Modify Existing Forest Road Network and Offer New Path with Least Variation

Abstract

In this study we tried to modify the existent road network with minimal changes in its terms. Therefore Map of the existent road, hydrology,
slope, direction, fault lines, pedology, geology, roads and waterways crossing and the drainage were prepared and digitized, then these maps
analyzed by Arc GIS 9.3. We used Pegger accessory package of ArcView 3.2 software in order to employ step compass technique and road design
using longitudinal slope direction and negative points. Therefore, 8 variants (proposed road) in the study area was designed using Pegger software.
Five of eight variants were selected, and then combined with the existent road. We selected the common paths with existent road, and then reforms
were undertaking by removing some parts of the existence road because of passing from negative points and replacing some paths of this variants.
After preparing the improved road network map, outdoor observation were taken to verify the accuracy of the implemented reforms, For this, we
surveyed the longitudinal slope, drainage conditions and passing positive and negative points of substitute paths (5 variants) by field controlling.
The existent road network survey results showed that the network percent equal to %51, %42 of existent roads were on slopes over %60 and %16.5
were completely on unstable points, 5 lateral drainage with incorrectly situation and 750 meters of the road is located along the north-west’s fault
line. The results of modified path with minimal changes indicate that the road situation decreased from %42 to %22.6 by passing some hillside with
slope over %60, from 47 to 44 points by road crossing with existent waterways network and from 750 meter to 0 (no passing) by road crossing the
fault lines.