Wed, Jun 08, 2016 - Page 8 News List

Thorough policy on preventing floods vital

By Chang Yen-ming 張炎銘

The media have been full of images of the flooding at the Taiwan Taoyuan International Airport. It is embarrassing, to say the least, because it happened at the main gateway to Taiwan.

More than 10cm of rain fell in Taoyuan’s Pusin (埔心), Lujhu (蘆竹) and Guanyin (觀音) districts in just three hours. However, the water level in the Pusin River (埔心溪) only reached 0.91m and it did not overflow, which shows that the rainfall did not exceed drainage design standards.

Taoyuan International Airport Corp (TIAC) and the Taoyuan City Government are blaming each other. While the company’s response was not commendable, neither of them seem to understand the concept of comprehensive flood control.

Flood prevention requires an overall approach. Floodwater caused by torrential rain must be quickly directed toward the sea or stored some place, because flood protection concentrated on a single spot could easily cause damage in another area.

To protect cities, floodwater was sometimes allowed to accumulate in nearby fields, since a few days of flooded fields would not result in any major losses. However, this has since been replaced by detention ponds and the “sponge city” concept.

Flood prevention planning at the Pusin River must include airport drainage and there are culverts running to the airport, but it was still flooded although the river’s water level remained low.

Taoyuan should not think this is unrelated to the city, and the city government should look into why the drainage system did not have the intended effect.

In particular, when the Pusin River embankments were built, were the airport authorities informed that they should renew and improve the culverts to match the new embankment construction? If they were not, would the resulting situation with the strong Pusin River and the weaker culverts not indirectly be responsible for the flooding?

As for TIAC, if it thinks that simply having culverts in place means that the water would be drained away, it is wrong. If the culverts are placed too low, they will not be able to drain the water into the river when the river rises; one-way valves are needed, in combination with pump stations.

Furthermore, the company is building taxiways and a drainage system, which raises the question of whether the flooding was the result of blockages caused by construction materials and other garbage.

In 2000, Typhoon Xangsane resulted in several people drowning in a basement in Keelung; in 2001, Typhoon Nari wreaked havoc on the Taipei MRT system; and two years ago, Taichung residents drowned in an underpass.

When it comes to urban flood prevention, underpasses, subway systems and basements are all weak spots. During the torrential rain in Taoyuan, floodwater seeped into the basement causing a power outage at Terminal Two. If important electrical equipment is placed in the airport basement, surely that is an issue that could be easily solved by spending a little money to waterproof the electrical and machine rooms.

The underpass leading to the airport was closed due to flooding and travelers were forced to choose another way, leading to severe congestion. Have the airport authorities never considered that possibility during disaster response drills?

The Ministry of Transportation and Communications is planning to invite the Water Resources Agency and the Taoyuan City Government to a joint review of the culvert and drainage system, which is a move in the right direction.

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