Stepped-bed morphology in arid gravelly channels

The stepping phenomenon indicates systematic channel-bed variations that are not identical to the well-known pools and riffles. Channel beds in the Dead Sea area demonstrate that the main elements in a stepped bed are the regular and the rapid segments, which constitute distinct populations. The bed material of the stepped channel is heterogeneous in size, but significant uniformity prevails within the segment types. The cyclic spacing of the segment types deviates clearly from that of pools and riffles in that it is at closer intervals. The coarser the sediment, the more pronounced the segmentation. Stepping may produce variations in flow velocities from subcritical to supercritical and causes the overall flow regime to vary. Widening and braiding of the channels downstream does not replace the steps. Megasteps form in the canyons but are not cyclic. Conditions favoring stepping indicate a coarse fluviatile environment.