Tai O's typhoon dilemma

PUBLISHED : Sunday, 19 October, 2008, 12:00am
UPDATED : Sunday, 19 October, 2008, 12:00am

Janitor Lei Ah-yan knows all the ins and outs of Tai O village, he says, as he has lived there all his life, but at 71 he has never seen a typhoon like Hagupit, the fourth Hong Kong experienced over the summer, and its most destructive. 'Maybe my grandfather witnessed something like that, I don't know,' he said.

With the rare combination of a storm surge and high tide, Hagupit, a signal 8, wrought substantial damage on Tai O on September 22, and last week residents were still clearing water-damaged goods from their shops and houses.

Mr Lei has lived all his life in a stilt house and has a philosophical view of typhoons. 'It is God's will, there's not a lot you can do about it. If it comes, it comes. It's like the earthquake in Sichuan .'

But others have a different view. On Friday evening, legislator Leung Yiu-chung was to bring together government officials and villagers to discuss not only compensation for the villagers to help them recover from the storm, but their requests for a permanent storm shelter. More radically, they were to talk about whether the small town on the western tip of Lantau needs a high sea wall or floodgates or barriers along the lines of the River Thames estuary in London, or a rising levee system like that in New Orleans.

Perhaps the ultimate flood experts are the Dutch, having for centuries lived in a country that is below sea level. While for many decades the Netherlands relied on dykes, these days many of those have been supplemented with or replaced by storm-surge barriers.

According to a report in Science Daily, as the water rises, computers close the walls and fill the tanks along the barrier. This causes the walls to sink to the sea bottom, keeping most of the water from passing through.

In New York City, with its 8 million residents, engineers are also looking at providing protection, warning that with rising sea levels fromto global warming, the city could be at risk of catastrophic destruction and a huge casualty toll.

Tai O was lucky that there were no casualties despite the water rising to chest-high in certain areas. 'We're going to talk about how the flood affects the people, and we are trying to talk to government officials about flood barriers,' Mr Leung said ahead of the meeting.

'It requires some in-depth discussion,' said Mr Leung, who has represented New Territories West as a legislator for the Neighbourhood and Workers Service Centre since 1999. 'Tai O needs some form of floodgates. At this moment the government does not have a plan. It's not a question of money. It's only the beginning [of discussions]. It has a long way to go.'

German flood engineer Joerg Krywkow, who is based at the department of water engineering and management at the University of Twente in Enschede, the Netherlands, said what might be required in Tai O is a diversity of measures.

'A typhoon is a typhoon, and a village close to the coast needs protection. You can have a village with a dyke around it - it goes from one point and ends at another - but there is, of course, the possibility that you have a dyke and still get flooded, so you need an integrative approach.'

Mr Krywkow studies the risk-benefit approach, where the key issue is to protect people and assets, but also to assess several ways of carrying that out.

'There is the prevailing dogma in the Netherlands that to decrease the problem of being flooded you just increase the size of the dykes. But what we want to do is go beyond that by looking at land use - and keep less vulnerable sites such as fields and forests near the coast' so that they can be flooded with no danger to inhabited areas.

Tai O has mangrove swamps, which geologist Bernie Owen says could help slow down the wave action. When there is a direct hit from a powerful typhoon, waves throw up a lot of debris, including rocks, which can have a devastating effect.

'But the key thing about mangrove swamps is that there is no one living there. The problem is when people build on geologically hazardous areas.'

Professor Owen, of the geography department at Baptist University, says that flood barriers or a high sea wall would be an over-the-top reaction in Tai O.

'It would be devastating for the natural environment, as you would be changing the current flow. The cost of that, I would imagine, would be astronomical and it would not look good for tourism to have a high wall surrounding Tai O. Perhaps another solution would be to make the stilt houses a metre higher.'

Professor Owen said it was a matter of balancing risk and cost. 'How much money do you want to spend on an event that won't be that common? It depends whether it is once in 10 years or once in 100. It's still a lot cheaper to provide comprehensive compensation. What you have to assess are the recurrent risks.'

Those risks, says the Observatory, have not shown any signs of increasing, according to patterns over the past decade, but with rising sea levels caused by global warming, that could change.

Leung Wing-mo, a senior scientific officer at the Observatory, said: 'We have done some research that does not show increasing strains of strong typhoon. So far the past trend does not indicate this. But theoretically, with warmer sea temperatures and a warmer atmosphere, there is a basis to expect stronger typhoons in the future.'

With Hagupit, he said, there was a combination of natural events - including a significant storm surge - leading to wind speeds of 170km/h, coming from the west Pacific across the South China Sea in a west-northwest direction. Tai O's misfortune was the marriage of tide and storm surge, but the chances of that recurring were small.

For other areas of Hong Kong, said Professor Owen, it was a question of living away from a danger zone.

'For example, people who build houses on flood plains - they're called flood plains for a reason,' he said.

Tai O villagers also feel that they have been forgotten by the government.

Chan Sai-keung, 71, owner of a dry-fish shop, said the government had put forward an idea for a sea wall about 20 years ago 'but nothing came of it'. He said he would try to raise his shop floor using concrete.

According to resident David Liu Ping-ki, 60, it is a question of where to start.

'It would be such a huge project,' he said, sweeping his arm around the bay. 'It might be possible to build some kind of sea wall here, but what about on the other side of the village?

'As well as protecting the village, the residents need a proper shelter so they can go there in the event of a typhoon.'

Another resident, who asked not to be named, said Tai O was very vulnerable. 'It could disappear overnight in a big storm. There's no emergency relief plan in place, no plans on how to get fresh water, nothing.'

Shop owner Ho Chia-ching, who sells straw hats, estimates she lost about HK$20,000 in goods in the typhoon as the mud poured in. She pointed to a flight of steps next to her shop and said: 'It went up to the fourth step.'

Baker Alan Ngai Yiu-chung, whose shop was forced to close for a month, will open again for business this week.

'The sea water came in halfway up my industrial oven,' he said, pointing to his machinery. 'I was very afraid. In the near future another horrible storm may come. Building a sea wall would provide protection for the village.'

New Territories West legislator Tam Yiu-chung, chairman of the Democratic Alliance for the Betterment and Progress of Hong Kong, said: 'The government has said such an incident is very rare, only every 100 years or so, but we urge it to do more to prevent flooding.'

A spokesman from the Civil Engineering and Development Department said the Drainage Services Department, working with the Observatory, would develop a flood-warning system, but did not specify a timescale for this plan.

Unionist legislator Lee Cheuk-yan, who also represents New Territories West, said the priority was to ensure that the villagers received urgent relief. 'This time they have received compensation after means testing by the government [averaging] at HK$3,000. It's not enough,' Mr Lee said.

'The government should start a process of designing some protection for Tai O, not just a wall but in terms of design - something perhaps not so full of concrete and metal but something more pleasant that can blend in with the environment.

'I think this may cost money. But if this can prevent people and businesses from another flood, then economically it makes more sense.'