TerraSAR-X data in cut slope soil stability monitoring in Malaysia

Landslides in Malaysia, and other tropical countries where heavy monsoon rains are common, form a risk to people, buildings, and roads. In particular, steep slopes that have been cut to accommodate road lines are prone to landslides. The objective of the study was to develop algorithms and methods that can be used to alert on increased risk of landslides through detecting small signs of slope instability with synthetic aperture radar (SAR) image analysis. A time series of 19 scenes from the TerraSAR-X satellite was analyzed in study site Gunung Pass. Amplitude image analysis and interferometric techniques were applied to study soil movements. Two terrace fragments were measured to have slid 2.5 and 4.9 m in two amplitude images. The phase of topography-flattened coherence images was used to map small movements in a slope-failure area. The highest movement that was detected with interferometric techniques was 1.71 cm while the corresponding movement in ground data was 2.65 cm. High soil movements (over 16 cm) in the slope failure area prevented the use of phase data because fringes disappeared.