'Hard' protection, like dikes and seawalls, can reduce the risk of flooding for several metres of SLR in some coastal C&S. These are most cost effective for densely populated cities and some islands, but may be unaffordable for poorer regions. Although these measures reduce the likelihood of coastal flooding, residual risk remains, and hard protection typically has negative consequences for natural systems. In low-lying protected coastal zones, draining river and excess water will increasingly be hampered, eventually requiring pumping or transferring to alternative strategies.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report