the beavers were doing more than just colonising the restored section. These beavers had constructed a dam at a site where weaving was not completed and had also contributed to the construction of another BDA. The beavers had even constructed a pioneer dam below the last structure installed. This was close to the project’s goal: using man-made structures to restore a degraded stream and encourage beavers and plant life to return.Triple Creek does not prove that man-made dams can fix every impaired water system. Their efficiency is determined by the state of the stream channel, availability of sediment material, plant cover, and water regime, as well as their maintenance. But Triple Creek suggests that, in a creek that has become too deep, fast and disconnected from its floodplain, mimicking beaver activity can help.You use AI every day. Now get your AI Quotient. Take the AIQ test.