We need to start preparing for flood disasters now - here's why

As climate change worsens, it’s projected that tropical cyclones – and the floods they cause – will become less frequent but more intense. The consequences of future storms depend on our actions now. If fewer storms mean that our preparation for them becomes slapdash, then disasters will be worse.

We can see this phenomenon at work when people build flood-related structures like dikes, levees and dams. Since they create a barrier between water and floodable areas, people often assume that those areas are safe to build on and that they don’t need to worry about flood risk. Indeed, the structures get rid of many smaller floods. But when large floods inevitably occur and a river or ocean reclaims its territories, devastation is equally inevitable.

The history of New Orleans offers a classic example. Around half of the city currently lies below sea level, and records of city flooding from the Mississippi River date back over a quarter of a millennium. Plus, New Orleans has always been prone to storms, facing Hurricane Betsy in 1965 and Hurricane Camille in 1969.

In July 2004, the Hurricane Pam training exercise for emergency officials demonstrated how ill-prepared the city was for a direct hurricane hit: especially when it came to hospital evacuation, search-and-rescue efforts, debris removal and temporary shelters. Tragically, this scenario was recreated in real life when Hurricane Katrina tore through the city in 2005. Levees breached, evacuation and sheltering systems were chaotic, and people drowned while on the phone awaiting rescue.

Flood-prone cities are often “protected” by flood “defences”, which have served mainly to encourage housing and business development on floodable land such as in London and Singapore. Both cities sit upstream from vast defences which reduce the numbers of small floods, allowing construction of huge financial centres on floodplains.

But when, not if, a flood exceeds a defence’s capabilities, the lack of preparation will be apparent in the ensuing disaster. Warning systems, which are highly capable of issuing accurate flood alerts, exist – but as in this year’s floods in Germany, these won’t be effective without preparing populations for evacuation.

Rather than constructing dams, the Canadian city of Toronto opted to move buildings out of floodplains after Hurricane Hazel slashed a path through the city in 1954, killing at least 81 people.

Instead of rebuilding flood-ravaged residential streets, Toronto turned them into nature reserves to keep buildings out and water in. City planners then integrated the reserves into the expanding city by creating walking and cycling pathways alongside them. Now, these have become recreational and commuting routes, environmental education sites and a haven for wildlife.

When Hurricanes Isabel in 2003 and Sandy in 2012 again transformed Toronto’s watercourses into raging torrents, its floodplains were bare of buildings. Fallen trees littered mud-slicked paths, transportation and power was disrupted. But there was only one fatality. Let’s use this knowledge and wisdom to prepare other towns and cities for handling future floods.