Majid Kazemzadeh; Zahra Nouri; Majid Rahmani; Asghar Bayat; Salma Saedi Farkoush
Volume 32, Issue 2 , July 2025, , Pages 124-139
Abstract
Background and objective: In recent years, extensive watershed management measures including biological, mechanical and biomechanical measures have been carried out with the aim of flood, erosion and sediment control and water storage in the different sections of research, study and implementation ...
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Background and objective: In recent years, extensive watershed management measures including biological, mechanical and biomechanical measures have been carried out with the aim of flood, erosion and sediment control and water storage in the different sections of research, study and implementation in the country. Evaluation of watershed management plans in order to analyze the performance of implemented watershed management measures and develop basic solutions is one of the basic needs in watershed management. Therefore, the aim of this research is to quantitatively and qualitatively evaluate the effects of biological and biomechanical measures of watershed management on the vegetation cover changes in Azimieh watershed, Karaj, Alborz province.Materials and methodsIn this study, vegetation changes were determined using Landsat series 5, 7 and 8, satellite images, and NDVI index in a period of 20 years (2000-2019). Then, by using the polytrend model, the trend of linear and non-linear changes and the effect of water management measures implemented in the watershed on the vegetation cover in the Azimieh Karaj watershed, Alborz province, were investigated. Also, in order to evaluate the accuracy of the results and satellite images, field measurements were also used. Also, in order to investigate the effect of climatic factors on vegetation changes, drought index and rainfall data of Karaj station were used.ResultsResults of trend showed that 41.9% of changes were significant over 20 years. 88.3% of the significant changes in vegetation were increasing. The results of Polytrend method showed that the changes in vegetation were cubic, linear and quadratic with values of 63.4%, 27.8% and 8.8%, respectively. Evaluation of the effects of implemented measures to improving the vegetation status of the watershed showed that the percentage of canopy in the watershed was on average 28% before implementing the watershed management measures, which has increased to 34% after the implementation of watershed management measures. Of the total area of biological operations in Azimiyeh watershed (2724 hectares), in 70% of the area, changes in the vegetation status of the rangeland have been nonlinear and these changes were in projects such as seeding and tree planting and terrace. Also, the vegetation in a parts of the downstream areas of Azimiyeh watershed have been destroyed by non-linear trends due to the growth and development of residential areas and civil works such as the construction of Hemmat Highway.ConclusionThe performance evaluation of watershed management projects in Azimieh Karaj watershed showed that watershed management measures have caused a significant increase in vegetation in the region. On the other hand, development and urbanization in the downstream areas of the watershed has caused the loss and destruction of vegetation over the past years. The evaluation of watershed management plans can show the positive and negative results of the measures implemented over the years, and in this way, steps can be taken to solve their obstacles and problems.