Manila Bay is a shallow coastal water encompassing the urban areas of Metro Manila and variouscities of sub-urban provinces in the Philippines. It is a relatively shallow semi-enclosed basinwith an average depth of 20 m whose coastal areas are crowded with residential, industrial,agricultural, and aquaculture production. Its shallow depths imply that the effect of wind stress onsea level becomes appreciable in driving storm surges even during enhanced Southwest Monsoonand the passage of

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... storms.Using a dispersive long-wave model coupled with the significant wave model of the CoastalEngineering Research Center (CERC), the occurrence of potentially devastating storm surgeflooding around Manila Bay was numerically simulated. A unique characteristic of the new modelis the inclusion of the dispersive terms in the associated momentum balance equations. Deepwater gravity waves are always dispersive and inclusion of the dispersive terms is expected toprovide more accurate modelling results.The predictive capability of the model was verified using observations during the passage ofseveral storms including Typhoon Milenyo (2006) and Typhoon Pedring (2011). The occurrenceof the anomalously high storm surge of about 2.5 metres during the passage of Typhoon Pedringfar north of the area was correctly simulated. Numerical integration of the dispersive long-wavemodel with the addition of higher order terms in the momentum balance appears to give accuratepredictions of the coastal flooding due to storm surges and waves.The hydrodynamic set-down which occurs in many coastal areas during strong typhoons can besimulated well by the model. A new empirical model for the hydrodynamic force exerted by thecombined action of storm surges, waves, and extreme currents is also presented. Initial calculationsof hydrodydynamic forces generated by an actual typhoon crossing Manila Bay are discussed.