At bridges where removal is difficult or expensive, accumulations are likely to remain in place longer. For example, at State Route 59 on the Eel River near Clay City, Indiana, at State Route 59 on the Vermilion River near Cayuga, Indiana, and at Sneed Road on the Harpeth River of Tennessee, accumulated drift accessible from the banks had been removed at the time of the visit, while drift in the center of the channel remained in place . The presence of drift accumulations from previous floods can have several consequences. A pier with accumulated drift on it may shed additional drift less effectively than if it were bare. An accumulation developing on top of a previous accumulation grows more rapidly through interaction with the drift below it.
Drift remaining on the bridge has the potential to promote the growth of an island or bar.
The use of long spans allows the bridge designer to place fewer piers in the water, and makes it easier to avoid placing piers in the path of drift or near the center of the channel, where access is most difficult. Long spans, especially those longer than the design log length, are less likely to be blocked by drift. Because of these advantages, the use of long spans should decrease the frequency and difficulty of drift removal. Wall piers that extend upstream to the edge of the parapet are easier to clear than piers of other types. Drift trapped on trusses and piers with multiple columns can be entangled among multiple structural elements.