
The overflow of a barrier lake on the upper reaches of Matai’an Creek caused fatal flooding in Hualien’s Guangfu Township, drawing increased attention to other barrier lakes around Taiwan. Some of them have been reinforced and could be developed into travel destinations, like Shuiyang Forest in Alishan or Dream Lake in Yangmingshan. However, experts say that not all barrier lakes are the same. Only by proper monitoring and fortifying against potential disasters can we coexist with these so-called "mountain tsunamis."
Roiling floodwaters carrying sediment wipe away this bridge in an instant. This shocking scene was caused by the overflow of the Matai’an Creek barrier lake in Hualien’s Guangfu Township.
Chen Wen-shan
NTU geologist
Most barrier lakes naturally disappear by gradually losing water and breaking apart, making the dam walls slowly get lower before it naturally goes away. This is what usually happens, the best-case scenario. When this happens, it doesn’t hold much water.
Apart from allowing it to naturally disappear, barrier lakes can also be managed by compacting the surrounding soil and rocks, becoming a travel destination like Alishan’s Shuiyang Forest or Dream Lake in Yangmingshan. Heavy rains brought by typhoons wash large amounts of sediment that can fill the lakes. In 2002, a barrier lake formed by the Liwu River in Taroko Gorge. Since the edges were made of hard rock, officials used explosive to blast it away. Different conditions call for different approaches. But experts also warned that barrier lakes can be highly dangerous, like an alpine tsunami.
Lee Hong-yuan (Sept. 24)
Former minister of the interior
When it overflows depends entirely on the amount of rainfall. We can’t control the rain, so we can only study it and order an evacuation. Otherwise, the loss of life could be greater than anyone can imagine.
Although grand and beautiful, these barrier lakes conceal a hidden danger. They must be carefully monitored and prepared for to avoid calamity.
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#barrierlake #Mataian #Guangfu #flooding #mountaintsunami #naturaldisaster #publicsafety #geology #Hualien
花蓮光復鄉馬太鞍溪堰塞湖溢流,導致下游變成水鄉澤國,造成嚴重災情。災難過後,全台的堰塞湖,成了各界關注焦點。實際上,有的堰塞湖經過人工整治,有可能發展成生態旅遊景點,像是阿里山水漾森林、陽明山夢幻湖等。但水利專家也表示,每個堰塞湖的條件不同,唯有做好監控、提升防災韌性,才能跟這"山上的海嘯"好好共存。
滾滾洪水,夾雜大量砂石,整座橋瞬間被沖斷,怵目驚心。花蓮縣光復鄉馬太鞍溪堰塞湖溢流,造成嚴重災情。
[[台大地質系榮譽教授 陳文山]]
“一般堰塞湖的消失,自然消失來講,就是它慢慢溢流,慢慢去切割,讓你的這個壩體,慢慢降低,然後它自然而然,它就消失掉,這是一般來講,最好的狀況,這種情形來講,一般它的堰塞湖的量體是不大的”
解決堰塞湖最好的辦法,除了讓它自然消失,也能經由人工整治,夯實周遭土石,還可能像阿里山水漾森林、陽明山夢幻湖變成景點。颱風帶來豪雨,沖刷大量土石,也有望"填平"堰塞湖。2002年,花蓮太魯閣立霧溪旁的堰塞湖,因為壩體是堅硬的盤岩,當時採用放置炸藥爆破。條件不一樣,能採取的方案也不同。但專家形容,堰塞湖是一頭洪水猛獸,如同山上的海嘯。
[[前內政部長 李鴻源(9/24)]]
“什麼時候會溢流,就完全決定於你下多少的雨,那這個東西都不是我們能掌控的,所以我們也只能講,還好有做這樣的研究,有做這樣的疏散,不然人命傷亡,恐怕會比大家想像的還要大很多”
美麗又宏偉的堰塞湖,暗藏危機。人們也必須做好監測預警,提升防災韌性,才能與天災共存。
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