Protection is effective in the short- to medium-term for many coastal cities, and can be cost effective in the 21st century , but residual risk remains because protection can fail. Even under RCP8.5, technical limits to hard protection may only be reached after 2100 in many regions, but socioeconomic and institutional barriers may be reached before then . With progressive SLR, protection eventually becomes unaffordable and impractical . Combining hard engineering measures with nature-based solutions, spatial planning and early warning systems can help to contain residual risk . Protective works do not prevent salinisation and higher groundwater levels , and can lead to loss of coastal habitat . Hard protective measures also create long-term path dependency as they last for decades and attract new development, locking in impact and exposure as C&S grow, with the expectation of ongoing protection .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report