Recent images of the devastating flash floods caused by Storm Daniel in Greece hit close to home literally and figuratively. As a Greek who has completed a PhD and worked for the past eight years on flash floods, the scenes unfolding across my homeland are painfully real: a stark reminder of the broader environmental challenges we face both on a local and a global scale.
These unprecedented flash floods were triggered by rainfall from the arrival of Storm Daniel on Monday September 4 which also affected Turkey and Bulgaria. The following day, in the village of Zagora, a record-breaking 754mm of rain fell in just 18 hours, leaving parts of the region of Thessaly in crisis and unable to respond.
To put this in perspective, London gets about 585mm of rain over the course of a year while Thessaly gets 495mm, meaning that on Tuesday, about 1.5 years’ worth of rain fell in 18 hours. Imagine the most torrential rain you have ever experienced, perhaps a cloudburst lasting 20 minutes or so. Now imagine it raining that hard but without pause for an entire day.
Flash flooding is short in duration but extremely intense, and typically happens within six hours of heavy rainfall. Unlike regular floods, which develop more slowly and can be predicted in advance, flash floods catch people off guard due to their rapid onset and are rarely recorded in the field.
Across the three affected countries the floods have killed at least 18 people, with many others seeking refuge on their rooftops. There are ongoing power and water outages, infrastructure has been damaged, houses and even entire villages have been completely submerged.