Open check dams tame savage eddies and stop sediment flow.Wild water streams can now be captured in mathematical models. Experiments, or waiting for a downpour, are no longer needed.

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Mud streams rushing down through narrow valleys cause ravages. A good enough reason to stop them, for example, with dams. But the problem with taming the wild water streams is the varying amount of water. In summer, hardly any water comes down the mountains; whereas in spring, the water streams swell to savage eddies. An open check dam provides the solution: it stops tidal waves, but lets small amounts of water through.

Marcela Busnelli, an Argentinean PhD student in Civil Engineering’s fluid mechanics department, investigated how to determine the effects of an open check dam without having to first carry out experiments.

Busnelli drew up a mathematical model that also described the water discharge of wild mountain streams. She applied this model to dams with small gaps. Busnelli: ”Fast running water contains a lot of sediment, which will not settle until the flow velocity decreases. When the water discharge is high, a reservoir is formed behind the dam. The entering mountain stream loses velocity quickly and it’s sediment will settle. The water leaving the reservoir by passing the dam, will thus contain less sediment.” The savage eddy has been tamed. In case of low discharge of the mountain stream, no lake is reservoir is formed and the water just runs through the gap in the dike.

A few of these open check dams have already been built in the Alps. Their designs were based on experiments and experiences with earlier dams, not on calculations. ”A few years ago, such a dam was built in Italy. Since then, it hasn’t rained very hard, so we still don’t know if it functions,” says Busnelli. With her model, she can determine the dam’s effects easier, quicker and cheaper. Moreover, simulations can be done which aren’t possible in a laboratory.

The model calculates the solution for a number of equilibrium equations, and if needed, three-dimensional. ”With a three-dimensional model you can do the same things as with a

one-dimensional one; it only takes the computer more calculation time,” remarks the Argentinean. The decrease in flow velocity of water discharging into a reservoir is a

one-dimensional problem. ”For modelling the water flow through the dam, you need a two-dimensional model, because the water also moves vertically.” If the width also changes, for example, the gap when the dike breaches, a three dimensional model is needed.

Busnelli was raised in the mountains. By applying her model to mountain streams and to dikes giving way, she neatly combined her interests and the Dutch situation.

Open check dams tame savage eddies and stop sediment flow.

**Wild water streams can now be captured in mathematical models. Experiments, or waiting for a downpour, are no longer needed.**

Mud streams rushing down through narrow valleys cause ravages. A good enough reason to stop them, for example, with dams. But the problem with taming the wild water streams is the varying amount of water. In summer, hardly any water comes down the mountains; whereas in spring, the water streams swell to savage eddies. An open check dam provides the solution: it stops tidal waves, but lets small amounts of water through.

Marcela Busnelli, an Argentinean PhD student in Civil Engineering’s fluid mechanics department, investigated how to determine the effects of an open check dam without having to first carry out experiments.

Busnelli drew up a mathematical model that also described the water discharge of wild mountain streams. She applied this model to dams with small gaps. Busnelli: ”Fast running water contains a lot of sediment, which will not settle until the flow velocity decreases. When the water discharge is high, a reservoir is formed behind the dam. The entering mountain stream loses velocity quickly and it’s sediment will settle. The water leaving the reservoir by passing the dam, will thus contain less sediment.” The savage eddy has been tamed. In case of low discharge of the mountain stream, no lake is reservoir is formed and the water just runs through the gap in the dike.

A few of these open check dams have already been built in the Alps. Their designs were based on experiments and experiences with earlier dams, not on calculations. ”A few years ago, such a dam was built in Italy. Since then, it hasn’t rained very hard, so we still don’t know if it functions,” says Busnelli. With her model, she can determine the dam’s effects easier, quicker and cheaper. Moreover, simulations can be done which aren’t possible in a laboratory.

The model calculates the solution for a number of equilibrium equations, and if needed, three-dimensional. ”With a three-dimensional model you can do the same things as with a

one-dimensional one; it only takes the computer more calculation time,” remarks the Argentinean. The decrease in flow velocity of water discharging into a reservoir is a

one-dimensional problem. ”For modelling the water flow through the dam, you need a two-dimensional model, because the water also moves vertically.” If the width also changes, for example, the gap when the dike breaches, a three dimensional model is needed.

Busnelli was raised in the mountains. By applying her model to mountain streams and to dikes giving way, she neatly combined her interests and the Dutch situation.

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