Using data to predict the next landslide

The Idaho Geological Survey has released a new, statewide inventory of landslide data with an aim of developing a tool that can predict the likelihood of future slides and potentially aid in transportation and civil planning, among other disciplines.

Claudio Berti, a state geologist and director of the Idaho Geological Survey, said the new database contains more than 2,400 landslide events, including everything from slides that are still considered active, to those that deformed the landscape thousands of years ago but are no longer active. He said the dataset is composed of information gleaned from archival data, field observations as well as relatively new data gathered through satellite imagery and LIDAR, which measures distances with lasers.

“It’s a substantial piece of work to establish a sort of a baseline, and it also allows us to finally have an analytic, quantitative estimate of areas that are affected by landslides and rock falls and, generally speaking, mass movement on hillslopes,” Berti said. “Our goal is to identify those areas, and slowly, as resources allow … to integrate the data and start laying down the foundation for something that can become predictive.”

Berti said LIDAR sensors in particular are phenomenal at cutting through impeding vegetation to create an accurate image of the landform beneath “and landform(s) are really the fingerprint for landslides.” He said a recent federal project provided LIDAR data for much of the southern part of the state but ideally, the agency would be able to conduct LIDAR surveys of the entire state over multiple years to determine how the landscape has shifted. He said GPS surveys have been useful in similar ways and he hopes to create a monitoring campaign where people help to report landslide activity to help create a clearer picture of that activity for Idaho’s geologists.

When envisioning landslides, Berti said people often picture acute events but landslides can also be slow-moving landmasses that shift slowly over the course of months or years.

“Landslides have a serious range of movement — some of them creep through many decades, and kind of keep encroaching on the same area and maybe all they do is, let’s say, deform, slowly, a road that crosses the toe of the landslide,” he said. “There are other landslides that instead may not be visible or may not present any sign of activity or signs that there may be a landslide at all, and all of a sudden, a big chunk of a mountain falls down.”

Berti said Idaho is among states that experience a high level of landslide activity. He said an easy example is the slide just south of Riggins that took place in July of last year on U.S. Highway 95. It limited traffic for months and was only fully cleared in November.

Another, less severe slide took place near that same location — about seven miles north of Riggins — on Thursday. Within hours, the Idaho Transportation Department cleared enough of the debris to allow a single lane of traffic through the area. As of Friday afternoon, ITD officials said they aimed to have two lanes of traffic operational by sundown.

While it will likely take years to develop a tool capable of predicting where landslide risk is highest, Berti said as a state agency, ideally the Idaho Geological Survey would provide actionable data to stakeholders of all kinds. He said this includes civil engineers, developers and potential homeowners, so they are better informed about where the risk is greatest.

“For people who live in a state that is highly mountainous like Idaho, it’s similar to the information that people need when they live near the coast or near a floodplain,” Berti said. “You will need to know whether there is a risk and what is the probability for the house to be flooded so they can act and buy insurance or decide otherwise.”

Jackson can be reached at (208) 883-4636, or by email to sjackson@dnews.com.