Document Type : Research Paper
Professor, Soil Conservation and Watershed Management Research Institute, AREEO, Tehran, Iran
Assistant Professor of Soil Conservation and Watershed Management Department, Zanjan Agricultural and Natural Resources Research Center, AREEO, Zanjan, Iran.
Awareness of erosion and its spatial changes is a guide for managers and planners in the important matter of water and soil protection in watersheds. In the present study water flow and sediment data of 40 hydrometric stations in the Middle Alborz region and in the statistical period between the water years 1980-1981 to 2020-2021 were used. First, the most important factors include 30 hydrological, physiographic, geomorphological, geological and soil characteristics climate land use and vegetation as independent variables and two sediment characteristics. The most important characteristics of effective basins in sedimentation were identified. In the next stage, the study area basins are divided into six homogeneous groups based on selected characteristics and cluster analysis and using multivariate regression by stepwise method to model between specific sedimentation and basin characteristics. According to the selected regression models, it is determined that the amount of special sediment in the Middle Alborz region to five factors of agricultural land area (rainfed, irrigated and orchards), the area of sub-basins, the total area of erosion-sensitive and Quaternary structures, The average annual discharge and the form factor of the basin depend on the fact that these five factors control 92% of the sediment production changes in the selected sub-basins. Then, considering the sediment transfer coefficient of the sub-basins, the amount of soil erosion was determined and the soil erosion map was drawn for the Middle Alborz region. The results showed that the average sedimentation rate and the average weight of soil erosion in the study area were 3.84 and 13.56 tons per hectare per year, respectively. In general, the factors affecting erosion and sedimentation of the Middle Alborz region can be divided into three groups: land use change due to human activities, geology and physiography.