Characterization of rainfall-induced landslides

The northern part of Lantau Island in Hong Kong is undergoing very rapid development following completion of the Hong Kong International Airport at Chek Lap Kok on the island. This development is adjacent to a range of steeply sloping hills that experience levels of annual rainfall in the range of 2000-2400 mm. Rainfall-induced landslides on this steeply sloping natural terrain are therefore potential hazards to property developments downslope. The objective of this study is to characterize the initiation process and the subsequent travel distance of the landslides resulting from recent rainstorms, by integrating aerial photogrammetry with GIS. These landslides, which occurred during the 18 July 1992 and 4-5 November 1993 rainstorms, were interpreted from sequential aerial photographs. Data on these landslides were collected to form a landslide database. Such data, together with information on geology, slope gradient, elevation, slope aspect, slope shape, and vegetation cover were entered into a Geographical Information System (GIS), to determine the geologic and geomorphologic characteristics of the landslide source and to estimate the travel distance of landslide debris. It is demonstrated that this integrated approach of GIS and aerial photogrammetry could serve as an effective means of landslide characterization.