Water Safe Cities: assessing the global impacts of flooding & drought at city level

C40 Cities
June 2020 – July 2021

In the current state of the climate crisis, cities face significant and increasing climate risks. The majority of these risks are due to changes in both our global and local water cycles. Whether it concerns extreme precipitation resulting in urban flooding, coastal inundation from rising seas and stronger storms, or too little water resulting in shortages and drought: no city in the world is immune to these climatic changes. Together with the Institute for Environmental Studies (IVM), we quantify the risk of flooding and droughts for 97 megacities around the world in the ‘Water Safe Cities’ project.

What does the project entail?
The analysis covers the current and the future (2050) situation, using different climate and socioeconomic scenarios. The risk analysis helps to shed light on the future we don’t want for these 97 cities worldwide. However, this research also includes the next step: offering a meaningful perspective. This means we first assess the future we don’t want: a future in which no adaptation measures are taken. After that, we present a first glimpse of how the risks of drought and inland flooding can be managed, offering a perspective of a future that we do want.

What is the goal of the project?
In 2018, C40 launched the project ‘The Future We Don’t Want’ (FWDW). The FWDW research showed that by 2050, over 570 low-lying coastal cities will face projected sea level rise by at least 0.5 meters, putting over 800 million people at risk from the impacts of rising seas and storm surges. This research analysed how different climate hazards will affect cities across the globe by 2050 including extreme heat, poverty, sea-level rise and its impact on energy supply, food security, and water availability. However, the research did not cover inland flooding and drought impacts. Neither did it assess the economic and social risks of these hazards on cities. The Water Safe Cities project aims to fill this gap.

How do we work?
Flood and drought risk are quantified following the common definition of risk, where risk is a function of hazard, exposure, and vulnerability. For fluvial flooding, we use a state-of-the-art global flood model, while taking into account future socio-economic scenarios based on land use projections from a model developed by the Netherlands Environmental Assessment Agency. Due to data limitations, we assess pluvial flooding by using the probability of extreme precipitation events as a proxy. Drought is measured by estimating the annual water deficits for urban water supply and agricultural areas. Furthermore, risks are monetized in USD for all but pluvial flooding.

More information
Would you like to know more about this project? Please contact Felix van Veldhoven.









Source background image: Henk de Boer (www.henkdeboer.nl)