Using InSAR to detect coastal urban subsidence around the world

Our InSAR results indicate that land is subsiding faster than sea-level is rising in many coastal cities throughout the world. If subsidence continues at recent rates, these cities will be challenged by flooding much sooner than projected by sea-level-rise models. Subsidence rate is highly variable in space and time owing to multiple processes. On a global scale, knowledge of coastal subsidence rates is still spatially and temporally limited. With its unprecedented global coverage and high spatial-temporal resolution, Sentinel-1A/B provides the best tool to monitor coastal subsidence on a global scale. We measured subsidence rates in over 100 coastal cities around the world between 2015-2020 using the PS-InSAR method and Sentinel-1 data. The most rapid subsidence is occurred in developing countries in southeast Asia, where population and water demand will continue to grow. Even in developed countries (North America and Europe), parts of many cities appear to be sinking faster than sea level rise. Continued monitoring and policy intervention are required to reduce subsidence rates and minimize their consequences.