Forest Skid Roads Planning using Geographic Information System (GIS) and Analytic hierarchy process (AHP): (Case Study: Darabkola forest)

Skid trails are considered as a completion of wood transport network and are closely related to the condition of road network, silviculture practices, logging methods, topography, slope, soil mechanical capabilities and other factors. The purpose of this study was to design skid trails in parcels No. 22 and 23 in Darabkola forest using GIS with AHP in order to cross paths on sustainable areas and a convenient access to the forest area. For this purpose, maps of slope, inventory per hectare, stream density, inaccessible areas (outcrop and regeneration), pedology, aspect, geology, forest type, and altitude, which are important factors in designing of skid road network, were used as layers of information and Evaluation of designed skid trails. The results of AHP showed that slope with a relative weight of 0.301 and altitude a relative weight of 0.029 had the most and least effects on designing of skid road network; the acceptable incompatibility was 0.08 in this case. Finally, two variants were designed for the study area. The first variant had a length of 2957.51 m and a density of 25.06 m/ha; the second variant had a length of 3853.85 m and a density of 32.66 m/ha. The situation of variants passes through different areas showed that 83.54% and 84.81% of the length of the skid trail was passed from very proper and proper areas in the first and second variants, respectively; 16.46% and 15.27% was passed from poor and very poor areas in the first and second variants, respectively. Compare designed variants using the nearest route showed that the average distance of each node to the track for the first variant was 64.77 meter and for the second variant was 45.56 meter. The results of this study showed that by considering the skidding distance of 140 m and with a maximum longitudinal slope of skid trail (% upward and -35% downward) the second variant was preferred due to the more passing percentage (84.81) on proper and very proper areas and lesser passing percentage (15.2) on poor and very poor areas and a cover percentage of 48.47% than the first variant with a passing percentage of 83.54% on proper and very proper areas and 16.46% on poor and very poor areas and a cover percentage of 32.18%. The evaluation results of the nearest path showed that the second variant had the best distribution because the average distance between each node to its path was lower.