Debris flow disaster at Larcha, upper Bhotekoshi Valley, central Nepal
Debris flow disaster at Larcha, upper Bhotekoshi Valley, central Nepal
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DOI：
10.1111/j.1440-1738.2005.00495.x
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发表时间：
2005-12
期刊：
影响因子：
1.5
通讯作者：
D. P. Adhikari;S. Koshimizu
中科院分区：
文献类型：
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作者：
D. P. Adhikari;S. Koshimizu
摘要滑坡和泥石流是喜马拉雅地区常见的灾害，特别是在夏季风期间。1996年7月22日，尼泊尔中部巴特科希河谷上游阿尔尼科公路109公里处的拉查发生了一场由拜拉布昆达河驱动的灾难性泥石流，悲剧性地说明了这一事实。在拉查的22座房屋中，有16座被冲走，两座部分受损，54人在几分钟内死亡。这一事件引起了人们的关注，因为媒体将其与冰川湖溃决洪水联系起来，因为河流的源头是冰川湖。为了了解该盆地的成因、形成机制和沉积过程，从地质、地貌和工程地质角度对盆地进行了研究，并对降水的作用进行了评价。降雨、悬崖面径流和河流底切的组合引发了公路上游500 m处倾斜和反倾斜斜坡上基岩和崩积层的破坏。滑坡碎屑堵塞了最终被破坏的通道，并沉积了约104 000 m3的粗碎屑，主要由小喜马拉雅起源的变质沉积物组成，并淹没了Larcha村。对碎片存款的碎屑大小、成分、结构和尺寸进行了研究。在泥石流源区，缺乏分选和存在大量的淤泥和粘土有助于泥石流的发生。丰富的小喜马拉雅变质沉积物碎屑加上没有碎片痕迹上游的滑坡现场排除了冰湖溃决洪水的可能性。这场灾难是降水、溪流侵蚀和突然决堤引发的山体滑坡造成的。
Abstract Damage, destruction and casualties related to landslide and debris flow are common phenomena in the Himalaya, especially during the summer monsoon. This fact was tragically illustrated on 22 July 1996, when Larcha, situated at the 109‐km mark of the Arniko Highway, upper Bhotekoshi Valley, central Nepal, experienced a catastrophic debris flow powered by the Bhairab Kunda Stream. Of the 22 houses in Larcha, 16 were swept away, two were partially damaged and 54 people were killed in a matter of a few minutes. The event attracted attention when media linked it to a glacial lake outburst flood as a result of the fact that the source of the stream is a glacial lake. To understand the cause, initiation mechanism and deposition process, the basin area was studied from geological, geomorphologic and engineering geological points of view and the role of precipitation was evaluated. A combination of rainfall, runoff from cliff faces and stream undercutting triggered failure of the bedrock and colluvium, both on the dip and counter‐dip slopes, 500 m upstream from the highway. The landslide debris dammed the channel, which was eventually breached, and deposited approximately 104 000 m3 of coarse debris, dominated by the metasediments of the Lesser Himalayan origin, and overwhelmed the village of Larcha. The debris deposit was studied for clast size, composition, texture and dimensions. Lack of sorting and the presence of abundant silt and clay in the source area helped in the initiation of debris flow. The abundance of the Lesser Himalayan metasediment clasts together with the absence of debris traces upstream from the landslide site ruled out the possibility of a glacial lake outburst flood. The disaster was a result of landslide damming triggered by precipitation and stream undercutting and sudden bursting.