A water bar
or interceptor dyke
is a road construction feature that is used to prevent erosion
on sloping roads, cleared paths through woodland (for utility companies such as electricity pylons), or other accessways by reducing flow length. It is a diagonal channel across the road surface that diverts surface water that would otherwise flow down the whole length of the road, gaining velocity, off the road and into a stable drainway. By constructing a series of water bars at intervals along a road, the volume of erosive water flowing down the road is reduced. Without waterbars, flooding
, and accelerated road degradation can occur.
The drainway carries the water that would otherwise be carried by the road. Thus for proper operation of the water bars it must be stable and regularly inspected to ensure that it is free of silt buildup or other obstructions.
Waterbars are usually constructed at an angle across the road. They tend to make passage by vehicle on the road difficult; usually a large high-clearance four wheel drive vehicle is required. Waterbars are common on roads such as Forest Service Roads, especially in mountainous terrain where lots of rainfall occurs.