Hydrological and Hydraulic Analyses for a Proposed Bridge in Floridablanca, Pampanga

Abstract

Several studies prove that hydraulic factors play a major part in bridge deterioration. Thus, the conduct of hydrological and hydraulic analyses are essential in ensuring the safety, stability, and long-term performance of bridge structures, particularly in flood-prone river systems. The study evaluated the hydrological conditions of a proposed bridge crossing the Porac River between Barangays Poblacion and Valdez in Floridablanca, Pampanga. Watershed characteristics were analyzed by topographic survey and Digital Elevation Model based watershed delineation using HEC-HMS. The Rainfall Intensity-Duration-Frequency of the Philippine Atmospheric, Geophysical and Astronomical Services Administration was used to perform the Rainfall frequency analysis with the 50-year rainfall. Peak design discharge obtained by rainfall-runoff simulation is 662.60 cu.m./s which is used as input for hydraulic modeling on HEC-RAS. The catchment area of watershed is 120.46 sq. km., longest flow path is 37.99 km and average basin slope is 8.26%. Hydraulic analysis showed a critical flow depth of 24.71 m for the design flood condition. The minimum bridge span of 23 meters was determined from the Design Guidelines, Criteria and Standards, and the proposed bridge will be able to span between existing riverbank slope protection structures. The hydrologic and hydraulic models combined showed that the proposed bridge size is sufficient to safely pass the design flood, and is a prudent, cost-effective, and resilient solution for the site. The findings of the study underscore the importance of a comprehensive hydrological and hydraulic evaluation in the development of sustainable and flood-resilient bridge infrastructure.