ISA HK/China --- HK Tree News (Typhoon Nesat passing through HK 台风 "纳沙" 给香港树木的影响)

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*** Our weekly Station Mail is for the information of Station Members only, but Station Mail has given up copyright & can be freely circulated. For administrative reasons, comments from outsiders are usually not entertained & may be circulated within our system locally & overseas. Please note Station Mail is sometimes given in Blog at http://isahkchina.blogspot.com/  in English, although images are usually not attached due to size. ***

Dear Station Members,

The typhoon "Nesat" took HK by surprise on Sep 29, 2011. It is rather unusual that HK would get a typhoon signal no. 8 in the end of September, way passed the Mid-Autumn Festival. For more information on the wind effects of the HK Typhoon warning system, please go to http://www.hko.gov.hk/informtc/tcService.htm  .

At typhoon signal no. 8, the wind speed is estimated to be around 63 - 117 kmh. If struck directly with this wind speed face-on, ISA research has shown that even healthy branches can break. However, since HK is a hilly country & trees are located in many different places, some may get the wind upfront, & others sheltered by the landscape. ISA research has shown that if the right tree is planted in the right place , & is given the proper maintenance (including Structural Pruning), this tree can resist wind better & is safer. For those species poorly selected with brittle wood, planted in a 1m x 1m tree pit surrounded by concrete, with a big crown without Structural Pruning; in typhoon, it is always Mother Nature makes the rules for them.

A newspaper report below has given a count of 400+ Tree Failures during the Typhoon Nesat.

Additional information on the same Tree Failures can be found at:

1. http://news.on.cc/cnt/news/20110929/bkn-20110929095517395-0929_00822_001.html

2. http://news.on.cc/cnt/news/20110930/bkn-20110930141933797-0930_00822_001.html

3. http://news.on.cc/cnt/news/20110929/bkn-20110929091955098-0929_00822_001.html

4. http://news.on.cc/cnt/news/20110929/bkn-20110929050234141-0929_00822_001.html  

5. http://news.on.cc/cnt/news/20110929/bkn-20110929035759102-0929_00822_001.html

6. http://news.on.cc/cnt/news/20110929/bkn-20110929034300326-0929_00822_001.html

7. http://news.on.cc/cnt/news/20110929/bkn-20110929033706145-0929_00822_001.html

8. http://news.on.cc/cnt/news/20110929/bkn-20110929003256058-0929_00822_001.html

As Nesat is the only typhoon reaching signal no. 8 in the year of 2011, & it is not considered to be a very strong typhoon, while there can be 400+ Tree Failures as a result of it, questions may be raised on how safe our urban trees really are, after rounds of Tree Risk Assessments (TRA) after 2008. Numerous "dangerous" trees have already been cut down, as a result of the recent TRA. Does it mean that we have to cut down even more trees to keep the Tree Failure incidents even lower? Or is there other consideration?

It is possible that the higher authorities may wish to review why so many Tree Failures could still happen, even though many TRAs are given. Would this be from looking at past design, tree selection, tree installation, regular inspection, etc.? Would Arborists be required to be involved from the design stage & sign off proposals to take up the liabilities, like in western countries?

The next stronger typhoon in 2012 may help to consolidate some of the above answers.

best regards,

Sammy Au
President (Station Manager) of ISA HK/China
Registered Consulting Arborist no. RCA#497 (http://isahkchina.blogspot.com/2010/12/isa-hkchina-first-rca-in-asia.html )
ISA Board Certified Master Arborist / Certified Tree Worker no. HK-0174BT (http://isahkchina.blogspot.com/2011/03/isa-hkchina-first-bcma-in-asia.html )
Independent Practicing Arborist no. IPA-010908 (http://isahkchina.blogspot.com/2010/04/isa-hkchina-hk-tree-news-14410-report.html )

"Providing treatment without in-depth diagnosis & research support is professional misconduct. "


"Casual tree assessor delivers wanton tree assessment. Mother Nature makes the rules."

会员们:

在2011年09月29日，一个毫无予见的台风 “纳沙” 突然吹袭香港。在香港来说，中秋节之后的九月底，台风的出现是相当不寻常的。有关香港台风系统，可参照以下网上连结: http://www.hko.gov.hk/informtc/tcService.htm  .

在8 号台风信号下，风速估计为每小时63 - 117公里。ISA的研究显示，如果直接面对如此高速的风吹，算是健康的枝干也有可能折断。香港的地形多山多变，树木生长在不同的地方，有树木身处当风位置，有些却被周围的环境所庇护。ISA的研究已经表明，在合适的地点种植适当的树种, 并给予适当的保养（包括结构性修剪），树木能更好的抵御强风和更安全。在台风吹袭下，种上木质脆的品种，种在只有一米平方的树洞，或容许树冠过大而不作修剪等等, 都是树木倒塌事故的原因。大自然始终会决定成败。

在以下的报导，台风纳沙曾做成超过400多起的树木倒塌事故; 其他的塌树事件可在以下的连结找到：

1. http://news.on.cc/cnt/news/20110929/bkn-20110929095517395-0929_00822_001.html  

2. http://news.on.cc/cnt/news/20110930/bkn-20110930141933797-0930_00822_001.html

3. http://news.on.cc/cnt/news/20110929/bkn-20110929091955098-0929_00822_001.html

4. http://news.on.cc/cnt/news/20110929/bkn-20110929050234141-0929_00822_001.html

5. http://news.on.cc/cnt/news/20110929/bkn-20110929035759102-0929_00822_001.html

6. http://news.on.cc/cnt/news/20110929/bkn-20110929034300326-0929_00822_001.html

7. http://news.on.cc/cnt/news/20110929/bkn-20110929033706145-0929_00822_001.html

8. http://news.on.cc/cnt/news/20110929/bkn-20110929003256058-0929_00822_001.html

“纳沙” 是2011年唯一达到八号信号的台风， 虽然它并未归类为强台风，但它却导致超过400多起树木倒塌事故。有人会问，经过多轮树木风险评估之后，无数的“构成危险”的树木已被移除，为何仍然有这么多的塌树事故发生? 这是否意味着我们必须移除更多树木，以减少树木倒塌事故?

有关当局可能须要检讨一下为何在进行多次树木风险评估后， 塌树仍然频繁？ 这会否和以往的园境设计、选种、树木种植或定期检查等有关呢？ 树艺师是否应该像西方国家一样，在树木的设计阶段就已经参与设计队伍，并在计划书上签署和负上一定责任呢?

在2012年，下一个较强的台风来临之后, 可能会带来一些答案。

此致

国际树木学会 中国地区分会 会长
欧永森
顾问树艺师号 RCA#497 (http://isahkchina.blogspot.com/2010/12/isa-hkchina-first-rca-in-asia.html )
资深树艺师 / 注册攀树师号 HK-0174BT (http://isahkchina.blogspot.com/2011/03/isa-hkchina-first-bcma-in-asia.html )
执业树艺师号 IPA-010908 (http://isahkchina.blogspot.com/2010/04/isa-hkchina-tree-news-14410-report.html )

“没有深入诊断及探究支持去作出治疗，是专业失误。”


“速成出来的树木评估员，只会作出胡乱的树木评估。大自然会决定成败。”


(以上由莊俊榮 注册树艺师 /市政树艺师号 HK-0009AM 翻绎。一切内容以英文版本为准。)


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