evaluation of watershed plan on the rate of erosion and sediment in kan basin

in iran due to the lack of long experience in the implementation of soil conservation and watershed management plans, these measures have not been evaluated quantitatively and specific methods for this purpose have not been provided. in this research effort is to investigate the effect of watershed management operations performed in can basin in 1379, on the amount of erosion and sedimentation and rate of project success or failure and its causes. so after providing the required information and statistics and being sure about the authenticity and accuracy of statistics and statistical reconstruction of defects with conventional methods, to investigate the effect of implemented projects on erosion and sedimentation rates, average of suspended sediments in the period before project implementation (1986-2000) and in the period after project implementation (2001-2008) was calculated using sediment rating curves through intermediate technique class, and using daily water discharge, watershed erosion and deposition were also calculated using mpsiac model. specific erosion and deposition map was provided in the period after project implementation using arc gis software and finally the amount of efficiency and effect of this operation on the amount of erosion and deposition rates was judged. the results of studies showed that due to operating this plan, the average amount of suspended sediment has changed from 47892 tons per year during the statistical period before the plan to 22365 tons per year during the eight-year statistical period after it. the amount of erosion and sedimentation has shifted from 66758 tons to 50549 tons, which shows the positive effect of plan on reducing the amount of suspended sediment and the lack of effective role in reducing the rate of erosion. the main reasons for the low efficiency of watershed management plan implemented in relation to decreasing the amount of erosion are: lack of suitable biological operations in the basin (less than 25 percent of the volume of the proposed action), focusing on mechanical operations, weaknesses in project monitoring and evaluation during all stages of its implementation, failure to observe the standards and technical points such as non-conforming structures built between locations and proposed locations, lack of standards in building the necessary structures and inappropriate dimensions of structures, destruction of floor section in mortar stone structures and etc.