What is a landslide hazard map?
Several kinds of maps are used to depict danger from landslides. These maps may be as simple as a map that uses the locations of old landslides to indicate potential instability, or as complex as a quantitative map incorporating probabilities based on variables such as rainfall, slope angle, soil type, and levels of earthquake shaking. The following types of maps are used to describe and depict landslide hazards:
Landslide inventory maps show landslide locations and may show the dimensions and geographical extent of each landslide. Because one clue to the location of future landsliding is the distribution of past movement, maps that show the location and size of landslides are helpful in predicting the hazard for an area.
Examples of landslide inventory maps:
- Inventory of Landslides Triggered by the 1994 Northridge, California, Earthquake
- California Geological Survey Landslide Inventory Maps
Landslide susceptibility maps describe the relative likelihood of future landsliding based solely on the intrinsic properties of a locale or site. Some organizations use the term “landslide potential map” for maps of this kind. Prior failure (from a landslide inventory), rock or soil strength, and steepness of slope are three of the more important site factors that determine susceptibility.
Examples of landslide susceptibility maps:
- Susceptibility to Deep-Seated Landslides in California
- Landslide Susceptibility Estimated From Mapping Using Light Detection and Ranging (LIDAR) Imagery and Historical Landslide Records, Seattle, Washington
Landslide hazard maps indicate the possibility of landslides occurring throughout a given area. An ideal landslide hazard map shows not only the chances that a landslide may form at a particular place, but also the chance that it may travel downslope a given distance.
Examples of landslide hazard maps:
Examples of potential landslide maps:
- NASA Global Potential Landslide Areas
- Assessing landslide potential using GIS, soil wetness modeling and topographic attributes, Payette River, Idaho - 2001
Landslide risk maps show landslide potential along with the expected losses to life and property, should a landslide occur. Risk maps combine the probability information from a landslide hazard map with an analysis of all possible consequences (property damage, casualties, and loss of service).
The Mud Creek landslide on California’s Big Sur coast keeps eroding.
USGS is collecting and analyzing air photos to help monitor a huge landslide that occurred May 20 on California’s Big Sur coast.
New mapping in the western portion of the Columbia Gorge in Skamania County, Washington, shows previously unrecognized landslides beneath dense forest cover.
Two snapshots from Landsat show the extent of a landslide in an Alaska National Park.
New report identifies best practices for protecting communities
Scenic rock cliffs falling to valley floors, rocks ripping out mountainsides, mud and debris moving down valleys at deadly speeds, mines and caves collapsing, and ocean and river bluffs sliding into the water -- all describe one of the nation’s most underestimated hazards -- landslides.
Excerpt from the USGS Scientific Investigations Map 3358, “Landslides in the Western Columbia Gorge, Skamania County, Washington."
Photograph from an aerial survey showing the extent and impacts from the landslide in northwest Washington that occurred on March 22, 2014. The survey was conducted by the Washington State Department of Transportation, Washington State Department of Natural Resources, USGS, and King County Sheriff's Office.
Landslides occur in all 50 states and U.S. territories, and cause $1-2 billion in damages and more than 25 fatalities on average each year. USGS scientists aim to improve our understanding of landslide hazards to help protect communities and reduce associated losses.
- Types of Landslides
- USGS Science
- Did You See It?
- Debris Flow Early Warning System (NOAA Partnership)
- Tips for Homeowners
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon. Spectacular debris flow footage, recorded by Franck Lavigne of the Universite Paris, makes clear the destructive power of these flows.
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On January 10, 2005, a landslide struck the community of La Conchita in Ventura County, California, destroying or seriously damaging 36 houses and killing 10 people. For a USGS rerpot on this event, please see USGS Open-file report, "Landslide Hazards at La Conchita, California."