Mapping and analysis of flood scenarios using numerical models and GIS techniques

Flooding in the Philippines is becoming more hazardous over the years intensified by climate change, poor drainage and expanding agricultural industries. In managing this natural disaster, flood hazard maps serve as a significant tool to local government in enabling them for adequate disaster response and planning. Through flood simulation and mapping using numerical models and GIS techniques, this study aimed to determine the amount of flood exposed building features and agricultural resources to different flood scenarios in the floodplain of Sawaga watershed. The Hydrologic Engineering Center’s, hydrologic modeling system and river analysis system of the US Army Corps were the models used for the flood simulation. Feature datasets utilized for flood exposure analysis were derived from Light Detection and Ranging data and satellite images. Results revealed that of the 12 flood-prone barangays in Sawaga floodplain, four (Managok, Santo Niño, Simaya, and Violeta) are most exposed to flood hazards when it comes to the count of affected building features and area of flood-exposed agricultural cultivations. Residential buildings associated as the local community are the most exposed to flood hazard accounting 94% of the total affected building features for all flood scenarios. Moreover, rice plantation is the most exposed agricultural land use to the flood hazard constituting 66%, 74% and 77% of the total flooded agricultural cultivation in the floodplain by the 5-year, 25-year, and 100-year return period scenarios, respectively. The generated maps and extracted information will serve as viable tools to guide disaster managers in the city in executing informed decisions in facing the onslaught of flood disasters.