APPLICATION OF REMOTE SENSING DATA TO LANDSLIDE 
MAPPING IN HONG KONG 
V. K. Vohora and S. L. Donoghue 
Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, SAR, China 
vijay@hkucc.hku.hk, donoghue@hkucc.hku.hk 
Commission IV, WG IV/6 
KEY WORDS: Landslides, Vegetation, Environment, Multispectral, High resolution, Correlation 
ABSTRACT: 
Rapid encroachment of Hong Kong’s urban areas into natural terrain creates a considerable potential risk from landslides. In recent years, 
considerable effort has been directed towards identifying geological parameters that pre-dispose natural terrains to landsliding and the 
assessments of landslide risk. There has, however, been little investigation of other possible causative factors, specifically, the role of 
vegetation type and disturbance, particularly hill fires, in promoting shallow landsliding. Fire-denuded hill slopes may be subject to more 
frequent landsliding events. Today, much of Hong Kong’s hill slopes are covered in fire-prone grasslands, and hill fires associated with 
cultural festivals are common place. This paper presents an approach to using remote sensing techniques to model areas of disturbed 
vegetation and detect associated shallow landslides in natural terrain. The research uses data from two satellites, LANDSAT TM and 
IKONOS. LANDSAT TM is used to detect disturbed vegetation using visible, near and mid-infrared bands and to obtain vegetation 
indices NDVI and NDMIDIR that indicate plant vigor. IKONOS high resolution multispectral data are used to prepare a color composite 
image to locate shallow landslides, that are correlated to LANDSAT depicted vegetation indices. Results show that this approach can be 
used to correlate landslides to areas of disturbed vegetation. Potentially this work has application in defining landslide prone regions. 
1. INTRODUCTION 
Hong Kong is one of the world’s pre-eminent cities with a present, 
but rapidly expanding population of nearly 7.5 million. Its 
population is mostly nestled on the lowland coastal fringe, giving 
this coastal city one of the highest population densities in the 
developed world. Within a few kilometres of its urban centres is 
an expansive hilly terrain comprising deeply weathered Mesozoic 
granites and volcanics. Steep slopes, deeply weathered profiles, 
and a humid tropical climate predispose this terrain to landsliding 
events. Heavily scarred hillsides are testimony to the rapidity and 
severity of landslides in both natural and man-modified 
landscapes. Increased demand for livable space now sees major 
urban developments and infrastructural projects being located 
nearer to natural terrain hill slopes. Such developments have been 
affected by historical events and are at risk from future events (Ng 
et. al., 2002). Historic landslides have been mapped from aerial 
photographs in order to define landslide risk (Ng er. al., 2002). 
The potential use of digital remotely sensed data to the mapping of 
landslides and determination of temporal associations between 
landsliding events and surface conditions has, however, not 
previously been examined. This paper thus represents a first foray 
into the application of digital remote sensing data to natural terrain 
landslide studies in Hong Kong. 
2. BACKGROUND 
2.1 Natural Terrain Landslides in Hong Kong 
‘Natural’ terrain that covers about 60% of the land area of Hong 
Kong is defined as terrain that has not been substantially modified 
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by human activity but does include areas where grazing, hill fires 
and deforestation have occurred. Much of the natural terrain is 
only marginally stable over large areas with 27,000 landslides 
recorded between 1945 and 1997. The Hong Kong Geological 
Survey, Civil Engineering Department (GEO, CED) has compiled 
a Natural Terrain Landslide Inventory (NTLI) for 1945-2000 from 
high altitude aerial photographs. There is also a Large Landslides 
Database (defined by source areas of >20 m wide) compiled from 
low altitude aerial photographs. 
Ng et. al., (2002) recognize that the NTLI suffers from certain 
limitations (poor aerial photograph resolution, perspective 
distortion, ground shadows and vegetation cover) inherited in the 
coverage due to the quality of the high altitude aerial photographs. 
Ng et. al., (2002) also recognize that for the purpose of an a 
assessment of hazards the NTLI database, needs to be 
supplemented with data on corresponding rainfall history and any 
environmental changes (e.g. anthropogenic effects such as hill 
fires) that have affected the mapped arcas. 
Limitations of the existing natural terrain landslide mapping 
programme potentially can be overcome through application of 
remotely sensed data. Remotely sensed data has many advantages 
over traditional aerial photography for mapping landslides and 
other natural hazards. The capability of remote sensing data to 
provide synoptic information over wide areas is a particular 
advantage (Richards, 1993). From a single, high-resolution 
satellite image in digital format, with multispectral information, a 
range of ground surface features can be identified, classified, and 
mapped directly. By comparison, a large number of aerial 
photographs are required to view a similar area, and tedious image 
rectification (geometric correction) is required before features can