The potential for a river to deliver drift combines the potential for wood to be introduced into the channel and the potential for drift to be transported downstream to the bridge site. Information gathered to aid in the assessment of drift may bear on potential for drift generation, drift transport, or both.
Some information is direct information about large woody debris and drift.
Other information about the stream and its basin has implications for drift generation and transport. 10K GIF version of this diagram Figure 28 . Flow chart for evaluating potential for drift delivery. Direct Evidence from Observed Drift Observations of drift provide the most direct evidence for assessing potential for drift delivery to a site. Observations of drift may come from bridges or from other sites of accumulation, and from the channel system upstream from the site or from channel systems in similar basins.