How rapid Climate Risk Assessments (CRAs) enabled by publicly available data sources can inform adaptation action in cities around the globe
The Challenge
Cities across the world are beginning to recognize the need to adapt to climate change. But the task can often feel so large, varied and wide-ranging that a common question we hear is: “Well, where do I even begin?”
Empirical knowledge on a variety of climate risks is commonly available, but this data is yet to be harmonized, standardized or validated. With the support of the research community, cities can better understand the climate-induced risks that are prevalent now and which are likely to constitute the main threats in the future. By helping them to break down the complexity of risk into its components of hazard, exposure, vulnerability, and adaptive capacity (see Fig.1), cities will be better equipped to understand and analyze risks. These Climate Risks Assessments (CRAs) should help cities answer various questions, such as:
- “Have extreme hazards become increasingly more extreme and frequent, or have we become increasingly more exposed to these hazards?”
- “Should we actually update our policies on where and how we build?”
- “How can we reduce social vulnerabilities that are a result of socio-economic processes which, most of the time, have little to do with the hazard itself?”
CRAs do not come cheap because they involve detailed studies. One way to help manage the costs of these studies is to start with preliminary assessments that help identify core areas to invest in.
The method and solution
Deltares and R-Cities collaborated to offer precisely this service to cities that are just starting to build their knowledge and capacities. The wealth of digital data – from bio-geophysical to socio-economic – is astonishing. Deltares is capitalizing on these digital resources to mature relevant tools, and through its partnership with R-Cities is testing them around the globe. Deltares has developed a risk assessment workflow for cities, based on its BLUE-EARTH engine, which consists of a chain of fast models (wflow[1], Sfincs[2], FIAT[3]), automatically set up and applied using publicly available global remote-sensing data. Making use of this risk assessment workflow, Deltares can quickly run simulations and assess risks of pluvial, fluvial and coastal flooding and stresses such as prolonged or recurring drought from water deficits.
This methodology was applied in 10 member cities of the Resilient Cities Network. Indicatively, for the City of Surat in India, urban flood hazard and its corresponding flood damage was established (see Fig.2). The damage assessment made use of a variety of social indicators including GDP and GINI coefficient (an indicator of income distribution, population density among others).
In a more indicative manner, the relative risk of drought was estimated for multiple cities around the globe (see Fig.3). The results showed that certain cities share the same relative risk level. The risk level however can be attributed to the variable contribution of each risk component. For this same reason, cities with very similar climate characteristics can have very different risk profiles. This can provide useful insight while planning for adaptation.
Co-design and validation with city experts
Cities are often presented with scientific results, which are rarely put to test by their local experts. In this case, the partnership worked closely with the Chief Resilience Officers of the cities and their respective teams, to validate these results and explore possible decisions that could be taken on the basis of these results. Fig.4 shows how the new approach moves away from top-down scientific knowledge dissemination to actual engagement, co-design, and capacity building.
Model outputs were discussed in bilateral meetings to assess:
- their applicability: Are the areas that are flooded in the model, also flooded in reality? And the vice-versa, are observed floods represented by the models?
- their usefulness: Does the analysis provide new information? Are the results at a resolution that could be useful to decision makers and policy makers?
In most cases, the model results received positive feedback and their usefulness was established. They do not provide answers to all questions, however, they helped cities raise new questions themselves, along the lines of:
- “Do we need a more detailed study in this particular area?”
- “Which measures should we prioritize to reduce risk in this particular area of the city?”
- “What spatial planning policies do we need to reduce our hazard exposure?”
- “How do we reduce our infrastructural and social vulnerability in this particular area?”
Implications
These questions cannot be answered by rapid CRAs alone but they make evident the extent of the cities’ needs for similar assessment tools to kick-start their adaptation work. These discussions also made clear, that the space for solutions goes much beyond technical analysis and engineering structural interventions; it involves thinking in an integrated way about the development of all urban systems (including transport, waste, mobility, energy) and also taking effective non-structural measures.
Call to action
The barriers to entry for cities to have their own CRAs are lower today than ever before. Tools are available and costs are lower. Cities can therefore take advantage of rapid-CRAs, such as this one, so their departments and broader ecosystem of stakeholders can engage with climate risk to build their capacities, strengthen their preparedness and plan for the longer term. When carried out on a global scale, as presented, harmonized rapid CRAs can also serve as a basis for cities to learn from each other: understand what works elsewhere, why it works and how it can be adapted to a new city context. This newly initiated exercise can prove valuable for the 10 participating network cities shaping a new Community of Practice.
Co-Authored by:
Hans Gehrels,
Expert Advisor on Sustainable Urban Water Management, Deltares
Leon Kapetas,
Lead for Programs and Climate Resilience, Resilient Cities Network
Guy van Hemel,
Junior employee, Deltares
Peter Blokland,
Junior employee, Deltares
Additional resources
The results for the cities of Surat (India), Lagos (Nigeria) and Milan (Italy) were discussed at the special session of the “Understanding Risk Asia” conference organized by the World Bank.
Eilander, D., Couasnon, A., Muis, S., Ikeuchi, H., Dullaart, J., Yamazaki, D., Winsemius, H. C., & Ward, P. J. (submitted). Validation of a globally-applicable compound flood hazard modeling framework: A case study in the Sofala region of Mozambique. Natural Hazards and Earth System Sciences Discussions.
Tim Leijnse, Maarten van Ormondt, Kees Nederhoff, Ap van Dongeren, 2021. Modeling compound flooding in coastal systems using a computationally efficient reduced-physics solver: Including fluvial, pluvial, tidal, wind- and wave-driven processes. Coastal Engineering, Volume 163, 2021, 103796, ISSN 0378-3839. https://doi.org/10.1016/j.coastaleng.2020.103796
