Recommending regional rainfall threshold values for early warning of landslides in the Asian region

Abstract

Regional landslide hazard prediction and warning are still difficult targets to be achieved and a hot topic in the research of landslide hazards. It is necessary to investigate the possibility of interpreting landslide events in terms of the rainfall patterns immediately preceding the slide event. This can be furtherer enhanced by taking the litholoical conditions in to account. Rainfall threshold values vary from region to region due to references in exciting soil characteristics and climatologicall patterns in different areas This paper addresses the needs mentioned above and it includes the data and methods for recommending threshold values adopted by countries, such as Bhutan, Bangladesh, China India, Indonesia, Nepal, Pakistan, Philippines, Sri Lanka, Thailand and Vietnam. A new approach is proposed considering normalized cumulative rainfall from 6 days beyond a certain landslide till the day of occurrence. Data from several countries such as Sri Lanka. India etc have shown very promising outputs as per the application of the proposed methodology. However, it is clearly evident that the extreme rainfalls in a shorter duration could trigger disastrous landslides. This is confirmed by the data from countries such as Nepal, Bangladesh, etc when the rainfall collected 3 days preceding the event till the landslide occurrences is considered.