E-Rise: Earliest detection of sea-level rise accelerations to inform lead time to upgrade/replace coastal flood defense infrastructure.

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 planning and implementation of schemes. For example, plans for building the Thames Barrier were started 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 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 (Environment Agency, EDF Energy, 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.

The project will last 1 year and cost (80% FEC) £118,500.

Key words: sea level acceleration, lead times, defence upgrades, Thames Barrier

The impacts of this proposed project will be significant, influencing the monitoring procedures, the planning, and the management decisions of our three project partners (the Environment Agency, EDF Energy and HR Wallingford) and potentially wider stakeholder groups in the UK and internationally (e.g. iSTORM a network of storm surge barrier managers from across Europe). Our outputs will: (1) provide estimates (with uncertainty) of lead times for upgrading/replacing defence infrastructure, for a wide range of projections; and (2) facilitate better methods for monitoring sea-level accelerations. The former will improve management planning and both will allow our partners to make more effective and confident decisions, regarding when to make a change to a new adaptive pathway. Increased confidence in the trajectory of sea level rise will result in direct savings to the public purse, because: (1) it helps to ensure abortive action does not take place or over engineering of the solution, should future sea level rise turn out to be different; and, (2) it allows our partners to defer investment in to the future with confidence. This proposed work will directly contribute to address the recommendations identified by the Environment Agency in their 5-year review of the Thames Estuary 2100 plan. Outputs from our proposed study will thus feed into their more detailed 10-year review that is currently being undertaken. We expect the results to influence their current monitoring procedures and planning decisions relating to lead times, thus aiding major future decisions to move to alternative pathways (such as a new barrier) when necessary. Outcomes from this project will also influence the planning and investment decisions of our other project partners, EDF Energy, in relation to nuclear industry operations/safety measures, and HR Wallingford, who provide guidance to a wide range of clients on coastal infrastructure. As outlined in their strong support letter, EDF Energy highlight that the proposed outputs from this project are very relevant and would represents a step forward in their current practice.

The related issues of lead times and acceleration detection affect the planning and investment decisions for all coastal infrastructure and are a pre-requisite to any effective adaptively managed approach. Hence, the deliverables (i.e. the toolbox), and insight obtained from considering the case study (the Thames Barrier), have wider benefits. Since its introduction in the Thames Estuary 2100 Project, the adaptive pathways approach for managing flooding risk has been implemented in many other management plans, from large scale schemes to protect New York, through to local council schemes to protect small towns. Southampton City Council for example has implemented an approach by which new defences will be built with the capacity to be raised higher, if larger sea level rises are apparent. Yarmouth on the Isle of Wight, have also started to consider adaptive pathways approaches. The outputs from our proposed project will be made freely available at the end, with guidance, for wider use in projects like these. In the future the toolbox could be easily extended to other countries, hence there is potential for international impact.

Collectively, we have considerable experience of carrying out projects that have achieved impact. Our work on high-end sea-level rise scenarios and coastal flooding has been used to develop scenarios of extreme sea levels with DEFRA and the Health and Safety Executive and was used to brief MP's ahead of their debate on coastal flood risk on 7th July 2015. In the Sea Level SpaceWatch project we created a prototype service to support national flood defence planning with improved observations.