Prospects of changes in the channel system. Widespread timber harvesting in the basin. History or prospect of marked changes in basin land use. Channel system fully stabilized, and unlikely to undergo significant change. Indirect evidence of drift transport If indirect evidence suggests that the rate of drift generation is high, or could become high, the potential delivery of drift will be controlled by the ability of the stream to transport it.
Most streams are capable of transporting some drift.
Assume that a given stream can transport drift unless evidence shows that drift accumulates where it is generated, rather than being transported downstream. Channel dimensions upstream from the site, particularly channel width, affect the size of drift that can be transported, and thereby influence the potential size of accumulations. The width and depth of the channel upstream from the site may increase over the life of the bridge. Indicators of potential increases should be taken into account when estimating future dimensions. Erosion-resistant bed and bank material may limit future channel evolution, and effective channel stabilization may prevent future widening and deepening.