When floods become disasters

Rescue workers in respond to floods in the aftermath of Typhoon Hagibis. Floods become disasters when they overwhelm a community's capacity to cope..Photo: Kim Kyung-Hoon/Reuters

For the first post of the flood blog, I want to talk a bit about what we mean when we talk about floods as disasters, and what that implies for reducing the impact of floods.

Disasters are not natural

What is a disaster? There are many different definitions out there, but let's take for the moment a definition from the Red Cross:

"A disaster is a sudden, calamitous event that seriously disrupts the functioning of a community or society and causes human, material, and economic or environmental losses that exceed the community’s or society’s ability to cope using its own resources." - IFRC

The key idea is the disruption to the community or society: natural hazards like floods only become disasters when they interact with people. A flood hazard may result from natural causes, but who is affected by that flood, and to what extent, is as a result of a wide array of social, economic and political factors. Consequently, we should never talk about "natural disasters", as any disaster is inevitably due to human factors. There are enormous amounts of literature on the social construction of disasters, so let's just emphasise #DisastersAreNotNatural, and put that one to bed.

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The geometry of disaster risk

Who is at risk during a disaster, and why? Disaster risk is often conceptualised as a triangle, encompassing hazards, vulnerability and exposure:

One of the few widely-available depictions of the disaster risk triangle that doesn't look like it was knocked up using MS Word's "draw" function. External factors driving disaster risk include climate change and many socioeconomic factors, of which much more in another post. Source: IPCC, 2014

It's worth exploring these concepts in a bit more detail, since in order to prepare for and respond to floods, we need to tackle multiple facets of risk.

GLOFs in Greenland do not normally qualify as a disaster. They are also quite difficult things to find on Google image search. Photo: Alex Livesey/Getty Images

Hazard:

Floods can have many causes: intense rainfall, storm or tidal surges, an overactive groundwater table, setting off a volcano under a glacier, dam failure, and so on.

For a disaster to occur, a hazard is a necessary, but not a sufficient, condition: while a glacial outburst flood in an uninhabitated part of northeastern Greenland may be fascinating for scientists camped out observing it, it does not qualify as a disaster.

Exposure:

Identifying who or what is exposed to the risk of floods is often fairly straightforward: we know, for example, how many people live in the floodplain of a particular river, and how much infrastructure is related there. Exposure varies depending on the size of the hazard: more people living in the same river basin will be exposed to a larger flood than a smaller one (although more rarely, which will probably affect their perception of the risk).

People often choose to live in flood-exposed areas: it can bring many benefits which offset the potential risks, ranging from a nice view to access to fertile land. What forces drive people to live in areas exposed to flooding, and why, are questions that can be linked to vulnerability.

Much of the city of London lies in the Thames floodplain, and is protected from storm and tidal surges by the Thames Flood Barrier. Flood control infrastructure can reduce disaster risk in the short term and increase it in the long term: the perceived protection encourages people and infrastructure to congregate, increasing the potential exposure and vulnerability if it should fail. Photo: GOV.UK

Vulnerability:

Many factors affect how a flood impacts a certain community or individual: consider how flood control infrastructure, early warnings systems, or ability to evacuate may depend on wealth, or how certain livelihoods (such as agriculture) may be more severely affected than others.

Vulnerability is a concept that has received a lot of criticism: it can be a blunt instrument term that ignores the nuanced relationship people can have with certain hazards; it fails to properly take into account the capacities people have to respond to disasters; and it is highly contextual and subjective. But it's useful to have a term that reminds us that ultimately disasters are a function of deeper socioeconomic processes.

What does this mean for reducing flood risk? For me, it's important to remember that however good your science, disaster risk reduction is ultimately about people. I'm interested in understanding more how we can consider the human factor in flood models - so stay tuned for more of this!