Severe Typhoon Mangkhut highlights perils of massive reclamation by Lantau

Typhoon Mangkhut helped show “storm surge” is a threat to modern cities, not just something for the history books.

On 7 September, the Post published an opinion piece by me (“What Kansai airport flooding can teach Hong Kong about the perils of reclamation amid climate change”), saying the disaster wrought by Typhoon Jebi in Japan should sound a warning to those planning reclamation in East Lantau, who do not account for the rise in sea levels or the increased intensity of typhoons that climate change could bring.

Perhaps this seemed a far-fetched notion given the rarity of typhoons with storm surges here in recent decades, yet nine days later Typhoon Mangkhut struck Hong Kong, bringing record-breaking storm surge along with waves whipped by ferocious winds. The astonishing videos of waves pounding into places including Shek O, Sai Kung, Tseung Kwan O and Heng Fa Chuen helped show what “storm surge” really means and – like Typhoon Jebi – showed it is a threat to modern cities, not just something for the history books.

The surge of 2.35 metres at Quarry Bay was higher than the 2 metres planned for in Our Hong Kong Foundation’s proposal for an Enhanced East Lantau Metropolis [later part of HK Govervnment’s “Lantau Tomorrow Vision”], and made higher still by the mighty waves. Hence, this clearly demonstrated storm surge can pose a threat to a metropolis built on an artificial island in the Western Harbour.

It is surely tempting to respond that surges are rare, or that engineering solutions like a higher island platform can safeguard the island.

Yet a Hong Kong Observatory account of Typhoon Wanda, which caused a major storm surge in 1962, notes that “Destructive tidal surges were reported in Tolo Harbour in 1874, 1906, 1923 and 1937” – and this, along with other historical records – suggests that storm surges are not really uncommon here, but have been unusually scarce recently.

Further, in some ways Hong Kong was lucky with Typhoon Mangkhut, which lost some strength as it crossed Luzon, and passed 100km to the south during daytime, when the forecast tide was a metre lower than at night. This means even more intense storms are possible; and as sea levels rise, storm surges will become even more of a threat.

Planners fixated on the East Lantau Metropolis ideas may call for engineering solutions like building the island platform even higher – rather as Kansai Airport’s defensive wall was raised, ineffectually as it turned out. But surely the best option is to build elsewhere, such as on brownfield sites, even though there are some challenges to tackle.

A letter to the South China Morning Post.

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One comment

Martin Williams

25 October 2018 / 8:57 am Reply
HK govt looking at countering storm surges

Better late than never, I suppose; should have been done earlier based on history and science, not simply reactive like this:

Holding back the tide: Hong Kong government commissions study to find ways of stopping sea from flooding communities during superstorms and typhoons
Development secretary Michael Wong says study is expected to take between 18 months and two years

Move has been prompted by Typhoon Mangkhut, which caused devastation in low-lying areas

https://www.scmp.com/news/hong-kong/politics/article/2170047/holding-back-tide-hong-kong-government-commissions-study

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Holding back the tide: Hong Kong government commissions study to find ways of stopping sea from flooding communities during superstorms and typhoons

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