Earliest detection of sea level rise accelerations to inform planning and implementation time to upgrade/replace the Thames Barrier

There is strong observational evidence that global mean sea levels are rising and the rate of rise is predicted to accelerate, significantly threatening hundreds of billions of pounds of infrastructure around the UK coast. Substantial upgrades/replacements to coastal defences will therefore be required to maintain existing flood risk management standards. However, this will involve long lead times relating to both planning and implementation of schemes. For example, plans for building the Thames Barrier were started soon after the notorious 1953 North Sea flood, but the Barrier was not operational until 1982 – nearly 30 years later!

Rapid rates of sea-level rise will reduce the lead time available for upgrading/replacing defence infrastructure. Moreover, detecting accelerations in the rate of sea-level rise is not straightforward, due mainly to the considerable inter-annual variability evident in sea level at regional/local scales. Our latest research has shown that it could take years to more than a decade before discernable accelerations are detected. There is therefore an immediate need to: (1) explore how quickly different sea-level accelerations can be detected, and to compare these with the lead times that are necessary for upgrading/replacing different defence infrastructure; and (2) assess whether we could detect sea level accelerations earlier, thereby extending the lead times available for action.

These issues are particular important in relation to the adaptive pathway approach for managing increasing flood risk that was pioneered in the Thames Estuary 2100 (TE2100) project. Although the essence of an adaptive management plan is its ability to adapt when needed, it will only be effective if: (1) a significant acceleration in sea-level rise is detected and then a decision is made in timely manner to move to an alternative pathway; and (2) there is an appropriate lead time to carry out the necessary adaptation. In their first interim review of the TE2100 plan, our project partners the Environment Agency have identified that they need to do much more to: (1) understand how they identify changes in sea level which significantly depart from the assumed projections; and (2) understand the lead times to put in place the flood risk management interventions.

Our proposal will apply previous NERC-funded research and other relevant research to better understand likely lead times for upgrading/replacing coastal defence infrastructure around the UK coast over the 21st century, and assess whether we could detect sea-level accelerations earlier to provide sufficient lead time for action. To do this we will develop an active partner group to discuss the issues, challenges and implications relating to detection of sea-level accelerations and the lead times. We will then develop a toolbox that will allow us to: (1) identify the timings (with uncertainties) at which accelerations in sea-level rise might first be recognized using the best possible combination of in situ and satellite-based data and most appropriate statistical methods; and (2) to estimate the lead times; for a wide range of sea-level projections. As a case study, we will use the toolbox to examine the planning and engineering implementation requirements and their associated lead times for upgrading/replacing the Thames Barrier and associated defences. The toolbox, example outputs and the guidance notes developed will be made freely available via the www.psmsl.org website, for wider use.

The study will be transformative as the outputs will allow our partners (the Environment Agency, EDF Energy and HR Wallingford) and wider stakeholders to: better plan for the future by incorporating information on lead times; better monitor change; and make more effective and confident decisions as to which specific adaptive pathway to follow.