‘Fire-Floods’: The New Era of California Weather Disasters
California’s struggle to fight increasing wildfires has led to a new stage in natural disasters – what experts are calling the “fire-flood” era, a destructive combination that will have a major impact on the state and the surrounding region.
Here’s how it came to be: fall fire season bakes the soil surface of millions of acres of hillsides, essentially making them non-absorbent. Then come the heavy winter rains, which can’t be absorbed by the soil, instead rolling downhill as a mud/ash mix that also carries boulders and trees.
Don’t confuse them with mudslides, though. While mudslides occur when a hill becomes so saturated that the subsoil begins to slide, debris flows take the top layer of soil and run like flash floods that collect massive amounts of debris. As United States Geological Survey hydrologist Jason Kean told the Sacramento Bee:
A debris flow is a flood on steroids…You add rocks, boulders and other objects. That weight, it is lethal. You can’t block it with a sandbag. You can’t outrun a debris flow. You need to get out of the way.”
These debris flows can run for miles, swamping highways and destroying gas lines and buildings in their path. These conditions can last for several years after a fire. Santa Barbara County is still at risk after the 2017 wildfires, for instance, and Southern California is at a more acute risk because of the steep canyon environment.
The conditions in California are giving emergency response professionals a harsh look at extreme weather events they’ll have to develop strategies to prepare for, from concrete strategies like developing stronger warning systems to social concerns like combating evacuation fatigue among residents and promoting disaster preparedness planning.