Research by UC Berkeley scientists has uncovered more precise ways of predicting the sizes of shallow landslides.
Led by campus geography assistant project scientist Dino Bellugi and earth and planetary science professor William Dietrich, the researchers found that a hillside’s topographical characteristics can be used to determine landslide size ranges. There is more work to be done, however, in order to more precisely predict landslide sizes and prepare for the potential risks.
“We have a large number of people living in communities that are in hilly areas or near hilly areas at the base of mountains,” Dietrich said. “That’s a recurring risk.”
The study employed the aerial mapping tool LiDAR, or light detection and ranging, which uses lasers to reconstruct landscape surfaces, according to Bellugi. By shooting laser pulses into hillsides and determining distances between objects based on how the pulses bounce back, researchers can predict which areas are more susceptible to landslides.
Previous models of landslide prediction have sometimes resulted in unnecessary evacuations among residents, according to Bellugi. This study aimed to determine how to more accurately predict individual landslide occurrences based on factors such as shapes, materials and wetness levels of slopes, according to David Milledge, study contributor and Newcastle University research fellow.
“(Our research) takes us a little further into the three questions of where, when and how big (landslides will be),” Bellugi said. “It also helps us make more accurate predictions about how much material we can expect coming down from a hill slope in the form of landslides and the range of sizes we can expect.”
For this study, researchers tested their landslide prediction model on two field sites – one in Oregon and one in England. Despite these locations being topographically different, their landslide size distributions were “identical,” Bellugi said, leading him and his team to consider the impact of hill slope strength on landslide occurrence.
If a hillside’s physical characteristics, such as its root and soil strength, are uniformly distributed, small landslides have the capacity to turn into big ones, according to Bellugi. Researchers, therefore, predict that the variability of hill slope strength determines whether or not a shallow landslide will be small or large.
“The landslides can occur in weak locations in the landscape, but if these locations aren’t separated enough by high-strength areas, they can collapse and form bigger landslides,” Bellugi said.
One of the study’s most significant findings is that future research into landslide predictions must take into account the spatial variability of hillside properties, according to Bellugi. By mapping out the physical characteristics of landscapes, scientists need to do more ground research before they can eventually predict the range of landslide sizes that could occur.
For Milledge, this study marks the completion of nearly 20 years worth of work into landslide prediction.
“For particularly Dino and I, it’s been a piece of work that we’ve kind of chipped away at,” Milledge said. “It’s been like Zoom call after Zoom call, late nights and chipping away, and it’s just really great to finally have it out there.”