Characteristics of some rainfall-induced landslides on natural slopes, Lantau Island, Hong Kong

The north part of Lantau Island is undergoing rapid development following construction of the new airport at Chek Lap Kok. This development, primarily on reclaimed land, is adjacent to a range of steeply sloping hills that experience levels of annual rain in excess of 2500 mm. Rainfall induced landslides on this steeply sloping natural terrain are potential hazards to developments down slope. Landslides on these natural slopes resulting from two major rainstorms in 1992 and 1993 were studied to determine their characteristics and define the geomorphological factors influencing their debris trails. These data were compared with the aerial photographic record of landslide scars within the same catchment over the period 1945-1995 to determine the potential hazard from natural terrain landslides to downslope development. The limited data set indicates that channelized debris flows which produce long debris trails pose the greatest hazard potential to downslope development. Factors influencing debris flow paths and deposition zones were assessed from a geomorphological study of the catchment to define criteria for preliminary hazard zoning of downslope developments.