Flash floods: Why are more of them devastating the world’s driest regions?
Shifting weather, changing settlement patterns and a lack of preparedness mean that dryland areas are most at risk from flooding. Researchers need to focus on data collection, early-warning systems, flood protection and more.
Last year, around two-thirds of Pakistan was affected by widespread flash flooding, with more than 1,500 people killed and around 33 million made homeless. Almost 2,000 people died in flash floods across Africa, and parts of the United Arab Emirates, Iran, Saudi Arabia, Qatar, Oman and Yemen were inundated with water.
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Because parched soils repel water rather than allowing it to soak in, flash floods can be more devastating in drylands than in wetter areas. Surges can result from relatively small amounts of rain, as little as 10 millimetres in one hour. By comparison, floods in wetter regions typically follow more prolonged bouts of rainfall.
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Dryland residents are paying a high price. Our analysis using the Emergency Events Database (EM-DAT; www.emdat.be) shows that, since 2000, such regions experienced less than half (47%) of deadly flash floods globally, yet saw almost three-quarters (74%) of related deaths (see ‘Global flash-flood disasters’). The majority of these floods (87%) and associated deaths (97%) occurred in low- and middle-income countries.
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Assessing the likelihood and consequences of flash floods requires a lot of data. These include: meteorological and hydrological measurements; topographic data and digital elevation models; records of assets and previous losses; and census data. However, most dryland regions lack much of this information, because national governments often don’t recognize its value and many lack the resources to gather it.
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