May
05
2010

Developing a virtual stream to help restore real ones

With forty-four percent of our 3.5 million miles of rivers and streams degraded due to sedimentation and excess nutrients, stream restoration has become big business in the United States. Estimates show that over $1 billion has been spent on stream restoration projects in the U.S. in every year since 1990.

Trouble is, the field of stream restoration lacks a lot of scientific rigor, making the prediction of successful restoration strategies difficult. Take, for example, one of the most commonly used tools of the trade—the in-stream structure. Man-made, in-stream structures (think small wall jutting out into the water from a stream bank) are frequently used in stream restoration and management to try to stabilize beds and banks or to improve aquatic habitat. Despite the frequency with which they are used however, engineering standards for the design and installation of the structures are inadequate, a problem that would be good to remedy if we are to make reliable predictions about whether a given stream restoration strategy or project will succeed.

Establishing comprehensive, quantitative engineering guidelines for in-stream structure installation and maintenance is far from simple though. The underlying physical processes that govern the behavior of a stream and its inhabitants are very complex. To deal with the complexity, researchers at the National Center for Earth-surface Dynamics (NCED) have come up with a novel approach—build a near-field scale experimental stream and a computational “virtual” stream to help elucidate the underlying interactions of water, sediment, and biota.

The experimental stream is the Outdoor Stream Lab (OSL) that sits right on the Mississippi River. The virtual stream is the (surprise, surprise) “Virtual StreamLab” (VSL) that exits as code within massively parallel supercomputers. This past summer, NCED researchers were able to complete their first simulation of a real stream (the OSL) using the VSL (see the video above). The simulation involved mapping more than 90 million data points into the computer model. The result was the most accurate model of a real stream to date.

The ability to simulate water flow over topography with this degree of realism will provide researchers with the insights necessary to improve sustainable stream restoration strategies and help to optimize techniques to fight erosion, prevent flooding, and restore aquatic habitats. NCED researchers are currently using their simulation to develop comprehensive, quantitative design, installation, and maintenance standards for in-stream structures.

With so many miles of degraded streams and rivers in the United States, the VSL is a good step in the right direction for the design and use of in-stream structures specifically, and for the field of stream restoration generally.

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