How is climate change affecting flood risk?
- Louisa
- Oct 25, 2019
- 2 min read
Updated: Jan 10, 2020
I came across a great tool this week from Carbon Brief, which maps scientific papers assessing the link between extreme weather events and climate change. It's a fantastic resource for nosing around the most recent research related to extreme event attribution (assessing whether anthropogenic climate change made an extreme weather event more likely or more severe).
The IPCC identifies no clear global trend of changes to the frequency or magnitude of flooding during the twentieth century. However, there is evidence that the frequency of extreme precipitation events has increased (with regional variations), and the increase is projected to increase globally. But what can we say about individual extreme weather events?
Attribution is a relatively new science, and attribution of flooding events is a trickier prospect that say, heat waves. This is because so many factors affect flooding, ranging from atmospheric dynamics and storm paths (more challenging to link to climate change) the amount of moisture in the atmosphere (sometimes less challenging), while other factors such as land use change and river management also affect the location and severity of floods.
Most of the studies on the tool have come out since the last IPCC report in 2013. Of the 51 studies related to extreme rainfall or flooding, 68% indicate that the events have some link to anthropogenic climate change. For example, one paper examines the extreme rainfall in South China in 2017, and finds that the risk of a similar event has doubled (from 0.6% to 1.2%) as a result of climate change.
These papers are all framed slightly differently, and there are many other factors that make disentangling natural climate variability from climate change-driven extremes more complicated. Nonetheless, it does appear that climate change is affecting the pattern of flood hazards, although we still don't have a complete understanding of how. As we have seen though, a change in hazard is just one driver of flood risk; what about vulnerability and exposure?
Climate change can certainly drive changes in vulnerability and exposure: for example, changing rainfall patterns and degraded ecosystems may cause people to abandon agriculture and move to cities, where they may settle in locations which are more exposed to floods, in poor-quality buildings which may make them more vulnerable.
However, future increases in economic damages are more likely to be linked to other factors. A 2016 report predicted a 5-fold increase in flood losses in Europe by 2050, but only 20% of this was due to changes in climate; by far the majority was due to increased building on flood-exposed wetlands. But how land use choices affect flood risk is something for another post.
Very interesting blog, thank you for your work.
I thought this was a particularly interesting and valid point:
“Climate change can certainly drive changes in vulnerability and exposure: for example, more droughts may cause people to abandon agriculture and move to cities, where they may settle in locations which are more exposed to floods, in poor-quality buildings which may make them more vulnerable.”
Indeed, when “climate vulnerable” farmers move to cities they do so because they are highly vulnerable, and perhaps don’t see another solution (e.g. traditional farmers in the Sahel). This could be a coping mechanism, especially for younger generations.
But as you point out, cities will provide other challenges and new risks.
Is moving to cities a good…
Really interesting to read! I hadn't thought about the links between climate change and 'vulnerability and exposure', as you put it; really shines a light on how climate change is already here, affecting people, and yet we are inexplicably slow to act on it.
Great question! So Italy and Hungary are two countries identified in the EEA report as having the highest current exposure (in Italy it's 11% of the population and Hungary 18% living in flood plains). It doesn't go into detail about the current building trends in individual countries, but in the UK in 2016-17, close to 10% of new houses were built in flood risk zones. Most of the increase in losses predicted in the EEA report is attributed to the the increasing economic value of assets in the flood plain: some of this is attributable to new construction, some to changing land use - I'll edit the post to clarify!
"by far the majority was due to increased building on flood-exposed wetlands"-- any chance you know which countries are utilizing wetlands for building?