WEPP:Road Road Surface

Paving a road greatly decreases road surface erosion, but increases the runoff. Increased runoff from the road surface can cause increased erosion on fillslopes, ditches, and flow paths leading from the road to the forest. Sediment eroded on the fillslopes is more likely to be transported to streams with the increased runoff from a paved road.

Paved roads show the best benefit on outsloped roads, or roads with armored ditches with minimal buffers. They are least beneficial on scenarios with insloped roads, or roads a moderate distance from the stream. On roads a long way from the stream, it makes little difference what the road treatment is, as all of the runoff is absorbed by the forest, and hence the sediment from the road prism is deposited.