Flume Studies of the Transport of Pebbles and Cobbles on a Sand Bed

Abstract

During experi ments on sf:d mcnt trnn.sport and real tanca to now with a un.Uorm o. 33 m.r.a sand, data w r t aken on Ute movement ot indh'i• dual rocks having lntermodiato diameters from about O. t to o. 5 foot. Th experiments were conducted in flumo z-toot wide by 60-foet long and for most runs, depth. WM held constant at o. 5 f'eet. The exp r:l menta showed t at rocks on U1e &and bed inov d down tren consistently only it the flow wa.s la the uppor regimci that la, only if 1be ed formi, were plmio boo, standii\i w :vcs , or snUdunes. The rocka moved at velocities th.at ere appro.dmately one • halt or tho averase ve-loc1ty Q.f the water. With all bed form3 in the low<?r flow regime (ripples, ripples .superimposed upon dt111&s, and dw1\?), the ro-eks always moved upstream and down into the bed. That ts, tho rocks moved Into a scour pocket thu formed at the upstream de ot th rock. The moyem.~nt upatream d down into thG bed b limit ed by nnd :ipproxim tely equal to the di to.nee below tho origin. al rock po ition or the rninumum b~d elevaUon plus approximately one-hall the rock diarnet r. Th data ind1cat<t that er • • bedded sand depoait• for~d y t ripple or dun phaaoa of tran port would conudn few, U any, pebbl es or cobbles. B~aua• tb now, in at leut the downstream rettc • or P"J()9t riven 14 lD thct lower regim.c, the upgtreaxn movement and acour into tho bed demonstrated la thu• experimenta is an lmportant factor 111 the aorttag prooeaa.

The transport of gravel in an ephemeral sandbed river

“…This conclusion contradicts results from flume experiments (e.g. Fahnestock and Haushild, 1962) which indicated that the particles move during the upper regime only.…”

“…Flume experiments (e.g. Fahnestock and Haushild, 1962;Simons and Senturk, 1992) showed that gravels on sandbed rivers are likely to be embedded and buried by advancing sediment. Here the relation between burial depth and particle size was examined using available data and reported on the basis of the overall seasonal distributions.…”

“…Therefore, the maximum size of the sediment does not necessarily represent the maximum transporting power of floods (McKee et al, 1967). Fahnestock and Haushild (1962) conducted the first reported flume experiment on the movement of gravel on sand. Downstream displacement of individual stones occurred only during the upper plane bed, standing wave or antidune regimes.…”

Distribution and sources of obsidian in the Rio Grande gravels of New Mexico

“…Finally, experimental studies indicate that movement of pebbles and cobbles in sand-bed rivers occurs mainly in the upper reaches where high-velocity flow during flood stage is sufficient to initiate movement. Downstream reaches of sand-bed rivers thus contain fewer pebbles and cobbles (Fahnestock and Haushild, 1962).…”

Unrestrained Cylinders Rolling in Steady Uniform Flows

“…An interesting investigation of the movement of round (almost spherical) rocks in stream flows was found (Fahnestock and Haushild, 1962). Though it lacked details and had limited application to the present problem, it may provide useful information for future investigations of cylinder motion on a sand bed.…”