NASA Study Discovers Climate Extremes Affect Landslides in Surprising Manners

The outcomes represent an initial step toward developing what scholars expect will become the capacity to foresee whether a slow-moving landslide will fail and slide downhill.

Climate modification is leading more volatile precipitation patterns worldwide– very dry stretches punctuated by storms that drop large quantities of rain or snow in a short period of time. While wetter and also drier spells might have specific effects that are easy to foresse, such as on water levels in lakes and rivers, a current study focused on California shows that they could affect slow-moving landslides in unforeseen manners.

The researchers expected slow-moving landslides– where land creeps downhill simply inches to feet in a year– in bone-dry Southern California to act differently from those in rainy Northern California when exposed to heavy precipitation and drought conditions. Yet that was not the case. The research authors found that landslides in wetter and drier areas of California showed similar sensitivity to precipitation extremes, moving on average higher and farther downhill during rainy periods compared to drought years.

Water triggers landslides, and understanding how landslides react to record drought, or severe rainfall can help scientists better anticipate their future behavior, including whether any can collapse or fail catastrophically. The big-picture objective is to develop a statewide inventory of landslide actions to inform a monitoring network. While slow-moving landslides do not necessarily pose an immediate danger to people or infrastructure, they can damage things like roads and buildings over time. And in some instances, they could suddenly collapse, which is what happened with the Mud Creek landslide near Huge Sur in 2017.

“I thought the outcomes would be quite different between Northern and also Southern California,” stated Alexander Handwerger, one landslide scientist at NASA’s Jet Propulsion Laboratory in Southern California and the lead writer of the study, which was recently released in Geophysical Research Letters. His work up until this paper focused on landslides in Northern California, so he was not sure what he ‘d see when he looked at drier parts of the state.

Surprising behavior

California hosts more than 650 slow-moving landslides, and Handwerger and his colleagues focused on 247 slow-moving landslides with an average area of 0.2 square miles (0.5 square kilometres). They then analyzed a subset of thirty-eight that differed in how much rainfall they got, the rock kinds they were made of, the environments in which they happened (coastal versus inland), and whether they were in developed or undeveloped locations.

The researchers looked at how those landslides acted from 2015 to 2020, one period with broad swings in precipitation: Whereas 2017 was the 2nd-wettest year on document for certain parts of California, 2015 and 2016 were exceptionally dry years.

They acquired data on landslide motion utilizing information collected by the ESA (European Space Agency) Sentinel-1 satellites. The measurements were automatically processed into maps showing land motion by the JPL-Caltech Advanced Rapid Imaging and Analysis (ARIA) Center for Natural Hazards project. (Caltech, in Pasadena, manages JPL for NASA.).

The scientists knew that slow-moving landslides in wetter parts of the state stayed fairly saturated throughout the year. They didn’t expect to find that both currently waterlogged landslides and their drier counterparts acerated and moved farther downhill during wet times compared to drier times.

Projecting the future

Getting one better handle on why landslides react the way they do to rainfall or drought could help scientists predict future events like the Mud Creek landslide. It collapsed during one very wet year for California in which similar landslides did not collapse. “We’re trying to understand why this occurs,” Handwerger stated.

A better understanding of landslide behavior might allow a monitoring network that provides alerts to local and state officials, in addition to researchers, to watch on a landslide or team of landslides that began acting differently. It could also assist with building a warning system for communities in risk from a landslide, along with influence planning related to development and infrastructure.

Secret to such a monitoring network is the capability to perform large-scale, detailed research. And those are made possible by advances in satellite innovation, allowing spacecraft such as Sentinel-1 to give more regular, exact data on changes in Earth’s surface over more extensive areas. Future missions like NISAR (short for the NASA-Indian Space Research Organisation Synthetic Aperture Radar satellite) will monitor changes to Earth’s surface utilizing a different radar frequency that can better “see” through vegetation compared to Sentinel-1. Like that mission, NISAR will make its information freely available to the public.

Time-intensive, data-heavy analyses are also obtaining easier to perform because of projects like ARIA and one upcoming NASA-sponsored project called OPERA (or Observational Items for End-Users from Remote Sensing Analysis). OPERA, managed by JPL, will utilize measurements from missions like Sentinel-1 and NISAR to generate data products showing modifications to Earth’s surface. These products will provide resource managers, federal agencies, and researchers– among others– detailed measurements of much of North and Central America, eliminating the need to spend time working the data into a format suitable for analysis and decision-making.

Read the original article on NASA.

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