Synergistic Impacts of Land Deformation and Rapid Socio-Ecological Changes on Disaster Risk in Indonesian Alluvial Plains Using Multiple Satellite Datasets

Unique, small-scale tectonic and geological systems are occasionally vulnerable to natural hazards. Although the combination of such systems with rapid socio-ecological change can enhance the risk of disasters, such synergistic impacts have not been well studied. The primary goal of this study was to investigate the potential synergistic impact of land deformation and rapid socio-ecological changes on disaster risk in lowland alluvial regions of a collision zone in the Gorontalo Regency of Gorontalo Province, Indonesia. In this region, socio-ecological changes such as urbanization and rapid lake shrinkage are significant. Frequent occurrence of flood hazards threatens local livelihood. Differential interferometric synthetic aperture radar analysis of Sentinel-1 C-band data from April 2020 to April 2023 was applied to assess land deformation. Thereafter, supervised classification of moderate and high spatiotemporal resolution optical satellite time series was used to assess the relationship between land deformation and built-up area. The findings revealed both significant land deformation and rapid socio-ecological changes. Vertical deformation rates were as high as ~6 cm/year and were primarily attributable to tectonic activity; they were particularly apparent in rapidly developing and highly populated residential areas. Rapid shrinkage of a lake resulted from the local geological system and socioeconomic changes in the region, which together possibly exacerbated the hazard risk because of their effects on land deformation. These results indicate the potential danger to both infrastructure and human inhabitants at a regional level due to the synergistic effects of natural processes and socio-ecological changes. The study design and data that were used facilitated a comprehensive assessment of the potential impacts on disaster risk. These findings are expected to be integrated into locally specific hazard (e.g., flood inundation and ground fissuring) risk mitigation and management strategies.