'Star Trek-like' expedition provides deeper insight into Fraser River

Rafting scientists recently carried out a "Star Trek-like" expedition that provided a deeper insight into the world of Fraser River.

Scientists at Simon Fraser University studied river flow in bedrock canyons for the first time have discovered that previous conceptions of flow and incision in bedrock-rivers are wrong.

The researchers put their lives into the experienced hands of Fraser River Rafting Expeditions, which took them into 42 bedrock canyons. Equipped with acoustic Doppler current profilers to measure velocity fields, they rafted 486 kilometres of the Fraser River from Quesnel to Chilliwack. Their raft navigated turbulent waters normally only accessed by thrill-seeking river rafters.

Jeremy Venditti, SFU geography professor, said that for the first time, they used oceanographicp; instruments, commonly used to measure three-dimensional river flow velocity in low land rivers, to examine flow through steep bedrock canyons and the 3-D instruments captured downstream, cross-stream and vertical flow velocity.

Colin Rennie, an Ottawa U civil engineering professor, said that they observed a complicated flow field in which high velocity flow plunges down the bottom of the canyon forming a velocity inversion and then rises along the canyon walls.

This has important implications for canyon erosion because the plunging flow patterns result in greater flow force applied to the bed, he further added.

River flow velocity in bedrock canyons also influences the delivery of sediment from mountain-rivers to lowland rivers.

The study is published in the journal Nature.