Assessment of drainage system and factors influencing the forest road destruction

Preservation, restoration and development of natural resources makes the necessity of forest roads construction undeniable; however, their potential impacts approve the importance of standard compliance and also continuous maintenance of forest roads. The aim of the study was to evaluate the standards of forest road and drainage of the district 4 of Shenrood basin in Guilan province in the northern Iran. For this purpose, the road side slope, longitudinal slope, distance between culverts, and diameters of culverts, depth, big and small base of culvert. 7250 m of the existing roads as a representative of the existing road were surveyed. Result of one sample t-test showed that the variables of side slope (with mean value of 2.9%) and also ditch depth (with mean value of 0.34 m) were not significantly different from the standard values; however, the other factors indicated a significant difference with the standards (P>0.05). The most failure types were the rut (39%) and the least was rocky protrusions (8.7%). Results showed that the number of existing culverts were not sufficient and therefore could not conduct volume of water (P>0.05). The intervals of the installed culverts was 234 m which is inappropriate based on the standards.