Quantified analysis of the probability of flooding in the Thames estuary under imaginable worst-case sea level rise scenarios

Most studies of the impacts of sea level rise (SLR) have explored scenarios of < 1 m during the 21st century, even though larger rises are possible. This paper takes a different approach and explores and quantifies the likely flood impacts in the Thames estuary for a number of plausible, but unlikely, SLR scenarios. The collapse of the Western Antarctic Ice Sheet (WAIS) could cause global mean sea level to rise by 5-6 m; here a time-scale for such an event of 100 years is assumed to create a worst-case scenario. Combined with the 1 in 1000 storm surge event, this would result in 1000 kW of land being frequently inundated. This area currently contains 1 million properties and their inundation would result in direct damage of at least 97.8 billion at 2003 prices. Smaller SLR scenarios, resulting from a partial collapse of the WAIS over 100 years, also have significant potential impacts, demonstrating the vulnerability of the Thames estuary to SLR. Construction of a new storm surge barrier in the outer Thames estuary is shown to provide greater resilience to unexpectedly high SLR because of the additional large flood storage capacity that the barrier would provide. This analysis has, for the first time, connected mechanisms of abrupt climate change and SLR with hydrodynamic modelling used to quantify impacts. In particular, it is recognized that future management strategies need to be adaptive and robust in order to manage the uncertainty associated with climate change.