Rainfall-induced landslides in Singapore

Minor, shallow landslides have occurred frequently on the island of Singapore. However, very few major landslides (greater than 10 m in height) have occurred. Slope failures in the sedimentary Jurong and granitic Bukit Timah formations have occurred largely on slopes with angles greater than or equal to 27 degrees. It is clear that rainfall has been the dominant triggering event for landslides in Singapore. Observations of past landslide events suggest that a total rainfall of 100 mm within a six-day period is sufficient for minor landslides to take place. The equivalent condition for major landslides would appear to be 320 mm within 16 days but this is based on very limited data.