Evaluating the Impact of Watershed Management Activities on Upstream Urban Areas (Case study: Tehran 5th and 22nd District Upper Watersheds)

      One of the problems of some cities in the country, especially those in the vicinity of mountainous watersheds, is the containment and control of runoff, erosion and sedimentation that results in many damages to downstream facilities and infrastructure each year. Watershed operations have been proposed for years to reduce and mitigate destructive effects, and some measures have been taken in these areas. But evaluating such projects can play an important role in determining the effectiveness and future planning of natural resource management and execution plans. In this regard, in order to show the impact of this operation, two urban watersheds of District 5 (Koohsar) and District 22 of Tehran, which consist of a number of sub-basins, were selected, in which only biological operations (vegetation cover) and integrated operations (biological and structural), respectively implemented. Then, using the MPSIAC empirical model, the impact of operations performed in these basins was quantitatively calculated to reduce the internal factors of the model and its final output, erosion and sediment yield, in the two periods before and after the project implementation. The results show that in the first watersheds, biological operations including planting and vegetation development have a 45% impact on improving the natural environment of their urban watershed with reduced degradation, and in the second watersheds, a combination of structural and biological operations reduces the rate of erosion and sediment production by 55%. The results show the positive role of watershed management practices and the effectiveness of integrated methods in reducing the problems caused by upstream catchments overlooking cities and also shows how to deal with watershed activities in cities upper watersheds, is slightly different from the classical watershed management methods and should be considered with a different approach.