Flood for Hazard Assessment of Gandara River: Input to Flood Control Program

The flooding problem in San Jorge Samar may be solved through an effective implementation of flood control program. As such, the primary purpose of this study is to estimate the potential parameters of flood occurrence of the Gandara River along San Jorge channel through its topography, hydrological characteristics and siltation manifestation. As part of an assessment process, this study also defines the existing practice of flood control initiatives, evaluate and eventually propose a flood control program. As guided by the DPWH Flood Control Planning Manual, assessment and computation of the needed parameters in planning and design of flood control program was processed through HEC-HMS (Hydrological Engineering Center–Hydrologic Modeling System) software. Findings suggest San Jorge urban areas, as well as portions of its adjacent barangays as depicted in topography, is surrounded by significant upland and rolling area. Gandara River Basin at San Jorge channel is considered a flood prone. As to some hydrological characteristics contributory to a flooding event, at extreme precipitation, the resulting floodplain adjacent to the river channel covers a total 4,315,568 square meters, inundating big portion of mostly a commercial, educational and agricultural area. Peak discharge is 1474 cubic meters per second, that produces a flood depth that reached up to about 7 meters which are significantly high. Sedimentation or siltation is also contributory to flooding events in the area, As there is no concrete strategy of flood control yet, flooding event remains a devastating phenomenon annually. Hence, it is imperative to establish a mitigating if not a control measures for Gandara River at San Jorge, Samar, Philippines. Presented in the last part of this study is a proposal for Flood Control Program for Gandara River as a recommendation to the local government of San Jorge, Samar, Philippines.