Not all natural catastrophes are the work of fate – some are man-made. However, the distinction is not always straightforward, particularly in the case of floods, landslides or wildfires.
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Natural catastrophes can cause immense economic and human losses. Floods, storms, earthquakes, droughts, forest fires and volcanic eruptions are among the most devastating types of natural catastrophe. But some disasters are man-made. These include explosions, major fires, aviation, shipping and railway accidents, and the release of toxic substances into the environment. However, the distinction between natural and man-made catastrophes is not always as clear cut as you might think. Some events are wrongly assumed to be natural catastrophes, as the following examples show.
Landslide at the Vajont Dam
On 9 October 1963 in the Italian Alps, 270 million cubic metres of rock and earth collapsed from the side of Monte Toc into the reservoir below, triggering a 150 metre tsunami which overtopped the dam. 25 million cubic metres of water rushed through the narrow canyon towards the village of Longarone at the bottom. This village and four others were almost completely destroyed and nearly 2,000 people were killed. The 262 m high concrete dam withstood the wave and still stands today virtually unscathed. Construction of the dam had been completed in 1960. During the filling process in 1962, the adjacent hillside began to move. Filling was immediately halted and the water level lowered. This seemed to work and the mountainside stopped moving. In April 1963, the filling of the basin was resumed – until the side of the mountain suddenly collapsed. Normally, a landslide into a lake and the resultant tsunami are entirely natural processes. However, the Vajont disaster was clearly a result of the filling of the basin destabilizing the mountainside. Without the dam, the mountain would not have started to slide and even if it had, there would have been no flood wave.
Dam breach in Tesero
Two mine-tailing basins were located near Tesero in the Trento region of Italy. The 34 m high dam of the upper basin collapsed on 19 July 1985. A torrent of debris and mud poured into the lower basin, causing its dam to fail as well. A 200,000 cubic metre mudflow rushed through the Stava valley at high speed, burying 268 people. Some databases list the event as a flood disaster. Yet the disaster was not due to extreme precipitation. The dam had been constructed to very low safety standards and was known to constitute a high risk. The collapse is believed to have been caused by a poorly installed drainage pipe.
Forest fires in Indonesia
In 2015, devastating forest fires raged across parts of Indonesia. Weather conditions there and in large parts of the world were heavily influenced by the climate phenomenon known as El Niño. Conditions were especially dry in the western Pacific region. In Indonesia, fires ravaged forests and bushland over tens of thousands of square kilometres. A dense mantle of haze covered large parts of Southeast Asia, in some cases for months on end. The consequences were dire: people had serious health problems, airports and schools had to be closed and public life suffered in general. Economic losses amounted to billions. Property losses alone are likely to exceed a billion US dollars. Yet it would be too simple to attribute this catastrophe exclusively to the El Niño phenomenon. The fires were started deliberately – to clear the forest. Due to the extremely dry conditions, however, the actual area burned was many times larger than originally intended. The catastrophe was therefore caused by a combination of man and nature.
Landslide in Shenzhen
On 20 December 2015, a massive landslide in southern China destroyed 14 factory buildings and more than a dozen office and residential buildings. Sludge and debris some six metres deep buried parts of the Hengtai industrial area on the edge of the Shenzhen Special Economic Zone. Around 70 people were killed. According to the authorities, an artificial dump of excavated soil and rubble had been brought down by heavy rains. The debris had evidently been piled up too high and too steeply and over the years had grown to a height of over 100 metres without the authorities taking any action. Even if heavy rains ultimately triggered the disaster, it was clearly a man-made incident.
Munich Re Experts
Head of Research, Hydrological Hazards in Geo Risks Research
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