How did London build climate resilience against sea level rise through adaptation pathways?

Written by Ismail Weiliang and Liesl Keam, Principal Consultant in Climate Resilience for International Development, UK

23 MAY 2022



The Climatebender


Principal Consultant for Climate Resilience

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Is it that urgent?

Building climate resilience requires action on two fronts: mitigation and adaptation. Carbon mitigation (i.e. mitigating carbon emissions) can reduce the rate of global atmospheric temperature rise, and eventually even reverse it. However, system lags mean that this could take decades. Chronic and acute events are already happening (i.e. heatwaves, droughts, floods, sea level rise). Hence, adaptation measures are needed now to improve climate resilience and prepare for unavoidable present and future impacts. Uncertainty in climate data, and system complexity makes knowing exactly what to do difficult. So how do we adapt?


Quick Take:

  • Adaptation is needed now to  improve climate resilience and prepare for unavoidable present and future impacts.

Managing uncertainty

Climate projections, whilst very useful, can’t provide absolute certainty about the future. Yes we need to make high value and long lasting decisions in this environment of uncertainty. To reduce uncertainty, we adapt through adaptation pathways. Adaptation pathways are sequences of actions implemented progressively and dependent on future dynamics. Short term measures are implemented now while longer term measures depend on certain conditions. Usually presented as a route map or decisions tree, a pathways approach to adaptation planning is about having flexibility to keep options open, managing uncertainty and avoiding mal-adaptation (unintended negative outcomes) and lock-in. A key characteristic of adaptation pathways is that the triggers for the decision points are scaled against a climate variable, such as sea-level rise, not time. Therefore, the pathway is independent of time, removing a large source of uncertainty - the timing of sea-level rise. 

(Source: Reisinger 2014)


Quick Take:

  • The real value of adaptation pathways is in helping decision makers find a way through the uncertainty around climate impacts which can be debilitating for investment decisions.

Adapting to sea level rise in London

London’s flood defences centre around the Thames Barrier which can be raised to defend the city from flood during storm surge events.

(Source: Scientech Info, 2015)

The Thames Barrier took 30 years from the decision to build through to operation. Hence, we acknowledge that while not all decisions can be made now, they can be planned, prioritised and prepared for. Planners look at future flood defences under climate change. In London they laid out a decision pathway up to the year 2100 which considers a number of future climate and sea-level rise scenarios and alternative adaptation options. The pathway identifies the future points at which investment becomes necessary in the light of evolving climate change and sea-level rise which ensures that any new scientific and technological understanding can be incorporated to the extent that is possible.

(Source: CoastAdapt 2017, (modified from HM Treasury and DEFRA 2009, and Reeder and Ranger 2011).


Quick Take:

  • Not all decisions can be made now but they can be planned, prioritised and prepared for.

Value delivered

Adaptation pathways reduce unnecessary expenditure, buys time to plan and reduces the pressure of making decisions now. It prevents organisations from being locked into actions that may not be the best solutions long-term. Rather than determining a final outcome or decision at an early stage, decision makers are able to build a strategy that will follow changing circumstances over time. It reduces uncertainty by using events not time as decision points. However, due to graphical nature and complexity of decision points and triggers, it can be challenging to involve a high level of detail in adaptation pathways. Adaptation action plans can be used in parallel to support in this aspect, capturing, engineering options, capacity, technical skill or institutional policy changes required.

(Source: Siebentritt et al. 2014)


Quick Take:

  • Ultimately reducing OPEX and CAPEX, adaptation pathways provide a framework to plan decisions with confidence in this climate uncertainty.

  • Adaptation action plans can be used in parallel to deliver holistic adaptation with a higher level of detail.

Towards a Common Goal

The process of developing adaptation pathways (shown below) delivers excellent outcomes especially in multi-stakeholders contexts with different vested interests and drivers. It is a useful tool in aligning various stakeholders along a common pathway and process in delivering the project and making investment decisions.

Steps to develop climate change adaptation pathways aligned to British Standards for Adaptation to climate change, Using adaptation pathways for decision making, Guide. (source: BS 8631, 2021)


Quick Take:

  • In developing adaptation pathways, the process facilitates alignment of various stakeholders around a common pathway and process in delivering the project.


Liesl Keam is passionate about working alongside decision makers and governments for climate solutions. Specialising in climate change resilience and adaptation, low emissions development, sector strategy, policy and gender nexus. She has led projects across the globe in the Infrastructure, Agriculture, Renewable Energy, Environment, Rural Livelihoods and Food Security sectors for more than 17 years.

Ismail Weiliang is a climate resilience consultant with over half a decade of experience and specialises in flood risk advisory for Asia. His work involves advising governments and development banks on strategies to transform climate risks into resilience. He also founded “The Climatebender” a non-profit organisation that provides humanitarian relief to communities vulnerable to the climate crisis.

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