Mt. Pinatubo, Post-eruption: Socio-economic and Cultural Gaps in Lahar Risk Management

Mount Pinatubo, a stratovolcano located at an intersection of three provinces: Pampanga, Zambales, and Tarlac in the Philippians erupted in 1991, five centuries after its previous explosion (Gaillard, 2008).  Pinatubo discharged  nearly 7 km³ of pyroclastic material on June 12th and 15th along with emitting 40km high ash plume (Gaillard, 2008). A day after its explosion, on June 13^th, Typhoon Yunya made its way over the primary waterways that flowed down from Pinatubo (Gaillard, 2008). As a complex event, the heavy rainfall from the typhoon mixed in with the ash deposits on the volcanic slopes, creating thick mudflows, known as lahars (Barclay, et al., 2008). Two million people were affected as a result of this post-eruption hazard, with more than 140,000 houses completely or partially destroyed, further impacting public infrastructures like schools, churches, and local farmland that was completely buried with mud deposits (Barclay, et al., 2008). The damage from the explosion coupled with the immediate lahars accounted to about one billion USD with a total damaged area of 700km² (Gaillard & Leone, 1999).

By early April of 1991, seismicity monitoring of Mt. Pinatubo along with the observance of frequent landslides had been underway by the Philippines Institute of Volcanology and Seismology (PHIVOLCS) as well as the United States Geological Survey (USGS) (Tayang & Punongbayan, 1994).  This forecasting enabled officials to declare a 10km radius danger zone around the volcano, followed by an evacuation declaration (Barclay, et al., 2008). In this initial evacuation, 20,000 indigenous Aeta were relocated from the mountain slopes, as well as the surrounding populations – primarily farmers who lived in the low-land areas (Seitz, 1998).

Mount Pinatubo’s explosion was an event that directs much positive recognition to the volcanologists and seismologists given that Pinatubo’s eruption was the second most powerful eruption in the 20^th century, with a value of 6 on the volcanic explosivity index scale (Gaillard & Leone, 1999). These officials were able to issue an evacuation in time, prior to the explosion, saving thousands of lives. However, this event also serves as an important learning point that reveals the socio-economic gaps in lahar risk management following the 1991 eruption (Gaillard & Leone, 1999). The number of fatalities from the initial eruption, as 957 individuals, is incomparable to the number of individuals who die yearly because of the returning lahars (Gaillard, 2008).  In 1995, Pasig-Potrero lahar flows killed 100 people in the municipality of Bacolor despite attempts at managing the lahars through an initial diking system (Gaillard & Leone, 1999). But, the Philippine government was still keen on their decision for the dike system and went ahead to start a 50-million USD dike plan known as Megadike (Gaillard, 2008).

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In addition to the lahar damage, several studies following 1991 were conducted to measure infrastructure and agricultural damage (Tayang & Punongbayan, 1994). Such surveys looked at roof damage, comparing roofs whose spans were over and under 5 meters as well as the wet and dry ash accumulation on these roofs that caused them to collapse (Tayang & Punongbayan, 1994). The U.S. Clark Air Base, 20km from the base of the volcano that was in charge of collecting these results, was able to very successfully conclude through density measurements that 400kg/m of ash was required for most of the roofs to collapse, and the actual results indicated deposits of 2,000kg/m and 1,6000kg/m of wet and dry ash respectively (Gaillard & Leone, 1999). What these findings failed to show was the socioeconomic status of the individuals whose homes were destroyed and had to be relocated (Seitz, 1998). There was little to no correlation made between the size of the roofs and the poverty-stricken families who lived under them (Gaillard & Leone, 1999). Although the combined damage from the ashfall and the lahar deposits considered the destruction to the rice crops, livestock, and fisheries in 1992, which contributed to 107 million USD, this was simply a recognition, not a practical means of providing families with economic stability through employment or adequate compensation for their losses (Gaillard & Leone, 1999).

The risk assessment and management of the lahars was primarily focused on the geophysical events, opposed to the socio-economic, or cultural and religious aspects that were interconnected with the lahar regions (Gaillard & Leone, 1999). Because of the annual monsoons that have amplified the post-eruption damage, locals have struggled to maintain their livelihood in the relocation centers and are distraught to consider such locations as permanent settlements for themselves (Gaillard & Leone, 1999). Of these locals, are the Aeta indigenous peoples who fear that the physical distance from the mountain is also distancing their cultural and religious closeness – they see the distance as a threat, not the lahars (Gaillard, 2008). So in order to maintain their social stability, the Aeta, along with other neighboring populations have attempted to reconstruct their homes from raw materials as their social stability is independent of the geophysical risk (Gaillard, 2008). The Philippine government was disconnected from this socio-cultural context and focused more on providing temporary solutions for these individuals (Gaillard, 2008).

This case study intends to examine how the Philippine government is educating the locals about the returning threats of the lahars, and whether they are able to dissolve the tensions between themselves and the locals of Bacolor and neighboring municipalities on socio-economic and cultural terms. Further analysis on whether alternative strategies to the diking system have been employed for lahar risk management will be considered.

Outline

Introduction:

• Description of the Event – date, location, affected areas and populations
• The intersection of the direct factors vs. indirect factors that contribute to the vulnerability of the locals
• Temporary actions the government took – resettlement centers and relocation

Risk Perception: Contributing Factors

• Differing views of the locals and the government – engineering practices and attempts at cultural understanding (Tayang & Punongbayan, 1994).

• Explain the underlying root causes of the socioeconomic divisions
• Communication Struggles and Language Barriers

Comparative Analysis:

• “Social volcanology” – How the government cooperated with the indigenous of  Mt.Merapi, Indonesia vs. the tensions at Mt. Pinatubo, Philippians (Donovan, Suryanto, & Utami, 2012).

Current state of the municipalities:

• Lahar risk management – government contributions and local efforts
• Economic stability of the relocated locals, cultural compensation, improved livelihood?

Final Thoughts:

• Learning points for future risk assessment for the Philippine government
• Rehabilitation deficiencies (Donovan, Suryanto, & Utami, 2012).

References

• Barclay, J., Haynes, K., Mitchell, T., Solana, C., Teeuw, R., Darnell, A., Crosweller, H.S., Cole, D., Pyle, D., Low.              C., Fearnley, C., & Kelman, I. (2008). Framing volcanic risk communication within disaster risk reduction: finding ways for the social and physical sciences to work together. Geological Society, 305, 163-177.
• Donovan, K., Suryanta, A., & Utami, P. (2008). Mapping Cultural Vulnerability in volcanic regions: The practical              application of social volcanology at Mt. Merapi, Indonesia. Environmental Hazards, 11 (4), 303-323.
• Gaillard, J.C. (2008). Alternative paradigms of volcanic risk perception: The case of Mt. Pinatubo in the PhillipinesJournal of Volcanology and Geothermal Research, 172, 315-328.
• Gaillard, J.C. & Leone, F. (1999). Analysis of the institutional and social responses to the eruption and the lahars of              Mount Pinatubo volcano from 1991 to 1998 (Central Luzon, Phillipines). GeoJournal, 49, 223-238.
• Seitz, S. (1998). Coping Strategies in an Ethnic Minority Group: The Aeta of Mount Pinatubo. Disasters, 22 (1), 76 90.
• Tayag, J.C. & Punongbayan, R.S. (1994). Volcanic Disaster Mitigation in the Phillipines: Experience from Mt.Pinatubo. Disasters, 18 (1), 2-15.