Sea level rise and subsidence compound flood risks on the century-old Treasure Island

Treasure Island, a century-old artificial landmass in San Francisco Bay, exemplifies the long-term climate vulnerabilities of reclaimed coastal lands under accelerating sea-level rise. Here we show, using historical records, multi-decadal satellite interferometric synthetic aperture radar, three-dimensional geomechanical modeling, and deep learning projections, that the island is undergoing persistent subsidence (5–11 mm yr−1) and lateral sliding (up to 6 mm yr−1) at its northwest corner. These patterns reflect the complex deformation within a compressible and heterogeneous foundation. Our analysis of land-water interactions projects that sea-level rise is likely to surpass subsidence as the dominant contributor to flood exposure by 2030, with high-emission scenarios indicating significant inland inundation risk by 2050. These findings reveal acute sustainability challenges for Treasure Island’s planned redevelopment and highlight the hidden risks inherent in aging artificial coastlines. While site-specific, this century-scale diagnostics provide a transferable framework for assessing relative sea-level rise and guiding adaptation on reclaimed coasts with similar geotechnical and climatic conditions. Treasure Island is subsiding by 5–11 millimeters per year and sliding by up to 6 millimeters per year, sea-level rise is projected to become the main driver of flood risk by 2030, with substantial inland inundation risk by 2050, according to satellite data, geomechanical modeling, and deep learning.