MODELING FLOOD HAZARDS IN NORTHERN MINDANAO, PHILIPPINES USING HEC-RAS AND LIDAR-DERIVED DEM

摘要

The progress of high resolution flood hazard mapping become the mainstream in the academic exercise worldwide. In the Philippines, high resolutions maps have evolved to aid in flood-related disaster management and monitoring. High resolution maps become useful for localized emergency response such as evacuation and rescue operations during the disaster. However, high resolution flood maps in Northern Mindanao, Philippines are not readily available. This study aimed at modeling and mapping flood hazards within the six rivers in Misamis Oriental of Northern Mindanao, Philippines namely; Alubijid, Balatucan, Cabulig, Gingoog, Linugos, and Musimusi rivers. The study applied Geographic Information System (GIS) and the family of Hydrologic Engineering Center (HEC) model of US Army Corps such as Hydrologic Modeling System (HMS) and River Analysis System (RAS) with the integration of Light Detection and Ranging (LiDAR)-derived Digital Elevation Model (DEM). Hydrologic and hydraulic models were generated using HEC-HMS and HEC-RAS modeling tools. The developed hydrologic models were calibrated using the hydrologic data of the different typhoons hitting the respective river basins. Applicability of the calibrated models were evaluated using quantitative statistical measures such as R~2, RSR, NSE, and PBIAS. River flow hydraulics were performed through unsteady flow analysis using the hydraulic model reconstructing the events and simulating the several known return periods using Rainfall Intensity Duration Frequency (RIDF) data. Results revealed that the simulated flood depth were close to the actual event occurrences indicating applicability of both developed HEC-HMS and HEC-RAS models for all the river basins. Result of the study is significant for effective and efficient disaster risk reduction management especially during localized response operations. Moreover, the study is helpful for a more informed and a science-based decision especially in crafting policy recommendations on disaster awareness, mitigation and control measures through proper land use zoning and urban planning.