Parsakhoo Aidin, PhD.

The fine-textured soil in forest road ditches is very susceptible to water erosion especially in rainy seasons in Hyrcanian forest. This study examined the yield of ditch segment-scale sediment after releasing two flow rates of 5 l s-1 and 10 l s-1 in segments treated by riprap (RR), grass cover by Festuca arundinacea L. (GC), compacted cotton geotextile (CG) and wooden wattle by local slash (WW). Sediment sampling from the runoff was carried out at the end of each segment every minute. Runoff flow velocity in different treatments was measured using an electromagnetic flow meter. Sediment concentration and runoff velocity in treatments of RR, GC, CG, WW was significantly lower than that of the control plot (Ctl). Increasing flow rate from 5 l s-1 to 10 l s-1 caused no significant change in sediment concentration (except for Ctl and RR) and runoff velocity (except for Ctl and CG), which means that some water might have penetrated into treated soil by RR, GC and WW and this is not acceptable in forest road maintenance practices. Sediment yield from RR (0.36 g l-1) and Ctl (0.50 g l-1) under the flow rate of 10 l s-1 was significantly higher than that of 5 l s-1 with values of 0.21 g l-1 and 0.38 g l-1, respectively. Minimum amount of sediment concentration was observed for CG (0.20 g l-1) with compacted ditch bed. Moreover, runoff velocity in CG and Ctl under the flow rate of 10 l s-1 was significantly higher than that of 5 l s-1. For a forest road with dimension 30×50 cm, slope of 5%, and clay soil with porosity of 57%, treatments of compacted CG can be used in ditch with low flow rates (5 l s-1) and high flow rate (10 l s-1) because of their high efficiency in reducing sediment yield.

Dust is often generated from the dry surfaces of unpaved forest roads as a result of vehicular traffic. Dust particles can negatively affect vegetative growth, water quality and road traffic quality. In this study, some environmental friendly anti-dust agents including sugar cane molasses, polyacrylamide (PAM) and bentonite were used to control dust emission from the road surface under three different concentrations within the 3, 9, 27 and 81 day timeframe. Rear-mounted spray system and dustometer devices were used for implementation of treatments and dust emission recording, respectively. Leaf samples were collected from trees adjacent to road to measure the dust deposited on the leaves by centrifuging dust solution. The results showed that molasses achieved higher efficiencies in term of dust reduction and cost effectiveness than those of PAM and bentonite in Loveh forest, where high levels of fines are present in the road surface materials. 2% and 4% PAM were the most efficient dosages in terms of dust control and cost effectiveness in Shastkalateh and Kouhmian forests, respectively. It was detected that in all sites most of the dust emitted from the road surface was deposited on the leaves of Carpinus betulus L. and Alnus subcordata L., while smooth surface of the leaves retained lower amount of dust in Parrotia persica CAM. It is concluded that the amount of fine aggregates in surfacing materials, type and dosage of anti-dust agent play an important role in the effectiveness and longevity of treatment.

This study was done to determine the appropriate maintenance strategies for the deteriorating gravel forest roads in the Mediterranean, sub-humid and semi-arid climates. Unmanned Aerial Vehicle (UAV) was used to monitor Unpaved Road Condition Index (UPCI), immediately after maintenance activities and seasonally in one year. The deterioration time of the wearing course was predicted using Markov chain analysis. Results showed that roads in sub-humid climates presented lower UPCI (7.19) compared to the Mediterranean (7.81) and semi-arid (8.82) climates. When roads were maintained by a high-budget strategy, deterioration time was longer than when other strategies were used. The cost-effectiveness (CE) value of the low-budget strategy was more favorable than different strategies in all traffic levels of the Mediterranean climate and high-traffic roads in a semi-arid environment. Low-budget maintenance activities include one culvert improvement per 6 km, light blading, and 30 mm layer graveling. In a semi-arid climate, a medium-budget maintenance strategy was more efficient in medium and low-traffic roads. Medium, high, and low-budget maintenance strategies were efficient in high, medium, and low-traffic roads in sub-humid climates. High-budget maintenance activities include one culvert improvement per 4 km, heavy blading and local compaction, and 60 mm layer graveling. Overall, it was concluded that monitoring UPCI over time and probability analysis using time series is helpful for a sustainable and long-term management of forest roads.