Assessing the Accuracy of GIS-Based Analytical Hierarchy Process for Watershed Prioritization; Gorganrood River Basin, Iran

Abstract

Watershed prioritization based on the natural and anthropogenic factors involves by locating the critical areas of flood hazard, which cause socio-economic and environmental consequences to take up mitigation activities on priority basis. The pair-wise comparisons of natural and anthropogenic factors is a bit problematic, because these two mentioned factors are different from typology view point. In order to assess flood hazard potential by using (1) only natural factors (FHPNF), (2) only anthropogenic factors (FHPAF), and (3) ensemble the obtained sub-watersheds priorities from natural and anthropogenic factors , the coupling of the Analytical Hierarchy Process (AHP) and Geographical Information Systems (GIS) were applied the Gorganrood river basin of Iran. Each effective factor was assigned to appropriate weight based on Saaty’s 9 point scale and the obtained weights were normalized through the Eigenvector method. By using the Weighted Linear Combination (WLC), two flood hazard potential indexes were defined separately for anthropogenic and natural factors. Finally, both indices values were combined to determine sub-watersheds priority. For the validation of the predictions, the Receiver Operating Characteristic (ROC) curve and historical data of flash flood events were used. According to the results of ROC curves, the FHPNF and FHPAF maps showed a reasonable good performance in watershed prioritization with area under ROC curve (AUC) values of 76.1 and 79.5 %, respectively. In addition, these results imply that one and two sub-watersheds fall under very high and high priority, respectively. The results of this study act as guidelines for managers and planners to determine sub-watersheds priority and rational management of watersheds based on both natural and anthropogenic components.