台湾“莫拉克”台风诱发山地灾害成因与启示

Formation and Mitigation Countermeasure of Geo-hazards Caused by Moarc Typhoon in Taiwan

2009-07"莫拉克"台风在台湾岛内滞留大于40h,受中央山脉地形以及西南季风的影响,形成"北部风强,南部雨大"的局面。本次降雨为台湾历年之冠,24h降雨量1825mm,48h雨量2467mm,逼近世界降雨极值。全台湾计有31个雨量站过程降雨量超过1000mm,23个雨量站超过1500mm,15个雨量站超过2000mm,南部部分区域甚至出现6～10日累积降雨量超过其年降雨量情形。最大总雨量位于阿里山,2009-08-06～10累计雨量达2884mm。长时间持续强降雨,造成了大量的泥石流、堰塞湖、崩塌、滑坡、山洪等山地灾害。大量的崩塌、滑坡阻塞河道,形成了16处堰塞湖。这些灾害淤埋村镇,毁坏道路、桥梁、堤防、建筑、输电和通讯设施。由于道路交通受损,电力、通讯信号中断,使得许多村庄与外部隔绝,成为孤岛,救援设施与救援物资无法到达灾区,延缓救援进度。受灾较重的乡镇有高雄县甲仙乡、桃源乡、六龟乡、那玛夏乡、杉林乡,南投县鹿谷乡、信义乡、国姓乡,嘉义县阿里山乡、梅山乡、中埔乡,屏东县高树乡、三地门乡、春日乡,台南县南化乡,台东县金峰乡等。截至2009-08,造成全台共619人死亡、肢体74件、76人失踪,其中小林村和新开部落被完全毁灭。台风暴雨、陡峻地形和丰富的松散固体物质等自然因素决定了山地灾害形成的基本因素,高强度长历时的暴雨是直接激发因素,坡地过度开发、道路建设、河道不合理利用等人为因素则加剧了灾情。莫拉克台风暴雨灾害对人们的启示是合理确定开发度,科学利用土地资源;确保山区溪流行洪空间,把防洪需求作为河谷地开发的限制条件;注意环境保育,尽量减少工程建设对斜坡的扰动;提高山地灾害预警标准,建立巨灾监测预警机制;进行灾害风险分析与管理,开展有机结合资源利用与减灾防灾的流域理性开发。

Moarc Typhoon standed over 40 hours in Taiwan island and gave rise to intensive rainfall and many geo-hazards,which resulted in a lot of lives casualty and properties loss.Due to the combination of central mountains in Taiwan Island and southwest monsoon,the weather had the features with intensive wind in the north and extreme rainfall when Moarc Typhoon control Taiwan Island.The rainfall intensity,with the 1 825 mm of 24 hours rainfall and the 2 467 mm of 48 hours rainfall,was the highest of Taiwan rainfall records and approached the terminal of the world rainfall.The data from rainfall observation stations of Taiwan show the rainfall exceeded 1 000 mm in 31 stations,1 500 mm in 23 stattions and 2 000 mm 15 stations.Furthermore,the accumulation rainfall from August 6th to August 10th was more than the annual rainfall in some areas of the south,and the maximal rainfall occurred at Ali mountain areas and reached 2,884 mm.The durative intensive rainfall trigged large numbers of geo-hazards including flashfloods,debris flows,collapses and landslides,which blocked rive channels and created 16 dammed lakes.These geo-hazards buried towns and villages and damaged quantity of highways,bridges,dikes,constructions,power and telecommunication facilities.Due to transportation block and power and telecommunication halted,many villages became isolated island so that the rescue facilities and materials could not be delivered and served in time,which postponed the rescue.When the Typhoon hit,16 townships were heavily damaged,including Jiaxian,Taoyuan,Liugui,Namaxia and Shanmu of Gaoxiong County,Lugu,Xinyi and Guoxin of Nantou County,Alishan,Meishan and Zhongpu of Jiayi County,Gaoshu,Shandimen and Chunri of Pingdong County,Nanhua of Tainan County and Jinfeng of Taidong County.By September 8th,Moarc Typhoon and the geo-hazards had caused 619 persons dead,76 persons missing and 74 persons injured,and Xiaolin valliage and Xinkai tribe had been destroyed completely.Through analyzing the formation causes of mountain hazards induced by Moarc Typhoon,it was found that Typhoon rainstorm,steep landform and abundant loose solid martial provided favorable natural conditions for mountain hazards forming,durative high-intensity rainstorm directly triggered mountain hazards and irrational human activities,including slope land overly development,highway construction and river channel unreasonable exploitation,aggravated the hazards loss.Then,based on the lessons of Moarc Typhoon and the induced geo-hazards,the mitigation measures were put forward The mitigation lessons and measures were put forward as follows：（1）scientifically utilizing and developing land resources on the basis of rational exploitation degree,（2）Ensuring adequate flashflood drainage channel in mountain stream and keeping the flood-prevention requirement as the precondition of valleys development,（3）strengthening environment protection and decreasing in utmost the disturbance and breakage of slopes induced by engineering construction,（4）improving early-warning standards of mountain hazards and building monitoring and warning systems of catastrophes,and（5）carrying out risk analysis and management of disasters and making rational watershed development integrating natural resources utilization and disaster prevention and mitigation.