The March 2014 landslide in Oso, Washington, about 55 miles northeast of Seattle, became the deadliest landslide event in United States history. Forty-three people died and 49 homes and structures were destroyed.
A 91探花 engineer who analyzed the event鈥檚 aftermath began to investigate the circumstances that can make landslides so deadly. The resulting study shows that certain human actions increase the chance of surviving a devastating event, and suggests simple behavioral changes could save more lives than expensive engineering solutions.
The open-access , published in the October issue of GeoHealth, suggests key actions that range from opening doors and windows to continuing to move and make noise if you do get buried.
鈥淭here are in fact some really simple, cost-effective measures that can be taken that can dramatically improve the likelihood that one will survive a landslide,鈥� said senior author , a 91探花professor of civil and environmental engineering.
Worldwide, landslides cause on average more than 4,000 deaths a year recently, with about 25 to 50 of those deaths occurring each year in the U.S. These events may become more frequent as wildfires fueled by warmer temperatures can leave slopes bare and more vulnerable to slides.
Wartman and a 91探花graduate student compiled and analyzed records of 38 landslides that affected occupied buildings. Most of the data came from the U.S., but it included landslides from around the world for which there were detailed records.
The authors recorded the geologic details of each landslide, as well as the reports from survivors of the events. They used newspaper articles, scientific papers, medical examiner reports and other documents to produce a detailed catalog of fatalities caused by landslides hitting occupied buildings. The events, spanning from 1881 to 2019, included the Oso mudslide and the , as well as events in Bangladesh, the Philippines, China, Malaysia, Australia and New Zealand.
Their analysis showed behavioral factors, such as a having an awareness of local landslide hazards and moving to a higher floor of a building during an event, had the strongest association with survival.
鈥淪imply by being on an upper floor, an individual can increase their odds of survival by up to a factor of twelve. This is a powerful finding that we need to consider when we design the layout and vertical access routes in homes,鈥� said first author , who did the work for his 91探花doctorate in civil and environmental engineering and is now a lecturer in the department.
The researchers found some behaviors, despite being performed by only a small number of people, often save lives. 聽According to their results, those actions are:
Before an event
- Be informed about potential hazards, from hazard maps or other sources
- Talk to people who have experienced these events
- Move areas of high occupancy, such as bedrooms, upstairs or to the downhill side of a building
During an event
- Move away from the threat 鈥� don鈥檛 approach an active landslide
- Escape vertically by moving upstairs or even on countertops to avoid being swept away
- Identify and relocate to interior, ideally unfurnished, areas of a building that offer more protection
- Open downhill doors and windows to let debris escape
After an event
- If caught in landslide debris, continue to move and make noise to alert rescuers
Many things the authors predicted would be important, including the size or the intensity of landslide events, made little difference to the death toll for landslides below about 20 feet depth. Similarly, the distance between a building and the landslide slope, or an inhabitant鈥檚 age and gender, didn鈥檛 make a big difference to their survival.
The results suggest practical ways to lower the number of lives lost to landslides in the United States, Wartman said. He hopes the information can be incorporated in education and community awareness programs.
鈥淭his is a message of hope,鈥� Wartman said. 鈥淲hat this work suggests is that a modest investment put toward social science, policy and education could have a very marked effect in protecting people from landslides.鈥�
Residents who want to know if they are vulnerable to landslides can contact a local agency, such as the Washington State Department of Natural Resources, to learn more about local risks. Federal is pending to make this information more easily accessible across the United States, Wartman said.
The study was funded by the National Science Foundation.
For more information, contact Wartman at wartman@uw.edu or Pollock at wpollock@uw.edu.
Adapted from an by Jack Lee for AGU Eos.