Abstract
Extreme heavy rainfall events in the hilly region pose a great threat to public safety and causes dangerous landslides in the region. Several factors contribute to a landslide and, hence, it is essential to analyze the causes of such related incidents in all possible ways. Though rainfall is the major triggering factor for most of the landslides in the Western Ghats, the long period antecedent moisture level prevailing in the soil of a hilly terrain cannot be ignored. Few of the drought assessing and monitoring indices available in literature can be adopted to predict the degree of wetness from long-term precipitation data of the region. In the present work, three moisture level assessment indices, namely, standardized precipitation index (SPI), China Z-index (CZI), and statistical Z-Score (SZS) index are used to categorize the antecedent moisture level of Coonoor station. Monthly rainfall data for a period of 81 years is used for the study. It is evident from the study that higher level of moisture followed by heavy rainfall triggers medium- to large-scale landslides. Further, from the study it is inferred that an early warning for a landslide can be given once cumulative rainfall exceeds 300 mm during continuous storm periods.
Highlights
Landslides due to rainfall infiltration along the slope of the hilly terrain and cut slopes is one of the important research areas in landslide investigations, for which short-duration rainfall data is essential [1]
Though most of the drought indices are generally used to assess the dryness of a place that leads to different degrees of drought severity, standardized precipitation index (SPI), China Z-index, and statistical Z-score give ranges for moisture level in wet conditions too
In the Coonoor town of and the Nilgiri district are of the Tamilnadu, India, precipitation related of landslides.like
Summary
Landslides due to rainfall infiltration along the slope of the hilly terrain and cut slopes is one of the important research areas in landslide investigations, for which short-duration rainfall data is essential [1]. Though most of the drought indices are generally used to assess the dryness of a place that leads to different degrees of drought severity, SPI, China Z-index, and statistical Z-score give ranges for moisture level in wet conditions too. Kawagoe et al [7] indicated that landslides in Japan are closely associated with its rainfall exceeding threshold values of precipitation It is to be noted from various literatures that cumulative rainfall, antecedent rainfall, rainfall intensity, and rainfall duration are the most commonly investigated rainfall parameters for landslide initiation. Several such events build up moisture in the hill soil, which could be one of the potential triggering factors for landslides
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