Temperature Effects in High-Transport, Flat-Bed Flows

Flume experiments show that in flows over flat beds of fine sand, the concentration of suspended load near the bed and the bed-load discharge of different size fractions of the bed sediment react differently to a change in water temperature. For example, an increase in water temperature alone caused the concentration near the bed and the bed-load discharge to increase for the finer fractions of the sediment and to decrease for the coarser fractions. The reaction of bed-load discharge of sediment of a given size to changes in water temperature can be expressed in terms of the boundary Reynolds number, R∗_b, which is formed of the product of shear velocity and sediment diameter divided by the kinematic viscosity of the water. An increase in temperature will cause an increase in bed-load discharge of a particular size fraction when R∗_b based on the mean size of the fraction is less than 13, and a decrease in bed-load discharge when R∗_b exceeds 20.