Waterbar

Most waterbar spacing, however, is in the magnitude of 80 - 120 feet.

Source: wiktionary

With waterbar placement every 20 feet, in addition to mulching, the expected erosion would be less than 1 ton per acre, well within the tolerance level.

Source: wiktionary

The angle at which the waterbar lies across a trail is important. Too close to the perpendicular, and silt will build up behind the waterbar; too small an angle will cause the trail to wash out.

Source: wiktionary

A valve type of waterbar therefore is maintained in the stressed condition caused by shrinkage of the concrete during setting.

Source: wiktionary