Downstream changes in the channel geometry of a large gravel bed river

摘要: [1] Field data obtained on a nearly contiguous segment of the Colorado River in western and eastern Utah are used to examine mechanisms driving downstream changes channel geometry. Measurements characterizing bank-full hydraulic geometry, bed material grain size, average gradient were made at closely spaced intervals 10 alluvial quasi-alluvial reaches covering 260 km river. These indicate that surface subsurface sizes small relation change slope: over full length study area, median size sediment decreases by factor little more than 2, whereas slope about 5. The offset large increase depth relative width, such Shields stress, τ*b, is constant downstream. For reach as whole, τ*b averages 0.049, which roughly 50% higher threshold for load transport.