Coupled Hydrologic-Hydraulic Modeling-Based Flood Inundation Mapping for a Segment of the Tullahan River in Valenzuela City, Philippines

Anthropogenic activities brought about by accelerated urban expansion trigger changes in the hydrologic response of watersheds. The Philippines, being prone to the occurrence of extreme weather events and urban development, has experienced more frequent and more devastating floods that have caused damage to life and property throughout the years. Thus, the need for modern approaches to disaster risk and preparedness is essential to lessen the extent of damage that flood events bring to communities. This study was conducted to exhibit the capability of using a coupled hydrologic and hydraulic model to produce a flood inundation map for a segment of the Tullahan River in Valenzuela City, Philippines. A hydrology model was set up and calibrated using the Hydraulic Engineering Center Hydrologic Modeling System (HEC-HMS), and simulations show that the peak discharge for the 10-year and 100-year return periods ranges from 11.88 cubic meters per second (cms) up to 23.48 cms. Based on the produced flood inundation map using Hydrologic Engineering Center-River Analysis System (HEC-RAS), the maximum flood depths reach up to 2.91 m, and the inundated area covered 0.9419 km2 for a storm with a 100-year return period which occurred close to the banks of the river at mid-stream. The findings of this study could help local planners in promoting the use of modern tools, such as computer models, in disaster-risk preparedness toward resilient communities.