Flooding and storms account for almost three-quarters of weather-related disasters. This past month has seen flooding in Asia and a series of powerful hurricanes in the Atlantic. Extreme events such as these are not caused by climate change — they have occurred throughout history — but previous benchmarks are no longer valid; 1-in-100-year events are happening more often, and those timescales are shortening.

Across India, Bangladesh and Nepal over 40 million people were affected by flooding in late August and early September. Heavy monsoon rains, the worst in 40 years, arrived with little warning and later than the normal peak of the monsoon season. A third of Bangladesh was underwater during the flooding, with around 8 million people affected, whereas India and Nepal had over 30 million and 1.7 million people affected, respectively. Cropland and housing was destroyed, meaning many have lost not only their homes but their livelihoods too. Over 1,200 people died across the region and the risk continues when the waters recede, with increases in mosquito-borne and waterborne diseases as well as food shortages.

Hurricane Harvey caused heavy rainfall in Houston, Texas, where urban expansion and impervious surfaces enhanced flooding. This was the third 1-in-500-year flood that the city has experienced since 1979. The US National Weather service had to add a new colour to their precipitation scale to represent the rainfall from Harvey. The standard of floodplain design needs to be updated to handle events such as these.

Hurricane Irma, a Category 5 storm, raged across the Caribbean and on to Florida. It was the most powerful storm ever recorded in the Atlantic, with the warmer sea surface fuelling the hurricane. Irma was so strong that it was detected by earthquake sensors and maintained winds over 185 miles per hour for 37 hours. Whilst Harvey caused damage through heavy rainfall and associated flooding, Irma brought rainfall accompanied by strong winds and storm surge, changing the coastline of the region. The damage bill is expected to exceed US$100 billion for each of these two hurricanes, and the hurricane season is not yet over.

The recovery efforts from such events can be a time to prepare for the changes ahead, with a shift in thinking needed for resilience planning. The built environment and major infrastructure projects need to consider not only what is needed in the future, but also the interaction with infrastructure that is already in place. The costs of mitigation can be large, but earlier investment can greatly limit both climate change and related expenses from extreme events.