WEPP:Road Batch road surface
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N -- Native surface
G -- Gravel surface
P -- Paved surface
A native surface road is a road constructed from the material
occurring on the site, with no added surface material.
Unless native surface roads are regularly maintained or have little
traffic, they will likely be rutted, and the rutted option should be
selected.
A gravel surface road assumes that gravel has been added to the
surface.
The greatest benefit of adding gravel is that the road design can be
maintained in spite of traffic, so that insloped and outsloped unrutted
designs can be selected with confidence.
Under heavy traffic, a gravel road may also become rutted, and regular
maintenance or reduced tire pressure on heavy vehicles are some methods
that can help to maintain the desired design.
A paved 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 most of the sediment from the road prism is deposited in the
buffer.