عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Investment on soil and water conservation measures require detailed study and planning based on documented experiences and evaluation impacts and benefits of measures. Introducing success of measures needs evaluation of soil and water conservation projects by a standard and uniqe method by all experts in different regions of the country. In this research, mechanical measures of soil and water conservation in the form of rock-cemented dams were evaluated in the Nasim-abad watershed with semi-humid climate and mean annul precipitation between 500 and 700 in the northwest of Shiraz using global WOCAT( World Overview Conservation Approaches and Technologies) program. Evaluation in different aspects such as social, economic, physical and human environment before and after of applied technologies carried out. Results of this research revealed that surface runoff was increased due to over grazing and rangeland change to poor drylands. Increased surface runoff caused gully erosion on natural thalwegs. Rock-cemented dams with one meter height and a total volume of 34496 cm3 were applied to control gully erosion. Although gully headcut are retreating upslope, sediment due to gully erosion was deposited behind established dams and completely filled tham. Constructed dams were not established by watershed residents and they did not gain the knowledge of dam construction and the benefits of using them. Therefore, it can be said that the participation of land users was negligible in the phase of dams establishment. Also, the results of research indicated that benefit/cost ratio was about 0.1 that means this sort of project was not justifiable in view point of economy. As this technology could not mitigate gully development, there is not positive effects for dams unless sediment trapping. After filling dams, sediments flow over and reach to downstream rivers and Salman-e-farsi dam. Analysis of physical, ecological and economical impacts of dams construction indicated that this technology has positive feedback in view point of sediment trapping but it is not recommendable in view point of economic, ecologic and maintenance.