LAHAR RISK MAPPING OF BANAHAW VOLCANO, SOUTHERN LUZON USING LAHARZ

Abstract

Banahaw Volcano is one of the 24 identified active volcanoes in the Philippines. With the growing population around its vicinity, it is important to produce hazard map and risk maps for Banahaw Volcano. Geographic Information System (GIS) tools could be utilized to determine the hazard areas in case of lahar flows. Risk assessment based on population of barangays can be determined using the Population Exposure Index (PEI), Population Risk Level (PRL) cohorts, and land area. Early versions of volcanic hazard maps were generated based on the information of type and extent of deposits, river channels and topography. This study explored the use of LaharZ as a tool in generating a hazard map for Banahaw Volcano which can be assessed for risks. Input parameters for the LaharZ include estimated volume, stream threshold, slope value, cone apex type and flow type. Risk assessment of the hazard map produced in LaharZ confirmed that a total of 18 municipalities and three cities, and 402 barangays for both Laguna and Quezon provinces could be affected by future syn--eruption type of lahar from Banahaw Volcano. Results also showed that the lahar flow paths could affect farther municipalities along the North--northwest, Northwest, Southwest and Southeast areas of Banahaw Volcano. A consideration for identification of possible evacuation sites and preparedness plans, and proper siting of critical facilities outside of the proximal hazard zone are highly recommended accompanied by conducting more comprehensive researches about Banahaw Volcano for additional resources that may have greater accuracy.