Recurring landslides in the Western Ghats have become an important concern for authorities, considering the recent disasters that occurred during the 2018 and 2019 monsoons. Wayanad is one of the highly affected districts in Kerala State (India), where landslides have become a threat to lives and properties. Rainfall is the major factor which triggers landslides in this region, and hence, an early warning system could be developed based on empirical rainfall thresholds considering the relationship between rainfall events and their potential to initiate landslides. As an initial step in achieving this goal, a detailed study was conducted to develop a regional scale rainfall threshold for the area using intensity and duration conditions, using the landslides that occurred during the years from 2010 to 2018. Detailed analyses were conducted in order to select the most effective method for choosing a reference rain gauge and rainfall event associated with the occurrence of landslides. The study ponders the effect of the selection of rainfall parameters for this data-sparse region by considering four different approaches. First, a regional scale threshold was defined using the nearest rain gauge. The second approach was achieved by selecting the most extreme rainfall event recorded in the area, irrespective of the location of landslide and rain gauge. Third, the classical definition of intensity was modified from average intensity to peak daily intensity measured by the nearest rain gauge. In the last approach, four different local scale thresholds were defined, exploring the possibility of developing a threshold for a uniform meteo-hydro-geological condition instead of merging the data and developing a regional scale threshold. All developed thresholds were then validated and empirically compared to find the best suited approach for the study area. From the analysis, it was observed that the approach selecting the rain gauge based on the most extreme rainfall parameters performed better than the other approaches. The results are useful in understanding the sensitivity of Intensity–Duration threshold models to some boundary conditions such as rain gauge selection, the intensity definition and the strategy of subdividing the area into independent alert zones. The results were discussed with perspective on a future application in a regional scale Landslide Early Warning System (LEWS) and on further improvements needed for this objective.

中文翻译：

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在估计滑坡发生的强度-持续时间阈值时雨量计和降雨参数的选择：来自 Wayanad（印度）的案例研究

考虑到最近在 2018 年和 2019 年季风期间发生的灾害，西高止山脉反复发生的山体滑坡已成为当局关注的一个重要问题。Wayanad 是喀拉拉邦（印度）受灾最严重的地区之一，山体滑坡已成为对生命和财产的威胁。降雨是引发该地区滑坡的主要因素，因此，考虑降雨事件与其引发滑坡的可能性之间的关系，可以基于经验降雨阈值开发预警系统。作为实现这一目标的第一步，我们进行了详细研究，利用 2010 年至 2018 年期间发生的滑坡，利用强度和持续时间条件为该地区制定了区域尺度降雨阈值。进行了详细分析，以选择最有效的方法来选择与滑坡发生相关的参考雨量计和降雨事件。该研究通过考虑四种不同的方法来思考为该数据稀疏区域选择降雨参数的影响。首先，使用最近的雨量计定义区域尺度阈值。第二种方法是通过选择该地区记录的最极端降雨事件来实现的，而不管滑坡和雨量计的位置。第三，强度的经典定义从平均强度修改为最近的雨量计测量的峰值日强度。在最后一种方法中，定义了四个不同的局部尺度阈值，探索制定统一气象水文地质条件阈值的可能性，而不是合并数据和制定区域尺度阈值。然后对所有开发的阈值进行验证和经验比较，以找到最适合研究领域的方法。从分析中可以看出，基于最极端降雨参数选择雨量计的方法比其他方法表现更好。结果有助于理解强度-持续时间阈值模型对某些边界条件的敏感性，例如雨量计选择、强度定义和将区域细分为独立警报区的策略。