Learning from Cabalantian

Lahar, a Javanese word for mudflow, entered the vocabulary and consciousness of Filipinos only in 1991, soon after the eruption of Mount Pinatubo. Geologists appropriated the term and have been using it since the early 1900s to refer, not to mudflow, but, in the words of Dr. Kelvin Rodolfo, to “rapidly flowing mixtures of rock debris and water from a volcano.” We have long associated volcanic eruptions with boiling lava flows that glisten at night but pose no immediate threat. Pinatubo radically changed all that.

The other day, I heard local officials of Pampanga warn that some towns in the province might be facing a renewed threat from lahar because of the recent heavy rains. My impulse was to contact my good friend Dr. Raymundo Punongbayan to check if this apprehension had any basis. I was, of course, instantly jolted by the realization that he had been gone for quite some time now—this folksy man from Phivolcs who did more than anyone else to educate the Filipino public on the nature of earthquakes and eruptions and their consequences.

He and Kelvin Rodolfo, one of the very few scientists in the world who can claim an intimate knowledge of lahar, were regular guests on my television show, “Public Forum,” to bridge the gap between science and common sense. At no other time did government response and public awareness rely so much on the authoritative views of scientists like them. The question of what to do with Pinatubo dominated public discourse. The threat of new eruptions lingered for a couple of years after the first big explosion in June 1991. All kinds of ideas filled the air; one politician suggested, with all the earnestness he could command, dropping bombs into the crater of the awakened volcano.

When the threat of further eruptions died down, the debate shifted to what to do to protect low-lying communities from impending lahar. Many favored the construction of containment dikes. This was the most politically palatable, offering assurances that the scientists were, however, not prepared to guarantee. Others took the added precaution of building second floors to their homes, or raising them from the ground on sturdy stilts that made them look like bird houses.

The first waves of lahar, which came with the rainy season of 1991, were largely of the malabnaw (diluted) kind and not very different from the usual floodwaters that carry eroded soil. This bolstered the belief that lahar could be effectively arrested by the proposed dikes. The more the engineering solution was projected as the answer, the less urgent it became for residents to consider relocating to safer ground.

Scientists like Punongbayan and Rodolfo refused to be engulfed by the frantic call for action from the public and the political system. They approached Nature with awe and respect. It occurred to me then that they wanted the public to adopt the same respectful attitude in dealing with the natural forces unleashed by Pinatubo. This meant getting out of the path of these forces rather than foolishly hoping to contain or block them.

I e-mailed Kelvin the other day to ask whether he thinks the lahar threat in Pampanga persists to this day. From his office in the Department of Earth and Environmental Sciences in the University of Illinois at Chicago where he is professor emeritus, he replied: “A high-intensity rain of long duration can definitely cause a major lahar. We have to keep in mind that the Cabalantian disaster of 1995 was caused by remobilization of previous deposits that had buried Porac in previous years.” To this brief response, he attached a paper on Cabalantian that he had written but had not published. I was surprised to see that it is not the usual dry technical tract one expects from a natural scientist. This one is all about the people of Cabalantian in the aftermath of the tragedy.

The essay opens with a map showing Pinatubo, the Pasig-Potrero River and its secondary streams, the surrounding towns, and the tiny village of Cabalantian. “The most lethal disaster at Pinatubo volcano was not its 1991 eruption itself, Earth’s most powerful in almost a century. Pinatubo’s greatest calamity happened more than four years later. On Oct. 1, 1995, fierce typhoon rains whipped 50 million cubic meters of volcanic debris into monster lahars, thick slurries of sand and boulders that flowed rapidly down the Pasig-Potrero River. Cabalantian, a barangay or village in Pampanga province, 40 kilometers southeast of the volcano summit, had previously escaped the many lahars that had devastated so many other communities since the eruption. In a few hours the lahars buried it—erased it from the map.”

It took but six hours to bury 2,300 houses, 500 vehicles, and countless people. “Afterwards, the survivors would describe the flows as viscous, gray and brown, and smelling slightly sour, sulphuric. Surprisingly they were not at all hot, unlike the scalding flows experienced elsewhere. But the most impressive things about the flows were their depths, their speed—about 15 kilometers per hour—their power, destroying even hollow-block buildings, how they took along everything with them, floating even cars and big boulders.”

Based on actual interviews with survivors who had lost almost everything, Kelvin’s meditation concludes with the sad note that while the lahar could not have been stopped, the calamity itself could have been avoided. “May this story redeem some small value from the death and suffering in Cabalantian. Its dead and dispersed people will not have suffered entirely in vain, if others learn from the tragedy.”

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