4

Preeruption Awareness and Preparedness

HISTORICAL ERUPTIONS AND EXPERIENCE

Experience with disasters has long been recognized as an important factor that can influence what people—as individuals and in groups—perceive future risk to be, as well as what they do to mitigate and prepare for future events. Prior to the November 13, 1985 eruption of Nevado del Ruiz, however, recent history did not provide the people of Colombia with experiences to point out the dangers of the Ruiz volcano.

It has been estimated that some ten major eruptions of the Ruiz volcano have taken place during the past 10,000 years, occurring on an average interval of 160 to 400 years (Herd, 1986). The last major volcanic event at Ruiz was in 1595. In 1845, an earthquake, phreatic eruption (Herd, 1986), or avalanche (UNDRO, 1985) caused a giant mudflow that killed 1,000 people as it traveled 86 km down the Lagunillas River to the Magdalena River. This 1845 lahar traversed the current site of Armero (Acosta, 1850). Two significant earthquakes occurred in 1826 and 1827. Finally, in 1916, a more minor event resulted in ashfall in the city of Manizales in Caldas State. The volcano has remained virtually dormant since then.

The relatively minor eruptive events at Ruiz since 1595 and the lack of events of sufficient magnitude (from a social perspective) to illustrate lahar risk since 1845 did little to convince those at risk that volcanoes are a major and significant Colombian natural hazard.

This is illustrated by a 1985 Colombian Civil Defense publication, What to do in Case of Disaster. The booklet, which was prepared for public distribution, describes about a dozen hazards along with suggested protective public actions; volcanic hazard is not mentioned.

Pointing up this oversight is in no way an attempt to single out the



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 49
4 Preeruption Awareness and Preparedness HISTORICAL ERUPTIONS AND EXPERIENCE Experience with disasters has long been recognized as an important factor that can influence what people—as individuals and in groups—perceive future risk to be, as well as what they do to mitigate and prepare for future events. Prior to the November 13, 1985 eruption of Nevado del Ruiz, however, recent history did not provide the people of Colombia with experiences to point out the dangers of the Ruiz volcano. It has been estimated that some ten major eruptions of the Ruiz volcano have taken place during the past 10,000 years, occurring on an average interval of 160 to 400 years (Herd, 1986). The last major volcanic event at Ruiz was in 1595. In 1845, an earthquake, phreatic eruption (Herd, 1986), or avalanche (UNDRO, 1985) caused a giant mudflow that killed 1,000 people as it traveled 86 km down the Lagunillas River to the Magdalena River. This 1845 lahar traversed the current site of Armero (Acosta, 1850). Two significant earthquakes occurred in 1826 and 1827. Finally, in 1916, a more minor event resulted in ashfall in the city of Manizales in Caldas State. The volcano has remained virtually dormant since then. The relatively minor eruptive events at Ruiz since 1595 and the lack of events of sufficient magnitude (from a social perspective) to illustrate lahar risk since 1845 did little to convince those at risk that volcanoes are a major and significant Colombian natural hazard. This is illustrated by a 1985 Colombian Civil Defense publication, What to do in Case of Disaster. The booklet, which was prepared for public distribution, describes about a dozen hazards along with suggested protective public actions; volcanic hazard is not mentioned. Pointing up this oversight is in no way an attempt to single out the

OCR for page 49
people of Colombia for criticism. Few are able to recognize a hazard that, for all practical purposes, has not manifested itself for some 140 years. This lack of local experience with volcanic hazards, and, thus, the virtual absence of volcano risk perception among the Ruiz area residents, was likely a major obstacle faced by those scientists and officials who recognized the danger, engaged in preparedness for an emergency, and sought to ready the public to respond. INITIAL THREAT DETECTION The ability to predict the precise time and magnitude of a natural disaster depends on two factors: the current state of scientific knowledge about a particular disaster and local observations of precursor activities to the disaster. The earliest perception of threat associated with Ruiz was in December 1984. A landslide formed a dangerous natural dam. At about the same time, mountain climbers began to feel and report earthquakes and gas plumes. These activities persisted, and in February 1985 several geologists from INGEOMINAS (the National Institute of Geology and Mines) conducted a site visit. In March 1985, the Colombian Civil Defense (Defensa Civil de Colombia) and INGEOMINAS requested that the United Nations Disaster Relief Organization (UNDRO) send a scientist to study the volcano. John Tomblin of UNDRO inspected Ruiz in March 1985. Tomblin concluded that the observed earthquakes and gas plumes could be indicative of an eruption and he recommended that INGEOMINAS install seismographs to monitor the volcano. In addition, he suggested that a risk map be prepared to illustrate the potential hazard associated with an eruption of the volcano. Further, he recommended that the Defensa Civil de Colombia draft an emergency plan to facilitate public warnings and evacuation for high-risk areas. Thus, INGEOMINAS began a project to monitor and define the volcanic risk in the Ruiz vicinity. In May, UNDRO funded a reevaluation of Ruiz by Minard Hall of the Instituto Geofísico of the Escuela Politécnica Nacional of Ecuador. In May 1985, the U.S. Geological Survey initiated a cooperative effort with UNDRO to provide scientific equipment to monitor Ruiz. First steps began in July 1985 when four portable seismographs were installed on the mountain. At about the same time, the Ruiz Volcanic Risk Committee was formed. Its charge was to begin volcanic monitoring, local emergency planning, and public education about volcanic risk. In August, the installed seismographs recorded 5-20 earthquakes each day (Herd, 1986). INGEOMINAS pointed out that, on average, such earthquakes have, on a global basis, accompanied large volcanic eruptions about 25 percent of the time throughout recorded history. A minor eruption of steam, ash, and rock occurred on September 11, 1985; this event captured government attention although no one was injured. Surveillance of the volcano contin-

OCR for page 49
ued, and by October more seismographs and tiltmeters were installed on Ruiz. On November 12, 1985, the day prior to the major eruption of Ruiz, geologists who climbed to the summit to collect gas samples observed no clear signs of an imminent explosion. EFFORTS TO INCREASE AWARENESS A variety of efforts were undertaken to increase awareness of the risk presented by Nevado del Ruiz subsequent to the scientific discovery of an impending eruption and prior to the November 13, 1985 event. These efforts involved many Colombian and other organizations. Instituto Nacional de Investigaciones Geológico-Mineras (INGEOMINAS) In August 1985, INGEOMINAS published the first of a variety of reports designed to organize for or further the understanding of volcanic risk in response to the Ruiz threat. The first of these reports, Riesgos Sísmicos y Volcánicos Del Parque Natural De Los Nevados (Seismic and Volcanic Risks of Los Nevados Natural Park), was an effort to report on recommended research and monitoring on six Colombian volcanoes and the areas around them. The research agenda proposed recognized the volcanic risk in Colombia, particularly in volcanic regions where people lived close by. The report requested a budget to perform the recommended studies and recognized the inevitable involvement of international scientists in the study of Ruiz. The proposed project was designed to be undertaken in stages, and it recognized the need for additional funds and international assistance. It also pointed to the need to involve organizations at all levels of Colombian government—including local governments—to define risk and hazard. The preliminary request sought funding to prepare a volcanic risk map for Ruiz; it was recognized that such a map would be needed to help make good hazard preparedness decisions. A preliminary version of the risk map was completed on October 7, 1985, and it was accompanied by an explanatory report entitled Mapa Preliminar De Riesgos Volcánicos Potenciales Del Nevado Del Ruiz (Preliminary Map of Potential Volcanic Risks Associated with Nevado del Ruiz). An additional report accompanied the preparation of the risk map. This report, entitled Informe Preliminar De Las Actividades Desarrolladas Período Julio 20-Octubre 7 de 1985, explained that Ruiz was in a stage of activity but that it could not be precisely predicted when an eruption would occur. Continued volcanic activity was reported along with minor ashfall, de-icing of the mountain top, small mudflows, and increased volcanic crater size. The

OCR for page 49
report stated that there was a 100 percent chance of catastrophic lahars when Ruiz erupted. INGEOMINAS held a meeting in mid-October to introduce the October 7, 1985 risk map to other national agencies. The map was revised in November 1985 in a report issued on the 10th of that month, Mapa De Riesgos Volcánicos Potenciales Del Volcánicos Nevado Del Ruiz. This revised map and report were based on additional scientific data, but both maps foretold the total inundation of Armero in the event of an eruption. Finally, on November 10, 1985, INGEOMINAS issued a final preeruption report, Informe De Las Actividades Desarrolladas (Período Octubre 8-Noviembre 10, 1985) (see Figure 4.1 ) in which risk estimates were the most precise. Risk maps reached local communities and were posted in local civil defense offices. It was difficult for nongeologists (Congress and local officials) to accept the risk imposed by Nevado del Ruiz as revealed in the sequence of reports and maps issued by INGEOMINAS. For example, the Colombian Congress FIGURE 4.1 Risk map released on November 10, 1985, depicting risks associated with a future eruption of Nevado del Ruiz (original map in color).

OCR for page 49
criticized both INGEOMINAS and the Colombian Civil Defense for frightening people with their efforts to increase hazard awareness. Local civil defense and Red Cross personnel reported that city officials in Armero never did believe that their town was at risk; they also reported that the mayor of Armero still voiced his disbelief in the risk while talking on a phone at the very moment a lahar hit his building and took his life. Civil Defense The Colombian Civil Defense responded to the risk foretold by INGEOMINAS as early as April 1985. In the period between April and October 1985, Colombian Civil Defense spent some 5.3 million pesos on equipment to support emergency preparedness. These resources were expended on emergency communication equipment, uniforms and boots, ambulance tires, gas masks, emergency food and rations, and other items, including body bags. This effort to support preparedness and disaster response was spread throughout the entire area, in all the communities at risk. In September 1985, after hazard maps work was under way, the director of civil defense created a plan for emergency response to the risk and eruption of Nevado del Ruiz. The plan was based on an assessment of what still remained to be accomplished and was prepared in concert with the National Committee of Regional and Local Organizations, which was established to address the threat of an eruption of Ruiz. The plan consisted of planning elements and implementing procedures for the evacuation of risk areas. Additionally, in September 1985, the Colombian Civil Defense began flights over the mountain and river valleys near Ruiz to collect risk information. It was also in September that Civil Defense and INGEOMINAS met with Parliament to explain the risk of an impending eruption of Nevado del Ruiz and to discuss the resources needed for preparedness and mitigation, as well as the training needed to accomplish this work. October 1985 saw even more intense efforts on the part of Civil Defense to prepare for an eruption. Radio communications were augmented in quantity and quality with both fixed and mobile communication devices. This was done in the four states in which risk was present: Tolima (the state encompassing the city of Armero), Caldas, Risaralda, and Quindio. Representatives of these four states conferred with the Colombian Civil Defense at the national level to provide local input into the planning process and the preparedness plans themselves. Civil Defense volunteers from these same four states went to the towns and villages at risk to alert local officials to the danger and to disseminate information about what to do in the event of a disaster. Volunteers knew of the general risk of an eruption, but they lacked detailed information on the true dangers posed by lahars. This effort also included an attempt to build

OCR for page 49
up public confidence to “minimize the chance of public panic if and when a disaster occurred.” Civil Defense volunteers talked directly to local residents in areas at risk, including people in cities, towns, and smaller settlements, and also to squatters living along riverbanks. These conversations were an attempt to inform people about (a) what Civil Defense is, (b) the current general risk of an eruption of Ruiz, (c) preparedness for the disaster, and (d) initial aid after impact. The study team was unable to determine how many people were reached through such activities. The efforts of Civil Defense in October extended even further. A census of the population at risk was compiled along the Gualí, Recio, Lagunilla, Azufrado, and Chinchina rivers. This census was a detailed field count of permanent and transient inhabitants at risk. Civil Defense held conferences in the cities of Armero, Chinchina, and Honda to provide risk and preparedness information. Although the Colombian Congress had criticized both the Colombian Civil Defense and INGEOMINAS, claiming that their efforts to increase awareness might scare the public, the study team found no evidence of public fear resulting from the effort to inform those at risk. City and Regional Authorities The Tolima Regional Emergency Committee was comprised of representatives from a variety of organizations. These included the Governor’s Office, the Army’s Sixth Brigade, the Regional Health Services, Civil Defense, the Red Cross, INGEOMINAS, and others. The committee contacted officials in local towns and cities at risk to inform them of the need for emergency preparedness and to encourage the development of local evacuation plans. The risk, of course, varied from town to town, and the committee was able to initiate various kinds of preparedness activities in many locales. The regional committee met many times prior to the November 13 eruption, but its last two meetings were particularly noteworthy. On October 29, 1985, the Tolima Emergency Committee met at the office of the Red Cross. The information presented was elaborate. The risk map prepared by INGEOMINAS was presented and reviewed along with probability estimates for different events, including a worst case scenario. The monitoring activity associated with the volcano was outlined and discussed. Census data of the population at risk were presented. Emergency communications were reviewed by the Red Cross, as was the availability of some 3,000 Red Cross volunteer workers for disaster response. Additionally, the assistance reserves of some 150 countries was discussed as part of the disaster relief available. The meeting obviously made available a range of risk, preparedness, and disaster response information to some dozen at-risk communities.

OCR for page 49
On November 13, the day of the eruption, the Regional Emergency Committee held a regularly scheduled meeting beginning at 5:00 p.m. The president of the Red Cross reported before the meeting officially began that there had been ashfall in the northern part of Tolima. The committee asked a representative of the police to send word to central command to alert all police stations to prepare for mudflows and floods along the shores of the rivers. The Red Cross alerted its field staff by radio and advised that they closely monitor low-lying areas. The director of INGEOMINAS advised those at the meeting what to do about ashfall; this advice was also disseminated over radio to the Red Cross and the police. The meeting was then called to order. Three topics were discussed once the meeting was officially under way. First, the committee discussed with the police how best to communicate with outlying areas about the existing risk of ashfall and the potential risk of mud and flooding along riverbanks. Second, there was a detailed discussion of the agenda for a major committee meeting two days later on November 15, 1985. The agenda for this meeting was to be quite detailed and aimed at fine-tuning emergency response plans (for example, updating census data on river bank populations). Finally, the Red Cross reported that it had just received word by radio that the abnormal condition in northern Tolima had ended. Public Information In the weeks prior to the eruption, risk maps were distributed throughout the areas at risk in each city and town. Thousands of public information pamphlets were distributed (see Figure 4.2 ) and posted. For example, in September of 1985, public pamphlets were distributed in the State of Caldas that described mudflows and the magnitude of danger involved. In October, the Caldas emergency committee issued a new public brochure. It described the likely presence of environmental cues for the eruption (such as ashfall), as well as what people should do in response to the event. The public brochures for Tolima (the state containing Armero) discussed ashfall, volcanic gases, avalanches, inundation (especially along the larger rivers), explosions, and burning rock. The brochure also discussed what to do in an emergency: (a) in case of ashfall, remove the ash from your roof and cover your nose and mouth with a wet handkerchief; (b) in case of gases, use masks; (c) in case of avalanches or mudflows, evacuate zones near the shores of rivers and stay high in the hills. It was reported that, in response to public information, a few people simply moved away from the rivers in October 1985, especially after seeing unusually dirty water in the rivers.

OCR for page 49
FIGURE 4.2 A sample of the public information flyer distributed in the weeks prior to the eruption to thousands of Ruiz area residents at risk. The flyer describes recommended emergency measures in the event of a volcanic eruption.

OCR for page 49
CONCLUSIONS The efforts to share awareness of the magnitude of the risk imposed on Colombia by Nevado del Ruiz were extensive; hazard maps played a key role in the effort to educate local decision-makers. Risk was well recognized by INGEOMINAS, Civil Defense, the Red Cross, the Regional Emergency Committee, and others. This risk recognition was slower in coming for some groups than others. However, it was also reported to the study team that both the Colombian Congress and officials in Armero did not recognize the risk to be as great as did the other aforementioned groups. There was fear reported among members of Congress and on the part of local officials that citizens at risk would panic if they were told about the actual risk.