Land subsidence: An under-researched coastal hazard

Abstract

While geocentric (eustatic) sea level rise receives widespread attention in politics and media, relative SLR at the coast, mainly caused by land subsidence, is still comparatively under-researched despite much higher rates. While fast-onset extreme events and geocentric (eustatic) sea level rise receive widespread attention in politics, media, and research, the hazard of land subsidence is still under-researched. Taking into account the high rates of land subsidence (in the annual range of cm compared to mm for geodetic sea level rise and the resulting risk towards coastal flooding, this neglect is unwarranted and even dangerous for coastal disaster risk reduction planning.

This presentation introduced first results from research in Japan as well as a combined natural and social science study in Indonesia to bring subsidence more to the forefront of coastal hazard research; using data from radar altimetry, GNSS controlled tide gauge stations, and InSAR mapping as well as focus-group discussions and a standardized household survey. Our analysis of InSAR, radar altimetry, and corrected tide gauges clearly identifies subsidence as the major coastal threat in our study areas in Indonesia. The InSAR data are integrated into our statistical analysis of household responses towards subsidence. We found, that in contrast to fast-onset events, risk perception is a far lesser determinant of responses towards subsidence than it is for fast-onset events. Hence, our results relativize former assumptions that risk perception and not actual exposure lead to action.