Remote sensing and GIS based multi-criteria analysis approach with application of AHP and FAHP for structures suitability of rainwater harvesting structures in Lai Nullah, Rawalpindi, Pakistan

Rapid urbanization in the twin city of Rawalpindi and Islamabad led to increase in deforestation due to built-up infrastructure, hence; an increase in flood peaks in catchment area of Lai Nullah. For this purpose, rainwater harvesting is a viable and sustainable approach for surface water management. In this study, an integrated approach of Remote Sensing and GIS was applied by using multi -Criteria Analysis based Analytical Hierarchy Process (AHP) and Fuzzy Analytical Hierarchy Process (FAHP) for determination of the Rainwater harvesting (RWH) potential zones. For MCA, five bio-physical criteria were selected including rainfall, slope, drainage density, Land Use Land Cover (LULC) and soil texture. These spatial results of FAHP potential sites map in comparison to the AHP potential sites map of RWH shows a 4% increase in the proportion of good potential zone, as well as, similar decrease of 4% in the moderate zone were observed. According to the classified classes the excellent and good classes together covered a range of 56-62% in both the RWH potential sites maps. Suitability maps of check dams and percolation tanks were deduced separately by assigning the mean influence weights of AHP and FAHP with allocation of rank value (1-5) to the respective distributed zones of considered bio-physical parameters as per IMSD guidelines in the weighted overlay The overall final suitability maps with 40 sites of percolation tanks and 12 sites of check dams were identified. Sensitivity analysis revealed that rainfall and drainage density show enhanced criticality to the RWH potential sites. Validation of suitable sites was carried out through ground truth data of LULC, stream order map, AHP and FAHP potential sites maps. Final suitability maps shows that the RWH structures are situated in the good and excellent zones of AHP and FAHP potential sites map, and lies on the 2nd and 3rd stream order. It is observed that the suitability index is very high in agricultural and forested areas which are accordance with IMSD standards. The present study findings determined suitability maps may be used as prospective approach by watershed managers, planners, and decision makers for the watershed management of Lai Nullah catchment area.