Originally Posted: January 3, 2022
It’s that time of year on the West Coast when emergency managers prepare for a host of catastrophic weather events — everything from Pineapple Express systems that dump intense rains on the regions to the flooding and landslides that often follow.
Landslides are a near-constant threat to the safety of communities and infrastructure in this part of the U.S. Once an unstable slope gives away, the formed debris flow could travel at a speed exceeding 35 mph, leaving limited time to evacuate people along the flow path and often leading to devastating consequences. Some other landslides, though not evolving into deadly flows, result in constant damages to highways, houses and underground infrastructure.
In January 2005, a portion of a steep slope near La Conchita, Calif., failed and formed a rapid flow, taking approximately 20,000 dump trucks of materials downslope killing 10 and destroying dozens of houses. In March 2014, a hillslope near Oso, Wash., collapsed sending millions of tons of mud and debris to a rural neighborhood within two minutes, killing 43 and devastating a community.
Near Los Angeles the slowly deforming Portuguese Bend landslides progressively slide into the Pacific Ocean, bringing with them hundreds of houses on the slope. On the southern coast of Oregon, the alternately slow and rapid Hooskanaden landslide constantly cracks and deforms Highway 101, costing at least $75,000 for road repair every year.
Across the United States, an average of 25 people are killed and $2 billion dollars worth of properties destroyed by landslides annually. Roughly two-thirds of them occur along the U.S. Coast.
A first step to reduce these devastating and costly landslide damages is to know where they are, before they evolve into an irreversible hazard. This very task was also called out by the recently enacted National Landslide Preparedness Act (Public Law 116-323), which advocates actions to identify landslide risks and reduce losses.
A very good demonstration of such efforts is published in the journal “Landslides.” Funded by NASA Interdisciplinary Research in Earth Science, NASA Earth Surface and
Interior Focus Area and USGS Landslide Hazards Program, the research team, from Southern Methodist University and USGS, utilized approximately 7,000 scenes of satellite radar images from 2007 to 2019, to map 600 large landslides in the Western U.S. Less than 5 percent of them were previously mapped in the USGS landslide inventory. Those landslides ranged in size from the equivalent of seven to 2,400 football fields.
These identified landslides are already in a state of force imbalance. External forces like earthquakes or rainfall could shift some of them into a disaster. Abnormal climate situations powered by climate change could also accelerate how quickly these landslides become catastrophic. READ MORE