2016年6月20日 星期一

1906香港風暴15000人死1937死11000人

轉載自:http://www.weather.gov.hk/blog/b5/archives/00000074.htm

什麼是風暴潮?
當強颱風鮎魚(2010年最強風暴)上月接近香港時,有人擔憂它會否帶來風暴潮。

簡單來說,風暴潮是熱帶氣旋引致的海水上升。熱帶氣旋的風力(圖 1)是水位上升的主因,它的低氣壓(圖 2)是次因。



圖 1      風暴本身的風力引致的水位上升

                           


圖 2      風暴的低氣壓造成的水位上升


過去一百年左右,曾有兩次風暴潮造成嚴重傷亡,一次在 1906 年,另一次在 1937 年,分別造成 15,000 人和 11,000 人死亡

風暴潮的水位高度視乎水深和海岸線形狀而定。若風暴潮遇上天文大潮,後果會較為嚴重。

由於香港的地理位置,吹東風或南風時香港較易受風暴潮影響。這從我們知道熱帶氣旋的風總是向逆時針方向吹,便可以想像得到。

看看圖 3,這幅圖根據現存數據,顯示導致香港出現最高 20 次風暴潮的熱帶氣旋路徑。紀錄保持者是 1979 年的颱風荷貝,那次在新界東的大埔滘水位上升了 3.2 米。總的來說,圖中的熱帶氣旋路徑,要不是直接或幾乎襲港,便是在香港西方或南方掠過。




圖 3      導致維港出現最高 20 次風暴潮的熱帶氣旋路徑


比較上述路徑,可見鮎魚的路徑(圖 4)頗為不同。鮎魚一直與香港維持 400 公里的距離,期間港內水位僅上升了 0.7 米(圖 5),當中有 0.5 米是與東北季候風有關。換言之,鮎魚的風暴潮實際只有 0.2 米。




圖 4      強颱風鮎魚的路徑







圖 5      10 月 21 日(星期四)正午至 10 月 22 日(星期五)午夜鰂魚涌的水位


說起來,過去東北季候風亦曾造成輕微水浸。在冬天,強烈東北季候風加上天文大潮會將水位推高 (博主註:指東北強風會引起吐露港海水倒灌),曾令港島西區上環的低窪地區出現水浸。基礎建設改善後,這個問題基本消失。

由於風暴潮可以造成嚴重破壞,香港天文台於 70 年代曾進行計算和推演,以減輕風暴潮對新市鎮的威脅。為此,位於新界東的沙田等地區在填海時便額外填高了 3 米 。(博主註ㄧ:七十年代當時可能未有考慮海平面迅速上昇因素)。

在天氣預測中,每當有熱帶氣旋移近華南沿岸時,天文台會運行一個風暴潮模式,若發現有威脅的話,會預先提醒市民特別注意風暴潮的危險。


註ㄧ : Al Gore 戈爾 CCTV  Dialogue  8.7.2016 專題訪問中透露了本世紀海平面會上昇數公尺  https://www.youtube.com/watch?v=PYGhKq0Y3_A , 届時人口最為密集的沙田和大埔會不斷有嚴重的海水倒灌需要在吐露港入口處設閘 (彷似 Thames Barrier 1982).



李本瀅、胡宏俊


參考:

1. 黃梓輝、李健威,強烈季候風在香港引致的水位異常,第二十一屆粵港澳氣象科技研討會,中國,香港,2007 年 1 月 24-26 日
2. 黃永德、黃梓輝,香港的風暴潮預測,海洋災害預報技術研討會(中國北京) 2008 年 12 月 4-5 日

香港天文台 :風暴潮對沙田新市鎮的威脅

日本,荷蘭,泰晤士河,威尼斯,蘇州河口,上海沿海等多地已经陸完成防潮攔海大壩.歴史上吐露港曾發生多起嚴重海水倒灌,随着氣候變暖風暴潮增多(頻密至每數年一次),海平面上昇(100年内半公尺或更多),吐露港應預留適當地點以備他日籌建活動攔海大壩,若船灣淡水湖改作抽水蓄能用途(海水或淡水),建議泵房在壩内建設(向西近沙田方向),使抽水蓄能變成咸淡皆宜,毋需重建.

Source: Google map

------------------------------------------------------

参考文章:

1937年,一場風災使潮水由吐露港倒灌進沙田海,並使兩岸大片土地遭淹沒,造成嚴重傷亡。
1962年,颱風溫黛吹襲香港,沙田墟和沙田機場損毀嚴重(註—)。

http://bbs.tianya.cn/post-208-14649-37.shtml

註— 颱風溫黛吐露港的潮水上漲至海圖基準面以上5.2米,比正常高約3米;大埔滘的潮水更上漲至海圖基準面以上7.0米 Source: http://zh-hk.hongkong.wikia.com/wiki/颱風溫黛。


天文台前助理台長梁榮武提醒,本港今次是好彩,妮妲路徑稍偏移,足可掛10號波,威力勁如1962年的超強颱風「溫黛」。1962 年溫黛襲港期間,造成130人死亡,53人失蹤 2016年08月03日 http://paper.hket.com/article/1475587/妮妲威力遜 稍偏移足勁如「溫黛」?itc=10000

香港天文台:全球暖化影響吐露港風暴潮

星島日報 – 2013年6月29日
天文台台長岑智明表示,全球暖化令世界各地較易出現極端天氣,香港出現風暴潮等反常氣象的機會大大增加。

岑智明指出,全球暖化令許多冰川不斷溶化,估計至本個世紀末,全球的海平面可能會上升半米,令每數十年影響香港一次的風暴潮變為每數年一次,即熱帶氣旋在香港南部海面掠過,吸起並把海水推上陸地,令香港低窪地區出現水浸。


https://hk.news.yahoo.com/%E5%85%A8%E7%90%83%E6%9A%96%E5%8C%96%E6%88%96%E5%BD%B1%E9%9F%BF%E6%B8%AF%E9%A2%A8%E6%9A%B4%E6%BD%AE-024800331.html



香港天文台: 2009颱風黑格比在香港引起的風暴潮個案研究  黃永德 黃梓輝 


全球暖化令水位 上升(香港過去55 年水位上升約13 厘米),與黑格比相連的風暴潮湧至香港時剛巧遇上天文高潮,兩者的疊加作用下加劇了水位上升,使香港多處地方遭受海水淹浸。2008年9 月23 日晚間至9月24 日清晨,鰂魚涌錄得的最高水位達3.53 米,是自1962 年9 月颱風溫黛襲港以來的最高記錄。大埔滘錄得的最高水位為3.77 米,是自1979 年8月颱風荷貝襲港以來的最高記錄。利用SLOSH 模式進行模擬試驗,我們發現如果黑格比的移動路徑再靠近香港80 公里,大埔滘的最高潮位可高達5.7 米,鰂魚涌則4.5 米.

http://www.weather.gov.hk/publica/reprint/r813.pdf


香港天文台 :風暴潮對沙田新市鎮的威脅

過 去一百年左右,曾有兩次風暴潮造成嚴重傷亡,一次在 1906 年,另一次在 1937 年,分別造成 15,000 人和 11,000 人死亡。香港天文台於 70 年代曾進行計算和推演,以減輕風暴潮對新市鎮的威脅。為此,位於新界東的沙田等地區在填海時便額外填高了 3 米 博主註一:七十年代當時可能未有考慮海平面迅速上昇因素) 1979 年的颱風荷貝,那次在新界東的大埔滘水位上升了 3.2 米。

在天氣預測中,每當有熱帶氣旋移近華南沿岸時,天文台會運行一個風暴潮模式,若發現有威脅的話,會預先提醒市民特別注意風暴潮的危險。



註ㄧ : Al Gore 戈爾 CCTV Dialogue 8.7.2016 專題訪問中透露了本世紀海平面會上昇數公尺 https://www.youtube.com/watch?v=PYGhKq0Y3_A届時人口最為密集的沙田和大埔會不斷有嚴重的海水倒灌需要在吐露港入口處設閘 (彷似 Thames Barrier 1982).


http://www.weather.gov.hk/blog/b5/archives/00000074.htm



香港天文台: 2009年颱風黑格比在香港引起的風暴潮個案研究

香港天文台: 2009颱風黑格比在香港引起的風暴潮個案研究  黃永德 黃梓輝 

全球暖化令水位 上升(香港過去55 年水位上升約13 厘米),與黑格比相連的風暴潮湧至香港時剛巧遇上天文高潮,兩者的疊加作用下加劇了水位上升,使香港多處地方遭受海水淹浸。2008年9 月23 日晚間至9月24 日清晨,鰂魚涌錄得的最高水位達3.53 米,是自1962 年9 月颱風溫黛襲港以來的最高記錄。大埔滘錄得的最高水位為3.77 米,是自1979 年8月颱風荷貝襲港以來的最高記錄。利用SLOSH 模式進行模擬試驗,我們發現如果黑格比的移動路徑再靠近香港80 公里,大埔滘的最高潮位可高達5.7 米,鰂魚涌則4.5 米.


http://www.weather.gov.hk/publica/reprint/r813.pdf

英國基督教救助會研究:2060年大洪災 全球十億人受害

2060年大洪災 全球十億人受害

http://www.christianaid.org.uk/Images/act-now-pay-later-climate-report-may-2016.pdf  研究全文)


英國最新研究指出,在2060年以前,全球將有十億人深受洪災之苦,其中又以美國、印度和中國受害最深。(法新社)
2016-05-16  〔編譯陳正健/綜合報導〕英國基督教救助會(Christian Aid)最新研究指出,在2060年以前,全球將有十億人深受洪災之苦,其中又以美國、印度和中國受害最深,氣候變遷是導致世紀洪害的主要原因。
英國研究顯示,南亞將是洪災最為慘重的地區,印度城市孟買和加爾各答,孟加拉首都達卡(Dhaka)都將深受其害,估計至少有1100萬人將面臨洪災之害。
另外,亞洲城市像是上海、廣州、曼谷、仰光和胡志明市,可能也有數百萬人受到洪災的威脅,其中又以窮人受害最深。
在美國東南沿岸,邁阿密也將洪災不斷,預計財務損失高達3.5兆美元,紐約的財務損失也有2.1兆美元。
研究作者道伊格(Alison Doig)指出,南方的巨型城市(mega-city)例如加爾各答,當地居民最有可能因海平面上升以及雨量增加,受到生命的威脅。
最後研究呼籲,全球當務之急就是減低二氧化碳的排放,以抑止氣溫上升,只要各國通力合作,超級洪災是可以避免的。

http://news.ltn.com.tw/news/world/breakingnews/1698541 

The Japanese mayor who was laughed at for building a huge sea wall - until his village was left almost untouched by tsunami

Updated: 01:32 GMT, 14 May 2011
The huge sea wall and floodgates took 12 years to build and had been widely regarded as a £20million folly. But today one former Japanese mayor is being hailed as a saviour after the grandiose construction allowed his small town escaped the devastation wrought by the March 11 tsunami.
In the rubble of Japan's northeast coast, Fudai 岩手縣普代村 stands as tall as ever after. No homes were swept away. In fact, they barely got wet.The 3,000 residents owe their lives to the late Kotaku Wamura, who lived through an earlier tsunami and made it a priority of his four-decade tenure as mayor to defend his people from the next one.
The 51-foot-high gate, which was criticised as being a wasteful public works project in the 1970s, protected the town from the tsunami
The 51-foot-high gate, which was criticised as being a wasteful public works project in the 1970s, protected the town from the tsunami
The floodgate project was criticized as wasteful in the 1970s. But the gate and an equally high seawall behind the community's adjacent fishing port protected Fudai from the waves that obliterated so many other towns.                                          
                           


Since the tsunami, residents have been visiting his grave to pay respects.
'It cost a lot of money. But without it, Fudai would have disappeared,' said seaweed fisherman Satoshi Kaneko, 55, whose business has been ruined but who is happy to have his family and home intact.
Two months after the disaster, more than 25,000 are missing or dead.
'However you look at it, the effectiveness of the floodgate and seawall was truly impressive,' Fudai Mayor Hiroshi Fukawatari said.
Fudai Junior High School students clean their tennis court after the tsunami- but compared to other towns, they escaped relatively unscathed thanks to the sea wall pictured in the background
Fudai Junior High School students clean their tennis court after the tsunami- but compared to other towns, they escaped relatively unscathed thanks to the sea wall pictured in the background
Towns to the north and south also braced against tsunamis with concrete seawalls, breakwaters and other protective structures. But none were as tall as Fudai's.
The town of Taro believed it had the ultimate fort - a double-layered 33-foot-tall (10-meter-tall) seawall spanning 1.6 miles (2.5 kilometers) across a bay. It proved no match for the tsunami two months ago.
In Fudai, the waves rose as high as 66 feet (20 meters), as water marks show on the floodgate's towers. So some ocean water did flow over but it caused minimal damage. The gate broke the tsunami's main thrust. And the community is lucky to have two mountainsides flanking the gate, offering a natural barrier.
Fudai, about 320 miles (510 kilometers) north of Tokyo, depends on the sea. Fishermen boast of the seaweed they harvest. A pretty, white-sand beach lures tourists every summer.
But 10-term mayor Wamura never forgot how quickly the sea could turn. Massive earthquake-triggered tsunamis flattened Japan's northeast coast in 1933 and 1896. In Fudai, the two disasters destroyed hundreds of homes and killed 439 people.
'When I saw bodies being dug up from the piles of earth, I did not know what to say. I had no words,' Wamura wrote of the 1933 tsunami in his book about Fudai, 'A 40-Year Fight Against Poverty.'
Even current Mayor Fukawatari, who helped oversee construction, had his doubts
Even current Mayor Fukawatari, who helped oversee construction, had his doubts
He vowed it would never happen again.
In 1967, the town erected a 51-foot (15.5-meter) seawall to shield homes behind the fishing port. But Wamura wasn't finished. He had a bigger project in mind for the cove up the road, where most of the community was located.
That area needed a floodgate with panels that could be lifted to allow the Fudai River to empty into the cove and lowered to block tsunamis.
He insisted the structure be as tall as the seawall.
The village council initially balked.
'They weren't necessarily against the idea of floodgates, just the size,' said Yuzo Mifune, head of Fudai's resident services and an unofficial floodgate historian. 'But Wamura somehow persuaded them that this was the only way to protect lives.'
Construction began in 1972 despite lingering concerns about its size as well as bitterness among landowners forced to sell land to the government.
Even current Mayor Fukawatari, who helped oversee construction, had his doubts.
'I did wonder whether we needed something this big,' he said in an interview at his office.
Japanese soldiers pray for tsunami victims. Two months after the disaster, more than 25,000 are missing or dead.
Japanese soldiers pray for victims. Two months after the disaster, more than 25,000 are missing or dead
The concrete structure spanning 673 feet (205 meters) was completed in 1984. The total bill of 3.56 billion yen was split between the prefecture and central government, which financed public works as part of its postwar economic strategy.
On March 11, after the 9.0 earthquake hit, workers remotely closed the floodgate's four main panels. Smaller panels on the sides jammed, and a firefighter had to rush down to shut them by hand.
The tsunami battered the white beach in the cove, leaving debris and fallen trees. But behind the floodgate, the village is virtually untouched.
Fudai Elementary School sits no more than a few minutes walk inland. It looks the same as it did on March 10. A group of boys recently ran laps around a baseball field that was clear of the junk piled up in other coastal neighborhoods.
Their coach, Sachio Kamimukai, was born and raised in Fudai. He said he never thought much about the floodgate until the tsunami.
'It was just always something that was there,' said Kamimukai, 36. 'But I'm very thankful now.'
The floodgate works for Fudai's layout, in a narrow valley, but it wouldn't necessarily be the solution for other places, Fukawatari said.
Fudai's biggest casualty was its port, where the tsunami destroyed boats, equipment and warehouses. The village estimates losses of 3.8 billion yen ($47 million) to its fisheries industry. One resident remains missing. He made the unlucky decision to check on his boat after the earthquake.
Wamura, who died in 1997 at age 88, left office three years after the floodgate was completed.
At his retirement, Wamura stood before village employees to bid farewell: 'Even if you encounter opposition, have conviction and finish what you start. In the end, people will understand.'



"Even if you encounter opposition, have conviction and finish what you start. In the end, people will understand."
-Kotaku Wamura   

http://www.oistbpl.com/Event_Detail.aspx?nid=226&type=r 

 村民们在海啸后纷纷到提议修建它的Kotaku墓前表达谢意与敬意。Kotaku早年经历过大海啸,死里逃生当选村长后,他认为自己有责任修建一座海堤,使后来的村民免受海啸威胁。
  工程始建于1972年,花费35亿多日元在1984年最终完工。海堤宽205米,高15.5米,并装有一个水闸以引普代河河水进入村庄,同时防御海啸。
  Kotaku在海堤修好后第三年退休。1997年,88岁的他去世。  http://news.sohu.com/20110516/n307596283.shtml