Assessment of the Existing Drainage System in Infanta, Quezon Province for Flood Hazard Management using Analytical Hierarchy Process

The residents of Infanta, Quezon Province has been dealing with flood and calamities for several years. With that, this research focused on the radical assessment of existing drainage system in the municipality. Lidar DEM was used to determine the elevation and slopes in the area which is a very important input drainage system analysis. The researchers did vulnerability assessment in the area considering relevant factors about the existing drainage system. These factors were elevation, population, soil permeability, rainfall intensity, flow discharge of drainage, distance from river basin to drainage line, and land cover. The importance of each factor was determined based on the survey made from the researchers of the FRAMER project of Mapua-DOST PCIEERD. Weights of each factor were identified with the aid of Analytical Hierarchy Process. Weights of each factors are as follows Flow discharge capacity with 22.3%, Elevation 17.1%, Soil permeability 14.6%, Distance to river 14.5%, Rainfall intensity 12.4%, Population 11.8% and Land Use 7.2%. Validity of the survey made from the experts were checked by calculating the consistency of their answers. Consistency index was calculated to be 0.11 which is in the range of acceptable value. A risk map was then created using geographical information system to determine spatially which drainage line is most vulnerable to flooding. It was found out that there are seven zones that are at risk to flooding due to the inadequacy of the drainage and other factors mentioned in the vulnerability assessment but Poblacion area is the one that needed the rehabilitation the most.