International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
5.2 Landslides
Denuded hill slopes (Figs. 5, 6) correlate to areas of disturbed,
possibly burned, vegetation seen in Fig. 3. LANDSAT TM
resolution (30 m) precludes detection of shallow landslides in
NDMIDIR images, however, numerous fresh shallow landslides
are detected in the higher resolution IKONOS FCC image (Fig. 6).
Landlides are identified on the basis of tone (indicating exposed
surfaces) and feature shape. Collectively, these results
demonstrate correlation of landslides to denuded surfaces. This
correlation is significant to establishing a causal and temporal
relationship between episodes of vegetation disturbance and
landsliding.
Figure 4. FCC using IKONOS imagery, Pat Sin Leng Range.
Yellow Insert - see Figure 5. Blue insert — see Figure 6.
Figure 5. FCC highlighting eroded surfaces and disturbed
vegetation (pale colours) south of the Pat Sin Leng escarpment.
The Pat Sin Leng trail that traverses the escarpment crosses the _
image from top left to centre right.
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6. CONCLUSIONS
Using remotely sensed data we are able to depict disturbed
vegetation, denuded hill slopes, and shallow landslides in natural
terrain. Our preliminary work indicates positive correlation
between these factors. This is an important finding in support of
the use of remotely sensed data to predict landslide-prone terrain
in Hong Kong. This work compliments that of the GEO, CED
natural terrain landslide mapping programme by providing
synoptic environmental information (particularly anthropogenic
effects) for large areas of natural terrain, and a means to
investigate specific causative factors.
We have restricted our investigation here to LANDSAT TM and
IKONOS data, but there would appear to be great potential in
using this and other remotely sensed data, such as airborne
radiometrics (Cranfield, 2003, pers. comm.) to map specific
ground conditions including the identification of areas of
alteration and deep weathering that may be additional pre-
disposing factors for landsliding. In the longer-term, such work
will serve to inform relevant sectors of local government of the
potential risks associated with major land development projects.
Figure 6. FCC highlighting shallow landslide scars (e.g. arrowed)
in a denuded area, northern Pat Sin Leng Range. Note the absence
of landslides within the red areas depicting healthy vegetation
cover.
REFERENCES
Bannari, A., Morin, D., Bonn, F., Huete, A. R., 1995. A review of
vegetation indices. Remote Sensing Reviews, 13, pp. 95-120.
Barbosa, P. M., Gregoire, J. M., Pereira, J. M. C., 1999. An
algorithm for extracting burned areas from time series of AVHRR
GAC data applied at a. continental scale. Remote Sensing
Environment, 69, pp. 253-263.
Cannon S.H., 1997. Evaluation of the potential for debris and
hyperconcentrated flows in Capulin Canyon as a result of the 1996
Dome fire, Bandekier National Park Monument, New Mexico.
USGS Open Field Report, pp. 97-136.
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