Jeremy Venditti

A river runs through his lab

October 2, 2008

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SFU geographer Jeremy Venditti will use a recently constructed flume—a simulated river channel that is 15 metres long by a metre wide and 60 cm deep, in the new Environmental Fluid and Sediment Dynamics Lab—to learn more about the relationship between river beds and river flows, and the role of flow resistance in creating conditions for flooding.

"River channels are the result of a series of sedimentary processes that happen when turbulent flow interacts with sediment particles," says Venditti, who has spent the past several years studying the characteristics of the Fraser River from Mission to Steveston.

"How a river channel behaves is governed by the amount of water delivered, the amount and calibre of sediment delivered, and the resistance to flow presented by the channel.

"Of all of these, the resistance to flow, which is strongly influenced by how the bed is formed, is the most poorly understood."

The problem, Venditti says, is an increasing reliance on computer models to predict how rivers respond to climate change and sedimentation associated with land-use practices and human activities. "Our inability to estimate flow resistance reliably is a major problem. Attempts to develop a flow model for the Fraser through the Lower Mainland to estimate impacts has been hampered by a lack of understanding of flow resistance, resulting in errors in water levels.

"Ultimately, during floods, water levels control what areas will be inundated—so the need to develop a physical understanding of flow resistance is critical."

The flume will allow Venditti and his research group to conduct experiments using a range of velocities and depths needed to build a true physically based understanding of a river bed’s topography. These experiments are critical to attaining a full understanding of the morphodynamics of the Fraser River and other sand-bedded rivers.
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