already experiencing severe compounding impacts, including from sea level rise and climate variability . Coastal cities are disproportionately affected by interacting, cascading and dimate-compounding climate and ocean-driven impacts, in part because of the exposure of multiple assets, economic activities and large populations concentrated in narrow coastal zones , with about a tenth of the world's population and physical assets in the Low Elevation Coastal Zone . Early impacts of accelerating sea level rise have been detected at sheltered or subsiding coasts, manifesting as nuisance and chronic flooding at high tides, water-table salinisation, ecosystem and agricultural transitions, increased erosion and coastal flood damage . Coastal settlements with high inequality, for example a high proportion of informal settlements, as well as deltaic cities prone to land subsidence  and small island states are highly vulnerable and have experienced impacts from severe storms and floods in addition to, or in combination with, those from accelerating sea level rise . Currently, coastal cities already dependent on extensive protective works face the prospects of significantly increasing costs to maintain current protection levels, especially if the local sea level rises to the point that financial and technical limits are reached; systemic changes, such as relocation of millions of people, will be necessary .  
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report