Environmental Engineering Reference
In-Depth Information
As
F
increases from values well below 1, small sand bed ripples are transformed to larger
dunes out of phase with surface ripples. These are planed off where
F
approaches 1 and
antidunes form where
F
is more than 1, this time in phase with surface waves (Figure
14.11).
Channels are clearly dynamic landforms making constant adjustments between form
and function, to which we return below. Continuing questions about the way in which
water flows, and carries out work, focus appropriately on very small channel segments or
controlled laboratory flumes. For the purpose of
Figure 14.11
Relations between bed forms in sandy alluvial
channels, channel roughness and stream flow. Compare with
Figure 12.13.
Source: After Selby (1993).
summarizing general impacts on the land surface and fluvial landsystems, we need to
appreciate the potential energy available in each channel segment and the shear stress
mobilized at the channel boundary.
Stream power
, measured in W m
−2
, is defined as:
and
boundary shear stress
, τ
o
, is defined as:
