Fri, Nov 10, 2000 page12

• We must give rivers more space to breathe

  • By Chen Szu-hsien 陳賜賢
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  According to newspaper reports, two-thirds of all houses in Hsichih City (汐止市) are prone to flooding, while the remaining one-third, while safe from flooding, are not faring much better because they are located on mountain slopes. Residents of the flood-prone houses have to worry about rising flood water during typhoons, while those living in the mountain-slope houses lose sleep over the possibility of mudslides. On stormy nights, Hsichih certainly deserves the name "city of sadness." There is no guarantee of the people's right to be free from fear.

  The cause of past disasters has to be over-development, whose adverse effects are most evident during typhoons. To say that we will be able to avoid flooding after a clean-up of the Keelung River is complete is perhaps too optimistic. According to aerial photos from the former provincial government's department of agriculture and forestry, and in light of Hsichih's development over the past 10 years, mountain slopes make up more than two-thirds of the city, while the remaining one-third is a flood plain and is therefore not suitable for high-density development. There are also various restrictions on the development of mountain slopes. But over the past 10 years, Hsichih has been almost completely covered by tall buildings. The over-development is quite obvious.

  The NT$12 billion previously allocated for a clean-up of the Keelung River has now gone down the drain. But sometimes the handling of floods is not just a matter of money. Policies should have been given careful consideration. For example, detention basins (滯洪區) should not have been slated for urban development. The most obvious example has to be the new land generated by the straightening of the Keelung River. Land along the two bends of the river (大小灣段) is currently highly sought-after real estate, second only to the Hsinyi Project Area (信義計劃區).

  Downriver from Hsichih, the areas along the Keelung River are within the tidal reach, which means this section of the river is affected when the tide rises in the Tamshui River. It is therefore difficult to drain the water in that section. Under these circumstances, the river's flood detention capacity -- or the detention basin -- becomes very important because it can help delay the flood peak. Land reclaimed along the two bends of the Keelung River totals 277 hectares. At a depth of 1m, the area could have a flood detention capacity of 2.77 million m3,which might have spared the city from serious flooding.

  Previous surveys by the Taiwan Association of Hydraulic Engineers show that, during heavy flooding in Neihu's Tahu Shan-chuang Street (大湖山莊街), the water flow in the drainage system from the Tahu Park to the Keelung River is obstructed by the rising tide. The survey shows the impact on the drainage system along the river. Flooding in the Neihu area has its roots in the leveling and development of a river valley. Hsichih City is also in a similar situation.

  Future flood containment policy will still have to center around flood banks and pumping. Towering flood dams and a large number of pumping stations will not only prevent a dialogue between man and water, they will also become, in normal times, repositories of surplus waste water and garbage. Out of sight, out of mind, perhaps but Hsichih has lost an opportunity to become a world-class riverside city.

  If future construction on farmland is not regulated by overall land planning, the possibility of more flooding will continue. Respecting nature and designating more buffer zones and detention basins are the correct methods for sustainable land development.

  Chen Szu-hsien is chairman of the Taiwan Association of Hydraulic Engineers.

  Translated by Francis Huang
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