(...Changing Scale in Environmental Impact Assessment(case studies:Sefid Roud Dam,Iran and Haizuka Dam

Deciding a proper scale for Environmental Impact Assessment (EIA) is crucial, and a function of several parameters such as budgeting, location of study area, types of impacts, map resolution, and data availability. Scale can be categorized into three dimensions namely temporal, mass, and spatial scales. However, in each dimension of scale, the exact expression of the scale refers to the theories that might be examined. Therefore, in the EIA studies that are referred to changing scales of mass or spatial information in the study unit(s), the outcomes of the EIA report might be influenced by changing scales. Thus, the question is "to what extent the findings of an EIA report can be influenced by changing their scales"? Developing the idea, 10 study units were delineated in a sub watershed in Japan. Then, via applying zooming (changing the resolution of a map) and panning (moving the framework on a map) within degradation modeling for an EIA it was cleared that how changing spatial scales can influence the results of the EIA. For example, those areas with high degradation number in high resolution maps were classified as low degraded areas in low resolutions maps, while the exact location was unchanged. Improving the impacts of changing mass scale in an EIA, another different in size dam in Iran was selected to compare the influence of mass change on the EIA. Then, an ad hoc scaled-weighted matrix was developed for two dams. It is cleared that the evaluation of changing mass-scale can be conducted more quantitatively than changing spatial scales, due to possibility of mass impact-factor delineation via water weight of the reservoir. Changing scale can also be divided into two different levels that are project and planning levels. In a project, the EIA assessors are dealing with temporal, mass, or spatial effects of data accuracy, but in planning level the approach focuses on different landscapes, types of planning, or different strategies.