Prioritization of Appropriate Sub-basins in order to Forest Harvesting using HEC-HMS Model (Case Study: Kheyrud Forest)

Forest cover is one of the most effective factors in reducing flooding in northern Iran، so that in recent years the destruction، land use changing and uncontrolled harvesting of forest areas، has greatly increased the number and magnitude of floods. So far، there have been few studies on forest hydrology in Iran، particularly the northern Hyrcanian forests. This study examines the impact of a hypothetical harvesting operation، on the basin output hydrograph، will provide the opportunity to study the prioritization of forest basin for harvesting operations. SCS method and rainfall - runoff HEC-HMS model were used to simulate the design flood return periods of 2، 5، 10، 25، 50 and 100 years. The results showed that the A1 and A2 sub-basin have maximum peak flow at the outlet that ranked in the first place of flooding. So that، the implementation of harvesting scenarios in these sub-basin، the f and F% indices values have been increased intensively ​​than other sub-basins، Although، it was similar trend between harvesting operation increasing and increasing f parameters in A1 and A2 sub-basins. But considering the area، greatly increases of the hydrological response to the harvesting operation was occurred in the A1 sub-basin. Results for positioning suitable areas for harvesting operations، also showed that the priority order of B3، A4، B2، A3، B1، A2، and finally A1 sub-basins. With implementation of the harvesting operation scenarios over 21 percent، in the most sub-basins، the amount of peak flow and flood volume have been increased greatly.