Comparative Application of Gray Clustering Analysis (GCA) and Analytical Hierarchy Process (AHP) Approaches for Identification of Appropriate areas of Flood Spreading (Case Study: Garbaygan Watershed)

The first and most important step in any floodwater-spreading project is the identification of the most appropriate areas for water infiltration into the aquifers. For this purpose، conjunctive use of Geographical Information System (GIS) and Multi-Criteria Decision Making (MCDM) may lead to more accurate results. In this study، the study area is Garbaygan Watershed located in the Fars province، Iran. Then، parameters affecting the site selection of floodwater spreading projects were defined and appropriately classified. To enhance the accuracy of the study output، Gray Clustering Analysis (GCA) and Analytical Hierarchy Process (AHP) approaches were considered. In the GCA، the data have grey membership functions and in contrast to fuzzy systems، they have defined limits. Grey membership functions aim to enhance the quality and weight of data by valuation of information layers. The GCA and AHP approaches were applied using this data set and the final maps of the watershed based on each model were prepared in different suitability classes. The results of both models showed that quaternary formations including Qscg، Qgsc، Qb، Mm-1، Qc2 and PLQb have the suitable condition for floodwater spreading. Also، upper parts of alluvial fans، pedimonts and sparse rangelands have acceptable conditions for such projects based on geomorphologic and land use characteristics. Meanwhile، the results showed the GCA outperformed in site selection compared to the AHP approach.