Closer view , Dec. 1993, shows the effectiveness of the dike though still incomplete . These are natural occurrences which have serious impacts over large areas of the country, notwithstanding the devastating earthquakes and volcanic eruptions from time to time which cause enormous additional damage, especially the lahar or the mudflows caused by the debris of the Mt. Pinatubo Volcano. Each year about 20 typhoons occur in the Philippine Area of Responsibility of which an average of about 10 actually cross the country. The areas most affected by typhoon are marked in Map 1 below. The many typhoons and the irregular coastline make the Philippines extremely susceptible to storm surges.
High tides coinciding with storm amplify the surge.
The majority of victims of typhoons are by storm surges rather than by winds. Environmental degradation also increases the storm surge hazard. This includes destruction of mangroves, coral reefs and other forms of natural breakwater, siltation of river deltas, bays and gulfs, and shoreline reclamations. Areas most affected by storm surges are shown in Map 2. In July 1972, one of the worst floods occurred as a result of record rainfall for that month.