Contemporary relative sea-level rise as a coastal hazard

Abstract

Climate-induced sea-level rise and vertical land movements, including natural and human-induced subsidence in sedimentary coastal lowlands, combine to change relative sea levels around the world’s coasts. Although this affects local rates of sea-level rise, broad-scale assessments of the coastal impacts of subsidence and their implications were lacking until recently. Importantly, coastal inhabitants are preferentially located in subsiding locations. In fact, humans often contribute to substantial  subsidence especially on sedimentary coastal lowlands and deltas due to processes such as groundwater withdrawal. Hence the average coastal resident  experiences a relative sea-level rise substantially exceeding the contribution due to climate change. Several examples will be presented to illustrate this point. Collectively, this indicates that the impacts and adaptation needs due to relative sea-level rise are much higher than reported global sea-level rise measurements would suggest. In addition to climate mitigation and adaptation, subsidence mitigation should also be considered. This could offer substantial and rapid benefits to reduce growth of coastal flood exposure due to relative sea-level rise.

Bio

Robert Nicholls has long experience of analysing long-term coastal problems and solutions from a systems perspective. Much of his work has focused on sea-level rise and climate change, and also the future of populated deltas. He is a longstanding contributor to Intergovernmental Panel for Climate Change (IPCC) assessment process (1992 to 2019). He was formerly Director of the Tyndall Centre for Climate Change Research based at University of East Anglia and Professor of Coastal Engineering at University of Southampton and still works with both institutions.