Coastal Flooding and Structure Stability

Recent coastal flooding events such as those induced by the Hayian cyclone in 2013 in the Philippines highlight the vulnerability of coastal zones to flooding. The risk associated with such events is likely to increase in the future for two reasons: first, many coastal zones worldwide are either already urbanized or rapidly developing; second, sea level is rising relative to land elevation in most locations due to anthropogenic climate change and coastal subsidence. In this chapter, we review how remote sensing information can support coastal flooding hazard assessments, including the possibility of defense failure due to existing ground instabilities that weaken coastal infrastructure. Interferometric Synthetic Aperture Radar (InSAR) is a key remote sensing method, providing regional maps of often poorly modeled or even unknown zones of coastal subsidence. Simultaneously, InSAR allows identifying the instability of single structures (e.g., embankments, buildings, dikes) developed for coastal defense of areas prone to flooding. Other remote sensing methods are also useful to support the process of hazard mapping, including digital elevation models and satellite altimetry measurements. We summarize how remote sensing information is currently used by risks and adaptation practitioners concerned with coastal flooding. We argue that one way to maximize the benefits of remote sensing information would be a systematic analysis of coastal flooding hazard mapping workflows to identify information gaps potentially satisfied by remotely sensed data.