Cross Drainage Design of Forest Road in Shafarood Basin,Guitan Province

Forest road network is one of the most important forest management projects, that plays a great role in .timber transportation as well as other forest services such as tourism, hunting, etc; Essentially water accumulation on forest roads can be the main reason for road destruction through .erosion and decrease ' of road strength. Generally forest roads are constructed in humid and rainy zones where water is one of the most important factors in their erosion, therefore drainage is important for decreasing the
..destructive effects.
The results in this research indicate that, drainage pipe diameter in talwegs could be estimated by considering discharge in talwegs, rain intensity, runoff coefficient, area and hydrological conditions. Pipe diameter for conducting road canal water is determined on the basis of canal bed susceptibility to surface erosion, canal cross section and dischagre. Road location on the foothill, slope length, and water discharge play the main role in determining the distance between pipes, the more the height of road, the more will be the distance between pipes.