The goal of the work has been to assess the factors that led to the series of landslides, which ravaged the District of Kodagu situated in the mountainous Western Ghats, in 2018. The work has been accomplished through field investigations and analysis of field data. While commonly, studies in India lay emphasis on the geological aspects and anthropogenic factors associated with landslides, the present work intended to study in detail the hydrological aspects of the disaster, which wreaked havoc in the region characterised by deep soils, very heavy rainfall and a dense vegetation cover. All the slides of significant magnitude along a 25-km stretch of the Payaswini valley, draining the western slopes of the Madikeri hill range, were identified, and their land characteristics delineated using field surveys and maps. Soil characteristics of the region were determined through tests on samples collected from ten slide sites. Results from tests on texture, density and permeability were used to learn about the part played by subsurface water. Characteristics of rainfall during the year were investigated using field data from the worst affected region. Studies on progress of the Monsoon rain, an analysis of probability of extreme values and establishment of intensity–duration relationships were accomplished. A variable source area watershed model incorporating MODFLOW, the popular ground water flow simulation model, has been applied on a typical micro-catchment in order to study the growth of the saturated zone during rains. It has been inferred from the investigations that an unprecedented combination of extremely wet catchment and a very heavy spell of rainfall, rather than any commonly attributed factor, has been the primary cause of the disaster in the district. It is concluded that it would be a futile exercise working on this natural phenomenon devoid of extensive field studies, because of the uniqueness of the region.

中文翻译：

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对 2018 年印度南部 Kodagu 滑坡的水文方面的洞察

这项工作的目标是评估导致 2018 年席卷西高止山脉的 Kodagu 区发生一系列山体滑坡的因素。这项工作是通过实地调查和实地数据分析完成的。虽然印度的研究通常强调与滑坡相关的地质方面和人为因素，但目前的工作旨在详细研究灾害的水文方面，该灾害对该地区造成了严重破坏茂密的植被覆盖。沿着帕亚斯维尼河谷 25 公里长的所有重大滑坡都被识别出来，这些滑坡排干了马迪凯里山脉的西坡，并使用实地调查和地图描绘了它们的土地特征。该地区的土壤特征是通过对从十个滑坡点采集的样本进行测试确定的。质地、密度和渗透性测试的结果用于了解地下水所起的作用。使用受影响最严重地区的现场数据调查了一年中的降雨特征。完成了季风降雨进程的研究、极值概率分析和强度-持续时间关系的建立。包含流行的地下水流模拟模型 MODFLOW 的可变源区流域模型已应用于典型的微流域，以研究降雨期间饱和带的增长。从调查中推断，极端潮湿的集水区和非常强的降雨量史无前例地结合在一起，而不是任何普遍归因的因素，而是该地区灾难的主要原因。结论是，由于该地区的独特性，如果没有广泛的实地研究，研究这种自然现象将是徒劳的。