GIS-Based Flood Hazard Mapping in Gingoog River, Mindanao

Abstract

Flooding is one of the most devastating natural disasters in the Philippines, especially in Mindanao. This study aimed to generate datasets of flooding along the Gingoog River based on Geographic Information System (GIS). The method employed simulation and mapping of flood hazards using the Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) and the HEC-River Analysis System (HEC-RAS) within the GIS environment. Rainfall data on December 15, 2015, with a total amount of 20.8 mm and peak discharge of 43.49 m3s-1, were used to simulate flood hazards. The model was calibrated, and its accuracy was tested, and after which, its overall evaluation showed a satisfactory performance, implying applicability to simulate floods during extreme rainfall events. Using Light Detection and Ranging (LiDAR) data, flood maps of the three return periods were generated within HEC-RAS. Results showed that flooding extended up to 2.965 km2, 4.165 km2, and 5.040 km2 with maximum flood depths of 7.77 m, 8.12 m, and 8.49 m for 5-year, 25-year, and 100-year return periods, respectively. The model, together with the hydrologic behavior of the watershed such as the extent of flooding, is very helpful for the development and enhancement of early warning systems in the affected areas.