Estimating Rainfall Thresholds for Landslide Occurrence in the Bhutan Himalayas
Estimating Rainfall Thresholds for Landslide Occurrence in the Bhutan Himalayas
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DOI：
10.3390/w11081616
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发表时间：
2019-08-01
期刊：
影响因子：
3.4
通讯作者：
Dorji, Kelzang
中科院分区：
文献类型：
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作者：
Dikshit, Abhirup;Sarkar, Raju;Dorji, Kelzang
多年来，特别是在季风季节，不丹的山体滑坡和相关地质灾害一直对人类生命、财产和道路网络造成巨大损害。确定降雨引发滑坡的阈值是开发预警系统的最有效方法之一。这些阈值是使用各种降雨参数确定的，并已成功计算出世界不同地区不同规模的阈值。这些阈值可用于预测山体滑坡事件，这有助于向市政当局发出警报。目前缺乏关于确定不丹滑坡事件特征的降雨阈值的综合研究。本文重点定义不丹西南部 Chukha Dzongkhag 的事件降雨持续时间阈值。选择该研究区的原因是，季风期间沿途经该国的彭措林-廷布高速公路山体滑坡频率增加，该高速公路是该国与世界其他地区的主要贸易路线。本阈值方法围绕使用幂律方程来确定事件降雨持续时间阈值。该阈值是利用 2004-2014 年可用降雨和山体滑坡数据确定的。计算出的阈值关系适合导致滑坡的降雨条件的下限，并以对数坐标绘制。结果表明，持续24小时、累计降雨量53毫米的降雨事件即可引发山体滑坡。随后，还分析了 3-30 天的前期降雨结果，以根据累积事件降雨了解其对滑坡发生率的影响。还观察到，该地区发生滑坡需要至少 10 天前降雨量 88 毫米和 20 天前降雨量 142 毫米。通过提供每小时降雨量数据和添加更多滑坡数据，可以改进所提出的阈值。这些也可以用作早期预警系统，特别是在彭措林-廷布高速公路沿线，以防止任何贸易中断。
Consistently over the years, particularly during monsoon seasons, landslides and related geohazards in Bhutan are causing enormous damage to human lives, property, and road networks. The determination of thresholds for rainfall triggered landslides is one of the most effective methods to develop an early warning system. Such thresholds are determined using a variety of rainfall parameters and have been successfully calculated for various regions of the world at different scales. Such thresholds can be used to forecast landslide events which could help in issuing an alert to civic authorities. A comprehensive study on the determination of rainfall thresholds characterizing landslide events for Bhutan is lacking. This paper focuses on defining event rainfall-duration thresholds for Chukha Dzongkhag, situated in south-west Bhutan. The study area is chosen due to the increase in frequency of landslides during monsoon along Phuentsholing-Thimphu highway, which passes through it and this highway is a major trade route of the country with the rest of the world. The present threshold method revolves around the use of a power law equation to determine event rainfall-duration thresholds. The thresholds have been established using available rainfall and landslide data for 2004-2014. The calculated threshold relationship is fitted to the lower boundary of the rainfall conditions leading to landslides and plotted in logarithmic coordinates. The results show that a rainfall event of 24 h with a cumulated rainfall of 53 mm can cause landslides. Later on, the outcome of antecedent rainfall varying from 3-30 days was also analysed to understand its effect on landslide incidences based on cumulative event rainfall. It is also observed that a minimum 10-day antecedent rainfall of 88 mm and a 20-day antecedent rainfall of 142 mm is required for landslide occurrence in the area. The thresholds presented can be improved with the availability of hourly rainfall data and the addition of more landslide data. These can also be used as an early warning system especially along the Phuentsholing-Thimphu Highway to prevent any disruptions of trade.