Direct measurements of secondary currents at a river inflexion point
SECONDARY currents are defined as currents which occur in a plane normal to the local axis of primary flow. They may develop in pipes or open channels as a result of non-equal distribution of boundary shear stress or by skewing of cross-stream vorticity into a long stream direction1–3. Secondary currents distort the distributions of primary isovels and boundary shear stress from those found in simple flows and have important effects on sedimentary processes of erosion and deposition4,5. Direct measurements of secondary currents in river bends were reported recently6. Further data have been obtained for the reach around the inflexion point between bends (Fig. 1) and are reported here.
Discussion of “on the origin of River Meanders”
In developing his formulas the author assumes that meandering is initiated by forced oscillations and he postulates some cause which will bring about the forced oscillations; for example, a tributary confluence, a sand bar, or the like. So it appears that if the forced oscillations are in fact the cause of meandering, they are not the prime cause but rather the result of some other cause or causes. In his conclusions the author states rather cautiously that his formulas do not take into account the entry conditions. However, early in the paper he states that the first serpentine bend provides the disturbance for the next bend and so on. There is no doubt that this is so, but surely it contradicts the statement about the entry conditions, since the first bend can be regarded as the entry to the second, the second for the third, and so on.
Resistance Properties of Sediment-Laden Streams
Experiments were made to determine the relative effects on the friction factor of a flow of the suspended sediment load and the configurations which form on sand beds of streams. Results showed that the friction factor of a 
stream carrying suspended sediment is less than a comparable one without sediment. They also showed that the reduction of friction factor due to changes in bed configuration is much larger than that due to suspended sediment.