WEPP:Road predicts the annual average erosion from insloped or outsloped forest roads and predicts the amount of sediment that will leave the buffer.
Roads are a chronic source of sediment from forests, producing some amount of erosion every year they are in use. When a road is built, the soil is deliberately compacted for greater ease of vehicle travel; this compaction also reduces water infiltration and increases runoff. The amount of traffic is a factor in road erosion. More traffic leads to greater compaction while at the same time generating loose sediment on the surface that can wash off when it rains.
Without active management, most dirt roads develop wheel ruts over time. The ruts collect water, which then runs down the road in a concentrated flow path - just like running a garden hose on bare soil. The longer the path, the more runoff is collected, and the more soil is dislodged. If the road erodes too much, it becomes unusable and difficult to repair. Most sediment comes from just a few places on the road network. By identifying these areas, mitigation efforts can be concentrated, thus reducing the erosion rate of the road network overall.
Because of the ability of forest roads to generate sediment, it is important to know in general terms how much soil is coming from a particular segment. This is where the online tool WEPP:Road comes in. This model focuses on the road characteristics that have the greatest effect on sediment delivery. These characteristics can easily be determined by the user. Managers using this tool typically begin with a combination of field surveys, mapping, and GIS tools to estimate the road segment length and gradient, road width, surface conditions (i.e., rutted), road ditch condition (bare or vegetated) and traffic volume. This information is entered into the WEPP:Road interface, for either a single road or in batch mode (hundreds of road segments). The output is an estimate of the average annual sediment delivery of a road or road network.
Average annual sediment delivery