caspian sea level fluctuation and determination of setback line

in the past 25 years, rising of the caspian sea level, part of a natural treat to the sea, has inundated and destroyed many buildings and arable lands and threatened many inhabitations in coastal areas. the main reason for these damages is that the law-setback has lost its efficiency and human activities have proceeded seaward. the goal of this study is to introduce a proper setback line for the southern coast of caspian sea on the basis of critical water elevation and the results of coastal vulnerability assessment to sea level rise. this setback contains vertical and horizontal buffers. the coastal vulnerability index (cvi) method is used for coastal vulnerability assessment and is also used in the geographic information system. five variables in two sub-indices were used in this method. the final map obtained from coastal vulnerability assessment divided the coastal zone into low, moderate, high and very high risk categories based on quartile ranges and visual inspection of data. a mean distance of very high risk category of vulnerability map from a second vertical buffer in each rural district was then proposed as a width of horizontal buffer in the same rural district.