Until a few years ago at a bridge location on the Beaverdam Branch of the Juniata River in Blair County, Pennsylvania, repeated removal of stream sediment and debris by Pennsylvania Department of Transportation (PennDOT) maintenance crews was routine. Each time, the activity disturbed aquatic species habitat at the site. In just four days and using only one piece of equipment, PennDOT fixed the problem. The solution: a "W" rock vane 20 meters upstream of the bridge and an inverted U-shaped "cross vane" 20 meters downstream. Like the vanes of a windmill, which divert air flow, the rock vanes divert water flow (and collected sediment) away from the stream bank and toward the center of the river. The devices effectively narrow the stream channel to replicate upstream and downstream natural channel widths, resulting in higher velocities which flush away any accumulated bedload material and minimize streambank erosion. And the rock vanes have created deep resting and hiding pools for the river's brown trout, rock bass, central stoneroller, creek chub, cutlips minnow, white sucker, and other aquatic species.
--Aug 21, 2006
|The W-shaped rock vein resists the accumulation of sediment around the bridge pilings and minimizes disruption of aquatic habitat.|