New National Landslide Map

Benjamin B. Mirus, Gina M. Belair, Nathan J. Wood, Jeanne Jones, Sabrina N. Martinez, Parsimonious High-Resolution Landslide Susceptibility Modeling at Continental Scales, First published: 11 September 2024. Parsimonious High‐Resolution Landslide Susceptibility Modeling at Continental Scales - Mirus - 2024 - AGU Advances - Wiley Online Library 

The below is executed from the above cited article and the USGS press release.

Landslides when rock, debris, and soil move downhill at rates that ranging from inches per year to tens of miles per hour are a significant threat. Some move faster than a person can run, some can happen with no notice or can take place over a period of days, weeks, or longer.  Landslides occur in any area composed of very weak or fractured materials resting on a steep slope. This can happen in every state of the union. Reducing loss of life and minimizing community disruptions from future landslides requires an understanding of landslide potential and related direct and indirect effects. 

Now the U.S. Geological Survey has released a new nationwide landslide susceptibility map that finds nearly 44% of the U.S. could potentially experience landslides. The new assessment provides a highly detailed, county-by-county picture of where these damaging, disruptive and potentially deadly geologic hazards are more likely as well as areas where landslide hazards are negligible.

The new map will support risk-reduction and land-use planning efforts by showing where potentially unstable areas are so planners and engineers can better prioritize and mitigate future landslide hazards.“This new national landslide susceptibility map addresses an important but difficult question: which areas across the entire U.S. are prone to landslides?” said Ben Mirus, USGS research geologist. “We are excited that it is now publicly available to help everyone be more prepared – to be a more hazard-ready nation.”

As you can see below the fractured rock slopes of Virginia are susceptible to landslides.

In the past two decades, there have been several efforts to combine landslide-occurrence data with geospatial technology to develop more accurate and precise landslide-susceptibility maps. The USGS and collaborators proposed a prototype landslide-susceptibility map to inform potential landslide insurance policies (Godt et al., 2012). Their map was based on the empirical analysis of approximately 16,000 landslides from five inventories across as many different states to calibrate a landslide threshold for topographic slope and relief.

This  detailed landslide map was only developed for a few areas of the U.S. where the landslide risks were considered high, but now using all data available and better computer modeling tools this map expands the assessment to include many other hazardous areas around the country where there was a limited understanding of landslide potential.

Ben Mirus and the current research team used an inventory of nearly 1 million previous landslides, high-resolution national elevation data from the USGS 3D Elevation Program, and advanced computing to build their comprehensive landslide susceptibility model. The resulting map of the contiguous U.S., Alaska, Hawaii, and Puerto Rico zeroes in on landslide locations by using much higher resolution data than existing continental and global landslide maps.

The primary goal of the research team was to develop a high-resolution model based on empirical evidence that consistently delineates areas with any potential for landsliding across the entire country, while at the same time not over-representing hazardous areas. The secondary goal was to explore ways to express relative differences in landslide susceptibility, instead of simply noting “some” or “negligible” as has been done in previous studies (e.g., Godt et al., 2012). The topographic data used, as well as the expanded inventory of landslide data, represent an order-of-magnitude improvement over existing susceptibility maps with coverage over most of the United States. However, the variety of landslide type and geologic conditions under which slopes may fail simply cannot be accounted for by topography alone. This is an area where more work needs to be done.

The new landslide map shows higher susceptibility areas across the most mountainous regions of the United States, including the Appalachian Mountains, Rocky Mountains, Pacific Coast Ranges, and Cascade Range. The map also highlights the extensive mountainous terrain throughout Alaska, as well as the higher susceptibility characterized across Puerto Rico (Hughes & Schulz, 2020) and the Hawaiian Islands (Baum, 2018).