A new method of sediment‐transportation

Abstract

The writer has observed in two streams a method of transportation of solids in suspension which he has not seen described in any literature, and which may therefore present a method of the transportation of sediment which is new to this science.The observations were made in the Canadian River near Tulsa, Oklahoma, and in the Root River in southeastern Minnesota. In both of these streams the water was flowing on a bed of clean sand and was clear, so that the phenomena could be observed. The sand‐bed was in the form of ripples, which consisted of a series of small bars scattered irregularly over the bed of the stream with relatively flat upstream slope and steep downstream slope. In the Canadian River the action occurred over a large area of the stream‐bed , but in the Root River it acted only at a single point. The phenomena consisted of an upward‐moving turbulent current which started from a point on the downstream‐sloping face of the ripple and carried the bed‐material upward. This turbulent current extended to the surface, where it spread out and mixed with the horizontal current of the stream and the sediment carried up with it spread out with the current and gradually settled back to the bottom. These upward currents did not move from place to place, but remained stationary, always rising from the end of the same ripple. It has been suggested by A. A. KALINSKE that they are caused by the wake formed behind a sand‐ripple on the bed, since they resemble the wake formed behind a ship rather than a vortex. Perhaps this method of sediment‐transport should be called “ripple‐wake suspension”.