Abstract
During the past 10 years, Timor-Leste has concentrated all its efforts on infrastructure development. However, it has not achieved enough due to unexpected ground deformation in mountainous areas that is seriously affecting road constructions, etc. In order to design roads and other infrastructure under such difficult conditions, it is important to know the present and future ground conditions. Continuous monitoring is a significant methods of detecting ground deformation and providing essential information to realize an effective design. The problem arises of “How can ground deformation be monitored in extensive areas, which are generally located in mountain areas that are difficult to access?” Differential Interferometry Synthetic Aperture Radar (DInSAR) has recently been applied to monitor displacement in extensive areas. In addition, Unmanned Aerial Vehicle (UAV) photogrammetry is useful for detecting the deformation in detail. Both methods are advantageous in that they do not require any sensors. Therefore, the combination of DInSAR and UAV photogrammetry is one of the solutions for monitoring the ground deformation in Timor-Leste. In this paper, DInSAR and UAV photogrammetry are applied to unstable ground in the Bobonaro region of Timor-Leste to find the recent ground deformation, since 2007, due to earthquakes and hard rainfall events. It is found that DInSAR is useful for screening usual and unusual ground behavior and that UAV photogrammetry is flexible to use and can detect displacements with cm accuracy after the DInSAR screening.
Highlights
After gaining independence on 20 May 2002, Timor-Leste’s policies have been focused on alleviating poverty, addressing the immediate needs of the people, consolidating security and stability, and providing a foundation for the nationhood through the building of state institutions
The ground deformation detected by Small Baseline Subset (SBAS) Differential Interferometry Synthetic Aperture Radar (DInSAR) from both PALSAR1 and PALSAR2 is presented in line of sight (LOS) displacement values and their spatial distribution (Figure 8c,d)
The results showed a good coherence between the latest PALSAR2 LOS displacements were overlayered on the Unmanned Aerial Vehicle (UAV) Digital Elevation Model (DEM)
Summary
After gaining independence on 20 May 2002, Timor-Leste’s policies have been focused on alleviating poverty, addressing the immediate needs of the people, consolidating security and stability, and providing a foundation for the nationhood through the building of state institutions. Following the approval of the Timor-Leste Strategic Development Plan [1], many projects related to infrastructure were started, including the construction of large sections of roads and bridges. The geomorphology and geoenvironment of the country have led to continuous ground deformation, frequent landslides, flash floods, and flooding events during the rainy season, disrupting the land transport system by destroying bridges and washing out roads. This situation has led to direct and indirect negative impacts on the activities and safety of the people, and has delayed ongoing development, wasting resources and time. The data regarding the victims of the various types of geo-disasters revealed that 32 deaths were caused by flash flood and flooding, 11 were caused by windstorms, 10 were caused by wildfires, and 7 were caused by landslides. Problems related to the lack of institutional capacity are making it increasingly difficult to solve these problems [4]
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