Flood Hazard Assessment of Gandara River, Philippines

Abstract

The flooding problem in San Jorge Samar, the Philippines can be effectively addressed using a holistic approach using factual information. This is the main purpose of the study, which is to understand the parameters contributory to the flood hazard specifically along the San Jorge channel of the Gandara River. The paper also evaluated flood control initiatives implemented by authorities. The evaluation is 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 rurban areas, as well as portions of its adjacent barangays as depicted in topography, is surrounded by significant upland and rolling hills. San Jorge basin is considered a flood prone. Using the designed rain based on historical data, it was found out that the flood plain which is 431 hectares (which includes a big portion of mostly commercial, educational and agricultural area) adjacent to the river channel will be inundated; A. Peak discharge is 1,474 cubic meters per second, resulting in a flood depth up to about 7 meters is expected. This can go higher if sedimentation or siltation is not managed. There is no concrete strategy to control flood hazard. There is an immediate need to establish measures to prevent a catastrophe when the San Jorge channel of Gandara River in Samar capacity is exceeded.