As Typhoon Fanapi swept across eastern and southern Taiwan on Sept. 19, it brought extremely heavy rainfall of 500mm to 800mm or more in six hours to Gangshan (岡山) and Ciaotou (橋頭) townships in Kaohsiung County and Nanzih (楠梓) and Zuoying (左營) districts in Kaohsiung City. That is well in excess of the 480mm deluge that can be expected to occur once every 200 years. In fact, we could expect this kind of volume to occur in these areas only once every 500 years. Such heavy rainfall is bound to cause flooding, whatever city it falls on.
Various media pundits and academics, however, have failed to judge this objectively. Instead, for their own political purposes, they have chosen to lash out at the Kaohsiung City Government. Such emotional criticism is hardly reasonable. It would have been better to have taken a more scientific approach.
When rain falls on a plain, it has to run through a drainage system, converging in streams and rivers before finally flowing into the sea. On this occasion, the flooded area included the aforementioned four townships and districts and spread over half of Kaohsiung City, about 210km2 in total. The drainage system for this lowland plain consists of just four rivers — the Agongdian (阿公店溪), Dianbao (典寶溪), Houjin (後勁溪) and Love (愛河) rivers. The discharge capacity of these four rivers, measured in cubic meters per second, is about 500 for the Love River, 600 for the Houjin River, 340 for the Agongdian River and 250 for the Dianbao River, adding up to 1,690m3 in all. If the average rainfall over six hours for the 210km2 that were flooded was 600mm, then the total amount of rain that fell on that area in that time must have been 126.3 million cubic meters.
Over the same period, all the drainage rivers in that area could only discharge 36.5 million cubic meters of floodwater — just 29 percent of the total — while the remaining 71 percent (89.8 million cubic meters) had nowhere to go. It could only sit there, flooding the area to an average depth of 43mm, or flow into low-lying areas where the flood would then be even deeper.
Another factor to be considered is that, as the center of Typhoon Fanapi moved out to sea near Tainan in the afternoon, powerful winds blowing in a counterclockwise direction drove a storm surge at least 1m high onto the coast of Kaohsiung. That, combined with the high tide that came in at dusk, blocked the floodwater from discharging into the sea.
With such a heavy rainfall and given the accompanying conditions, there was going to be a flood no matter who happened to govern Kaohsiung city and county at the time. The city and county governments must bear some responsibility for failing to dredge the drains beforehand and to provide plenty of sandbags to keep floodwater out of basements, as well as extractor pumps to pump out water when it got in. But other than that, it was a matter of waiting calmly in the emergency operations center, ready to handle any situation as it arose.
Indeed, at 6am on the day after the typhoon, the Kaohsiung City Environmental Protection Bureau’s garbage collection teams were fully mobilized to clear away fallen branches and shop signs. That task kept them working late into the night and they spent three days clearing trash until the job was done. They should be commended for their perseverance and efficiency.
In view of all this, consider the opinion of a professor who once served in a senior post at the forerunner of today’s Water Resources Agency. This professor claimed that seven flood detention ponds could have prevented the flood. It should be kept in mind that the most each detention pond could hold would be about 100,000 to 110,000 tonnes of floodwater. With tens of millions of tonnes of floodwater to deal with, that really would be like trying to put out a fire with a squirt gun.
Meanwhile, a candidate standing in the area that will become Greater Kaohsiung’s year-end election claimed that if she were elected, she could remove the threat of flooding in Kaohsiung in less than a year.
Such empty talk is mere electioneering and suggests that the candidate in -question really doesn’t have a clue.
Given that Kaohsiung’s urban drainage system can only handle the kind of rainfall that occurs every five to 10 years or so, and the rivers in the area can only discharge a downpour that happens once every 50 years, there was no way flooding could have been avoided under the conditions described above. What’s more, global warming may cause extra-heavy downpours to happen more and more often.
The only way to reduce the impact of heavy rainfalls is to designate wider reservations around streams and rivers, in which only low-intensity development should be allowed. When their drainage profile is widened, rivers can discharge floodwater more effectively.
Additionally, urban drains should be dredged before typhoons arrive. Sandbags should be stored or floodgates installed at the entrances to basements of large buildings so that residents can use them stop the basements from being flooded. Plenty of extractor pumps should also be available at all district offices so that they can be dispatched to pump water out of inundated basements.
Such measures could mitigate the damage caused by flooding and give less cause for know-it-all commentators to pontificate after the damage is done.
Shern Jian-chuan is a professor of marine environment engineering at National Kaohsiung Marine University.
TRANSLATED BY JULIAN CLEGG
Trying to force a partnership between Taiwan Semiconductor Manufacturing Co (TSMC) and Intel Corp would be a wildly complex ordeal. Already, the reported request from the Trump administration for TSMC to take a controlling stake in Intel’s US factories is facing valid questions about feasibility from all sides. Washington would likely not support a foreign company operating Intel’s domestic factories, Reuters reported — just look at how that is going over in the steel sector. Meanwhile, many in Taiwan are concerned about the company being forced to transfer its bleeding-edge tech capabilities and give up its strategic advantage. This is especially
US President Donald Trump’s second administration has gotten off to a fast start with a blizzard of initiatives focused on domestic commitments made during his campaign. His tariff-based approach to re-ordering global trade in a manner more favorable to the United States appears to be in its infancy, but the significant scale and scope are undeniable. That said, while China looms largest on the list of national security challenges, to date we have heard little from the administration, bar the 10 percent tariffs directed at China, on specific priorities vis-a-vis China. The Congressional hearings for President Trump’s cabinet have, so far,
US political scientist Francis Fukuyama, during an interview with the UK’s Times Radio, reacted to US President Donald Trump’s overturning of decades of US foreign policy by saying that “the chance for serious instability is very great.” That is something of an understatement. Fukuyama said that Trump’s apparent moves to expand US territory and that he “seems to be actively siding with” authoritarian states is concerning, not just for Europe, but also for Taiwan. He said that “if I were China I would see this as a golden opportunity” to annex Taiwan, and that every European country needs to think
For years, the use of insecure smart home appliances and other Internet-connected devices has resulted in personal data leaks. Many smart devices require users’ location, contact details or access to cameras and microphones to set up, which expose people’s personal information, but are unnecessary to use the product. As a result, data breaches and security incidents continue to emerge worldwide through smartphone apps, smart speakers, TVs, air fryers and robot vacuums. Last week, another major data breach was added to the list: Mars Hydro, a Chinese company that makes Internet of Things (IoT) devices such as LED grow lights and the
RSS