Deadly ‘debris flows’ carved destructive California slides
LOS ANGELES — Torrents like the ones that carved deadly and destructive paths through Montecito, California, during a powerful storm early are commonly described as mudslides, but geologists and emergency workers call them debris flows.
Debris flows pose a significant threat when rain falls in the aftermath of wildfires such as the inferno that scorched more than 440 square miles (1,140 square kilometres) in two Southern California counties last month and destroyed and damaged hundreds of homes and other structures. Tuesday’s debris flows killed at least 13 people and injured at least 25.
They happened when water that would have otherwise been absorbed or at least slowed by vegetation instead instantly ran down creeks and other drainage areas, picking up soil, rocks, trees — and potentially growing powerful enough to carry massive boulders and vehicles.
Their speed can exceed 35 mph (56 kph), according to the U.S. Geological Survey.