Managing uncertainty in the appraisal of adaptation options for addressing sea-level rise in London, UK

The Thames Barrier is a movable structure that spans roughly 500 m across the River Thames, east of London. The Barrier was designed to last until 2030 and to provide a high standard of protection (equivalent to a one-in-1,000-year event). The goal of the Thames Estuary 2100 (TE2100) project was to develop a strategic flood risk management plan for London that would be in place until the end of the 21st century. Owing to deep uncertainty surrounding future extreme water levels in the Estuary with climate change and the long-lived nature of the decisions involved, and with high irreversible costs, TE2100 used an adaptation pathways approach. Four potential packages of adaptation actions—referred to as “High-level Options”—were developed by TE2100. Each HLO consists of a pathway through the century that can be adapted to the rate of change of observed sea-level rise. Crucial to the adaptation pathways approach is the need to define “decision points” in advance of a climate change impact taking place (i.e., to identify future times when decision makers will need to choose a more irreversible option, as well as the information needed to inform that decision).

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