By using a model of a meandering stream, scientists have shown two ingredients that are very important for stream health: vegetation to reinforce banks and prevent erosion, and sand to build point bars and block off cut-off channels and chutes. This knowledge will help stream restoration efforts in the future.
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Image Courtesy of Zina Deretsky/National Science Foundation
Living, Meandering River Constructed
News story originally written on September 28, 2009
Scientists have built a scale model of a living, meandering river in a lab. From the model they have learned a few things: the importance of vegetation to reinforce the river banks and the importance of sand in healthy river life. The first finding isn't a surprise because scientists have known for a long time that vegetation slows erosion on river banks. But this is the first time sand has been seen as being important for meandering rivers. They learned that sand helps build point bars and blocks off channels and chutes, which keeps new streams from forming and taking away water flow from the river.
The model includes gravel (to represent sand), fine sediment, vegetation and water. It's the first time a model of a river has behaved like a real river that is 50 to 100 times the size of the model. It takes 130 hours for the model to erode its river banks and build point bars by depositing model sand and gravel. This process is the same as what would happen to parts of the Mississippi River would over five or seven years.
Meandering streams are healthy because they contain shallow portions and deeper pools of water. These different habitats mean that different species can live there. Scientists hope they can use what they learn from this model to restore other streams back to being healthy, meandering streams.
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