Fauna-friendly culverts

Frogs, turtles, snakes, trouts and salmons among others are blocked by the culverts that lay beneath our roadways.

The importance of a good drainage is known since the work done by the Scottish engineer Mac Adam in the dawn of 19th century. Surface drainage would have to be completed by ditches and culverts as a mean of driving the drained water away from the road and into the streams that existed before.

Traditionally, culverts have been installed with consideration for their hydraulic capacity. The cross-sectional flow area is smaller than that of the stream approaching it and the velocity of the water entering the culvert is greater than that of the natural stream. However, culverts that are correctly designed and installed (see figures) do not hinder animal passage.

Upper pic: George Washington National Forest.
Lower pic: British Columbia Min. of Transp.