Early this year, Chile’s Atacama desert — the driest desert in the world — experienced an extremely rare rainfall, which resulted in flooding that left six people dead. Defined by their aridity, rainfalls are rare in deserts. Sometimes, however, uncommon meteorological circumstances line up perfectly, causing extreme flooding.
Flooding is the most deadly weather threat to humans, and it only takes a small amount of water to trigger one in a dry area. Desert sand does not easily absorb water, and many areas may only see a couple of inches of rainfall over multiple years. Therefore, heavy rains and irregular storms can trigger flash floods, which often follow the paths of dry stream channels. According to the U.S. Geological Survey, more people drown in deserts than die of thirst.
As flash floods often occur within two hours after the start of high intensity rainfall, there is often little time to prepare. Canyons and stream beds are especially dangerous, and rain running down steep terrain can result in mud slides. Those living in highly populated, high desert climate areas are also at elevated risk of flooding as buildings and roads further limit the amount of rain the ground can absorb.
Desert flooding may have other interesting results besides destruction. After a storm brought less than 1 inch of rain water on Southern California’s Death Valley National Park earlier this year, visitors were shocked to find a 10-mile-long shallow lake in the park. The rain water accounted for about one-third of the total annual precipitation for the area, which is the hottest and driest spot in North America. While this rainfall arrived too late in the season, similar events have triggered exceptionally large yields of desert flowers.
In addition to other sources, 24/7 Wall St. used data from the Dartmouth Flood Observatory to determine the beginning and end dates of the floods in question.