Flood Susceptibility and Conceptual Drainage Simulation of Barangay Calaba, San Isidro, Nueva Ecija Using HEC-RAS 2D
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Flooding is one of the most common natural hazards in the Philippines, especially in low-lying areas where heavy rainfall, flat terrain, and poor drainage cause water accumulation. Barangay Calaba in San Isidro, Nueva Ecija frequently experiences flooding during intense rainfall, yet localized assessments of flood-prone areas remain limited. This study aims to assess rainfall-induced flooding in Barangay Calaba using two-dimensional hydrodynamic simulation and to examine the possible effects of a conceptual drainage system on flood conditions. A quantitative case study approach was applied using the Hydrologic Engineering Center’s River Analysis System (HEC-RAS) 2D. Terrain data from the ALOS PALSAR Digital Elevation Model (12.5 m resolution) and rainfall data from PAGASA’s Rainfall Intensity Duration Frequency analysis were used to simulate flooding under two scenarios: existing conditions without drainage and conditions with a conceptual drainage system. Simulation outputs were analyzed to identify flood-prone areas and estimate flood depth and inundation extent, while results were compared with the available Project NOAH flood dataset for validation. The study provides insights into localized flood behavior and the possible influence of drainage improvements on flood conditions and supporting local flood mitigation planning
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