The use of subjective–objective weights in GIS-based multi-criteria decision analysis for flood hazard assessment: a case study in Mazandaran, Iran

Abstract

The assessment of flooding areas and developing flood hazard maps play a key role in prevention of the many social, economic and environmental damages caused by flood. Most parts of Mazandaran, Iran are at risk of flooding caused by heavy rainfall and rivers. In this paper, the flood hazard map of Mazandaran province is assessed using subjective and subjective–objective weights in an Ordered Weighted Averaging-based GIS analysis. Flood hazard maps are produced based on the two types of weights, along the scale ranging from the pessimistic to optimistic decision strategies. The accuracy of the flood hazard maps was evaluated based on: (1) the percentage of historic flood occurrences that are within the flood hazard maps and (2) the assessment ratio, which is the ratio of known flood areas to whole area in a particular class of flood hazard maps. The results indicate that the percentage of flood areas produced by subjective and subjective–objective weights in “Very high class” are the same in the cases of most pessimistic (14.65%) and optimistic strategy (100%). However, in other strategies (0 < ORness < 1), the subjective–objective weights show better values than subjective weights for percentage of flood hazard areas. Similarly, the assessment ratio results show that flood hazard areas produced by subjective and subjective–objective weights in “Very high class” are the same in the most pessimistic (4.47) and optimistic strategies (1.2).