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14 Mount St. Helens and Nevado del Ruiz: Warnings Heeded and Ignored A large loss of life was averted on May 18, 1980, when Mount St. Helens volcano in Washington state erupted. The eruption devastated an area as far as 29 kilometers from the volcano - causing landslides, debris flows, and floods. Total eco- nomic losses are estimared at $860 million. Two years before the blast, scientists had identified the volcano's potential hazards. When it began to show signs of renewed activity beginning in late March 1980, apparently building toward a major eruption, the hazard zone was evacuated. Land use of the area had been so restricted that when the volcano finally erupted eight weeks later, only 57 lives were lost due to the blast and associated landslide and fire. More than 22,000 Colombians were killed as a result of a relatively small volcanic eruption on November 13, 1985, when Nevado del Ruiz, the northernmost active volcano in the Andes, erupted. Hot volcanic ash scoured and melted part of the ice cap on the volcano's summit, triggering debris flows that swept down river valleys and overran villages in their path. The catastrophic loss of life, caused by a failure in emergency response, could have been averted. Colombian and international scientists, alerted by nearly a year of precursory activity, had warned that Ruiz might erupt and had prepared a hazard zoning map that accurately predicted the tragic effects of the eruption weeks earlier. Japan and Los Angeles: Landslide Prevention Probably the world's most comprehensive pro- gram of reducing landslide losses is in japan. Its strong national program of landslide control has sharply reduced the risk of death or property loss from the high levels of 30 years ago. Beginning in 1958, the Japanese government enacted strong legislation to prevent landslides. It provided for land use planning and construction of check dams, drainage systems, and other physical con- trols to prevent slope failures. These measures have met with great success. In 1938, nearly 130,000 homes were destroyed and more than 500 lives lost in landslides. Yet in 1976- the worst year for landslides injapan in the last two decades - only 2,000 homes were destroyed and fewer than 125 lives lost. Since then, the numbers have improved still further. The city of Los Angeles also has an impressive program to reduce landslide damage. Until 1952, controls on hillside grading and development in Los Angeles were limited. Then, after severely damaging winter storms, the city adopted a grading code that instituted procedures for safe development of hillsides. The grading regulations were significantly improved in 1963, The benefits of these regulations are a clear drop in the risk of landslide damage on sites developed after 1963. For example, during the severe storms of 1978, for a comparable number of sites, the damages to sites developed before 1963 were more than 10 times greater than to those sites developed after 1963. Sanriku, japan: Success Against Tsunamis In 1896, a tsunami generated by a nearby earth- quake struck the Sanriku district of japan, several hundred kilometers north of Tokyo. The max- imum run-up (heighr of the wave) recorded in this region was approximately 30 meters, and thou- sands lost their lives. Nearly 40 years later, in 1933, another major tsunami from a local earth- quake struck the region, killing about 3,000 and causing significant property damage. Again in 1960, the Sanriku district suffered a serious tsunami generated in Chile; about 200 people died and property valued at $50 million was lost, These events led to construction of major protective structures, land use management, and a district warning system to protect coastal commu- nities from serious inundation. One example is the seawall built by the town of Taro. About 8 meters high, it is shoreward of the fishing harbor, which itself is protected from storm waves by a breakwater. With an adequate warning system, the area can now be evacuated to the town in case of an approaching tsunami. In 1960, the Chilean tsunami flooded the center of the city of Of una to, also located in the Sanriku district, to a depth of several meters. Since then, a massive tsunami breakwater was built across the entrance to Of una to Bay. It protected the city from at least one local tsunami in 1968. Several kilo- meters north of Of una to, a similar structure was built at Kamaishi to protect the local steel indus- try and fishing fleet. Thus, japan has effectively protected itself in selected regions from serious damage by combining large protective structures with effective land use management. }