On March 26, 2004, the gigantic landslide occurred on the caldera wall of Mt Bawakaraeng, Indonesia. This paper quantitatively shows the temporal change in the sediment discharge from the huge amount of the deposit of the landslide through the differentiation of the multi-temporal DEMs obtained by the stereo matching of two optical satellite images. Firstly, the landslide buried the original river channel completely. In the next year, gully erosion dominated on the entire landslide deposit and some part of the gully bed was found to degrade up to 60 m. The total amount of sediment which had discharged from the area of interest was estimated to be 36. 3 million m3. In the second post-event year, such a severe and entire degradation was almost terminated and some part showed a tendency of the river bed aggradations. The total amount of the discharged sediment drastically decreased and was estimated to be 8. 3 million m3.
Geomorphologic characteristics of the Leyte debris avalanche occurred on 17th Feb. 2006 in Philippine was detected using high-resolution satellite imageries. Especially, the shape of hummocks was measured using ALOS PRISM stereo imageries, and was analyzed by GIS compared with the hammocks of Bandai Volcano. As the result, it is clear that the relationship between volume of collapse and size of hummocks between flow distance and long axis direction of hummocks.
This study investigates the potential of geomorphic filters derived from LiDAR 2-m grid DEMs to identify landslide features. The filters, slope and the eigenvalue ratio, were derived from the DEM for 6 landslides as well as two 0. 1 km2 areas where no landslides were identified. Field survey was also conducted to investigate their surface conditions. Results highlighted the importance of filters in characterising landslide features as well as the various stages in their development and activity. The relationships expressed between filter values and landslides are a reflection of the hardness of underlying rocks.
The launch of the Advanced Land Observing Satellite 'Daichi' enabled us to detect the deformation of the land surfaces in detail with its high-resolution synthetic aperture radar sensor. We have observed a number of characteristic patterns reflecting the local surface deformation in an interferogram processed to detect the surface deformation triggered by the Noto Hanto Earthquake in 2007, which indicate the slight movements of landslides accompanied with the seismic motion. We processed an interferogram for Chuetsu-oki Earthquake in 2007 as well, and found several pattaerns suggesting the occurrences of subsidence and lateral flow of the soil. Thus, SAR interferograms can provide important information for monitoring of further development of deformation and planning of countermeasures.
The 2005 Earthquake of Northern Pakistan (Magnitude 7. 6) occurred on 8 October 2005, slope failures were triggered at more than 2, 000 locations. Using a 90-m-resolution digital elevation model (DEM) , the authors determined that most of the slope failures occurred at the hanging walls of the reverse fault and that many large slope failures occurred near the reverse fault. In this paper, we selected 977 slope failures exceeding 250 m2 in area (roughly 15 m x 15 m) that occurred within 4 km from a reverse fault, and we calculated the slope failure orientation using 15-m-resolution DEM derived from TERRA/Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. It was confirmed that at least 30% of those slope failures occurred on slopes facing S or SW. Furthermore, it was confirmed that the slope failure orientation is consistent with the hanging wall-surface displacement (permanent displacement by the seismic faulting) data obtained by Environmental Satellite (ENVISAT) /Synthetic Aperture Radar (SAR) . According to oral accounts from residents recorded by other researchers, most of the surface displacement occurred immediately after the main shock. This suggests that the main factor in the orientation bias of slope failure is the orientation bias of surface displacement.