Hydrologic Modeling and Delineation of Calumpang River Watershed using GIS and Hydrologic Model System

The Calumpang Bridge in CALABARZON Region, Southern Luzon Philippines did not withstand the river current brought by Super Typhoon Glenda (Rammasun) on July 2014, causing the destruction of one-third of the bridge, thus resulting to traffic congestion and economic distress for the residents and businessmen. This paper aims to create a calibrated hydrological model. Specifically, it focuses on delineating watershed, simulation based on observed flow data and validation that will be the basis for flood risk map for the river. The watershed has been delineated and it is calibrated, the basin was modeled using Hydrologic Model System and GIS Applications to determine hydrologic parameters which have spatial characteristic and to compute the peak Discharge and loss infiltration. The model delineated by the use of GIS software has been hydrologically corrected. The model describes the correlation of the rainfall, losses, time of concentration, Storage factor and amount of discharge. It shows that the amount of Rainfall at a given time dictates the amount of discharge the watershed generates. The higher the rainfall amount, the higher the discharge. The model was validated using Percentage Error and Rational Method, and due to the accuracy of the validated model, it provides a promising approach to Bridge Structural Design and Flood Risk Map Generation.