PROTECT webinar Coastal risks and adaptation: insights on subsidence and vertical land motion

Coastal subsidence and vertical land motion science to support climate change risk assessment by Robert J. Nicholls et al.
An understanding of vertical land motion (VLM) is critical to analyse the full risks and adaptation needs of climate-induced sea-level rise. People and the economy are preferentially located on subsiding coasts such as river deltas and coastal plains with fertile but also compressible subsurface sediments. Hence, the burden of relative sea-level rise is higher than climate-induced factors alone and in some densely-populated locations subsidence dominates over climate effects. Unlike in climate change, VLM scientists work in relative isolation, and VLM processes are complex and diverse in time and space. Fortunately, VLM science is also undergoing a revolution in terms of observations, and simulation of specific VLM contributions. This provides a basis for improved collaboration and understanding of relative sea-level change. In turn, this supports coastal risk assessment and adaptation, including innovative approaches such as subsidence mitigation and managed sedimentation to raise land levels.
Assessing current Coastal Subsidence at continental scale: insights from Europe using the European Ground Motion Service by Thiéblemont et al.
Land subsidence increases the risk of flooding in low-lying coastal zones by amplifying relative sea-level rise. In this study, we assess for the first time current coastal land subsidence at the scale of Europe using the new Copernicus European Ground Motion Service (EGMS) that was released in 2022. Our results suggest that nearly half of the low-lying coastal areas in Europe are currently subsiding at a rate faster than 1 mm/yr on average. We find that coastal subsidence is higher on average in areas hosting more people, urban centers and critical infrastructure. This raises concerns that coastal subsidence, and therefore relative sea-level rise, tends to be underestimated in Europe and presumably in many other regions around the world. Our study demonstrates that emerging continental-scale land motion services such as EGMS are useful to better characterize the issue and anticipate coastal risks and adaptation accordingly.