Land use changes and restraining environmental risks via mitigation approach, the case of Darakeh-Velenjak watershed in Iran

Widespread land use changes and unusual uses of highlands in Northern Tehran (Darakeh-Velenjak Watershed) have markedly caused to pose environmental risks and unsustainability. This research aims to study land use changes in Darakeh-Velenjak Watershed, to identify the key risks which can be posed by land use changes, and to present appropriate strategies using mitigation approach. To study land uses changes, satellite images were used (TM 1987, ETM+ 2000, and IRS 2018) and assessed by concentrating on four classes of land including vegetation, arid, roads and built-up areas. To extract the necessary information from the satellite images, Supervised Maximum Likelihood Classification algorithm was used, further complemented by visual interpretation methods. The sample population for conducting the Delphi technique consisted of 34 experts. The results of this research exhibited that from 1987 to 2018, vegetation had dramatically decreased, while arid, roads and built-up areas had increased. The results also revealed that in 1987, around 37.3% of the study area was covered with vegetation while in 2018, less than 14.54% of the area was covered with vegetation. In contrast, built-up, roads and arid areas which respectively covered 8.96%, 1.75%, and 51.99%, increased to 15.18%, 3.19% and 67.08% in 2018. In addition, the results of this study illustrated that key risks of land use changes in the Darakeh-Velenjak Watershed could be divided into natural and human risks. The human risks with an average score of 4.21 were more than natural risks. Finally, strategies have been presented using mitigation approach in the study area. Results revealed that avoidance strategies with an average score of 3.37 were situated in the first rank because unfortunately this watershed has been damaged by excessive land use changes in an aspect of developing buildings, roads, tourism infrastructures and etc.