Experimental and Numerical Modeling of a Tide Embankment Section Subjected to Storm Surge in Tacloban City, Philippines

Abstract

Following the devastating Typhoon Haiyan, a project initiated by the Philippine government, known as Road Heightening and Tide Embankment (RHTE), was constructed to protect the coastal communities of the Leyte region in the Philippines against future storm surges. This research focuses on this newly built structure, which was investigated for coastal flooding and wave overtopping against extreme waves. Experimental and numerical modeling were conducted to simulate wave-structure interaction under different water level conditions. A 1∶30 scale representative geometry of the tide embankment was set up inside a wave flume containing a scaled beach profile representing areas beyond the No-Build Zone mandated by the government. Dam-break wave flow was used to generate turbulent bores similar to that of a storm surge. For the numerical model, SolidWorks and ANSYS CFX version 17.1 software were used. The multiphase Volume of Fluid (VOF) method was used to track the free surface of the fluid flow and was shown to be an accurate tool for numerical validation, as the maximum wave height distributions in the presence of the structure using both methods were in close agreement with one another, but the numerical results overestimated the wave heights. The final design of the tide embankment with a return wall was modeled using ANSYS CFX. Experimental and numerical models generated wave heights that were higher than Typhoon Haiyan with inundation heights of 6 to 9 m above mean sea level (MSL) approaching the structure while the inland wave height was approximately 2 to 4 m above MSL. Results of the experiment also showed that the presence of the structure reduced the water level by 1 to 5 cm (about 0.3 to 1.5 m in actual scale). Moreover, the presence of a return wall will reduce the inland inundation height between 0.1 and 0.5 m above MSL.