Mon, Jun 20, 2005 page8

• Disasters difficult to predict, but impact isn't

  • By Liu Chung-ming柳中明
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  Heavy rains, torrential rains and heavy torrential rains -- the rain keeps falling in southern and central Taiwan and the agricultural catastrophe grows as lowlying flooded areas expand. This situation is the curse of island nations.

  The majority of Taiwan's population is, however, concentrated in urban areas dominated by concrete buildings. Although pigs are drowned, ducks freeze to death, fish and shrimp are everywhere to be seen, fields are flooded, and houses in coastal villages collapse, few people are affected. Such is the character of climatic disasters in advanced nations: financial losses are high and human losses are low.

  This year, the peak of the rainy season has been extended, southwesterly winds continuously bring more rain. The rain-bringing mesoscale convective system is strong, and the torrential rains move slowly northwards along the Western side of the mountains. Steep mountain sides, economically valuable betel nut palm areas with loosely packed soil in southern Taiwan, rivers with much sand and stones but shallow river beds, renewed attempts at stopping seawater from flooding low-lying coastal areas, unsuccessful sewerage and water drainage canals and ditches lead to coastal areas being submerged -- this is Taiwan in times of climatic disaster.

  Taiwanese are quite used to this sight, but in their busy daily lives they forget the bitter lessons learned from past disasters. Among all the city dwellers who have left their homes in the countryside to seek a living in Taipei, there must be people from Sinyuan in Pingtung, Yanchao in Kaohsiung, Beimen in Tainan, Budai in Chiayi or Taisi in Yunlin.

  Seeing their kinsmen up to their waists or even necks in water, maybe they are happy to be in bustling Taipei, far away from tragic memories, wondering why rain-induced disaster always strikes their home. But more worrying is the thought that although Taipei was lucky not be hit now, who knows what will happen the next time.

  On the battlefield, it is not very likely that a bomb will fall twice on the same spot, and in Taiwan, we don't know where a July typhoon will bring disaster. When the rainy season is over, we have to wait for the next "bomb" to strike.

  Global temperatures have been rising for a long time, a phenomenon that is expected to accelerate over the next 100 years. High-temperature heat waves are more likely to occur and the number of dry and rainless days will increase. At the same time, vaporization will increase. This means that as the annual number of days with precipitation will tend to fall, the possibility of convective rainfall leading to copious rainfall in torrential rains will increase.

  That kind of precipitation, however, is not evenly distributed over the duration of a rainfall, but is sudden and unpredictable. As a result, single days with rainfall in excess of 200mm during the rainy season or typhoons are not uncommon. It is difficult to clearly predict where torrential rains will occur.

  Climatic and geographic factors are difficult to predict, and human improvements to the environment is what we must rely on.

  If regional water drainage projects had been completed, water would flow smoothly and quickly, making flooding less common. If mountain areas were full of deep-rooted Japanese cedar rather than betel nut palms, torrential rains would be less likely to cause mudslides and overflowing rivers.

  Now that the government is proposing a NT$80 billion water drainage improvement program, I can only say "better late than never," and "it's better do something than nothing."

  Liu Chung-ming is the director of the Global Change Research Center at National Taiwan University.

  Translated by Perry Svensson
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