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Typhoon Mangkhut

Typhoon Mangkhut proves Hong Kong urban jungle is no place for trees

PUBLISHED : Monday, 24 September, 2018, 5:11pm
UPDATED : Monday, 24 September, 2018, 8:32pm

More than 1,500 trees fell when the extremely strong Typhoon Mangkhut hit Hong Kong on September 16 (“Balance needed on trees in green city”, September 21). These trees blocked many major roads throughout the city. Moreover, some fallen trees damaged some of the overhead cables of the MTR East Rail Line, thus causing significant disruption and delays to railway service in the New Territories and Kowloon. With roads and railways severely affected, traffic service in the city was seriously paralysed on the day following the typhoon.

As most of the road blockage was due to fallen trees, one line of argument could be: if these trees had not been there, most of our roads would not have been blocked.

Accordingly, something must be wrong with the policy of our Tree Management Office (“Experts question if 11 specimens on Hong Kong’s ‘Old and Valuable Trees’ list could have survived Typhoon Mangkhut with proper care”, September 22). In my opinion, it is because the work of this office is based on some major misconceptions.

Firstly, the conception that people and trees can live harmoniously together is just an ideal and can never work in populous areas like Hong Kong. This is because trees require large areas to stay healthy. Accordingly, we must make a choice between trees and people/facilities.

Watch: Historic trees felled by strongest typhoon since 1946

‘Worst post-typhoon tree situation’: long clean-up after Mangkhut

Secondly, it is assumed that, if a tree is healthy, it can remain in place without any stabilising measures. It is obvious that any office working under such a misconception will result in many trees in populous areas. However, these trees are likely to fail under a high wind load.

Consider replacing roadside trees with ‘concrete planters’ of small plants or shrubs

The obvious solution is to adopt an engineering approach of having a larger safety margin. Should this approach be adopted, many of the existing trees would be removed, unless protective measures are provided, and these might be expensive.

People might argue that we cannot resist the power of nature and that it is normal for strong storms to cause damage. But look at the lamp posts in Hong Kong – they could resist the high wind load because they have a strong foundation of concrete block embedded below ground.

Finally, the Tree Management Office should consider replacing roadside trees with “concrete planters” of small plants or shrubs. These will keep our environment green and, at the same time, are safer and cheaper to maintain. The MTR should also consider building strong fencing to protect overhead cables from falling trees or branches.

Dr Wong Hong-yau, Happy Valley