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Home damaged by rainfall-triggered debris flow - Carrol County, Kentucky
Landslides occur in all 50 states and territories, and they affect lives, property, infrastructure, and the environment. Landslides are the downslope movement of earth materials (rock, debris, and soil) at rates that range from inches per year to tens of miles per hour. Some landslides can move faster than a person can run and can happen with no notice or can take place over days, weeks, or longer
Sources/Usage: Public Domain.
Landslide that filled a home and buried a road in Utuado, Puerto Rico.
Landslides can bury homes, damage critical infrastructure, block or damage roads and rail lines, and disrupt vital utilities and communication lines. Landslides can happen with no notice or can take place over a period of days, weeks, or longer. Landslides are unpredictable. A slow-moving landslide can rapidly change to a fast-moving landslide. Some fast-moving landslides can travel thousands of feet, even across flat ground. A landslide can remain inactive for centuries and then suddenly start moving again. Although not as dangerous to human life as fast-moving landslides, a slow-moving landslide that may be moving a few inches per year can, over periods of months to years, severely damage and destroy building, roads, pipelines, and other utilities built on and adjacent to the landslide.
Landslides come in many varieties, from small rockfalls or debris flows (mudflows) that occur quickly to mountain-sized slides that move for centuries. Many landslides are complex and involve a variety of landslides themselves, such as large, slow-moving landslides that produce smaller but rapid debris flows.
Sources/Usage: Public Domain. Visit Media to see details.
An image of 24 June 2020 (B4) and prehistoric (P2) outlier rockfall boulders within the Mount Whitney Trailhead Campground.
Volcanic mudflows (lahars and debris flows) occur more commonly after a landscape has been covered by loose volcanic material. Sign on the slopes of Rabaul, Papua New Guinea.
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Debris flow caused by intense rainfall in April 2020 in Macon County, NC.
Bill Schulz, USGS Research Geologist, takes photographs of Puerto Rican hillsides from a U.S. Army helicopter to document landslides caused by Hurricane Maria. This work will help identify areas around Puerto Rico with the highest risk of more landslides, which is information the Federal Emergency Management Agency will use to determine the best way to mitigate and prepare for any future landslides. Photo by Jason Marineau, DOI Office of Emergency Management.
Landslides can be triggered by rainfall from hurricanes and rainstorms, ground shaking from earthquakes, and volcanic activity. Human activity commonly triggers landslides, such as modifying (grading) a slope, removing vegetation, or channeling water onto a slope. Local terrain conditions, such as slope steepness and curvature, and geologic materials make hillslopes more or less likely to experience landslides.
A landslide that moves into water can produce a displacement wave, which is a type of tsunami. The largest displacement wave in the world occurred in 1958 in Lituya Bay, Alaska when an earthquake triggered a landslide that rapidly moved into the bay. The resulting displacement wave was over 1,700 feet high and stripped trees and soils from the slopes along the Lituya Bay.
Sources/Usage: Public Domain. Visit Media to see details.
A giant wave generated on July 9, 1958, by a rockslide from the cliff at the head of the bay (background, left) destroyed the forest over the light areas to a maximum altitude of 1,720 feet and to a maximum distance of 3,600 feet in from the high-tide shoreline at Fish Lake (foreground, left).
Areas recently burned by wildfires can be more susceptible to landslides from rainfall. Fire can destroy vegetation and alter soil properties, such that water is repelled by a soil. During a rain event over a burned area, the soils may not be able to absorb water and instead, the water beads on the surface. If the soils are on a slope, the water will flow downslope and can rapidly increase in volume, picking up debris.
Sources/Usage: Public Domain.
Photograph of channel near Calwood Monitoring Station in the Calwood burn area
In the right conditions, the water can collect sufficient soil, rocks, and other debris and become a debris flow, which are very dangerous to those living downslope. Debris flows can damage or destroy roads, building, and other infrastructure far outside of the burned area.
Sources/Usage: Public Domain.
On Sunday, August 16, 2020 at approximately 3:00 PM PST, the River wildfire ignited in Monterey County, California. Debris-flow deposits at the Chualar and Limekiln sites within the River Burn area were observed on Wednesday, January 27, 2021, likely triggered by rainfall events in the early morning hours of January 27, 2021.
Wildfire can increase landslide susceptibility in mountainous terrain. The USGS maintains postfire landslide monitoring stations to track hillslope hydrologic conditions in the years following fire.
Postfire Landslide Monitoring Station: “Maria Ygnacio” (2019 Cave Fire) near Santa Barbara, California
Wildfire can increase landslide susceptibility in mountainous terrain. The USGS maintains postfire landslide monitoring stations to track hillslope hydrologic conditions in the years following fire.
House damaged by debris flows generated in Mullally Canyon in response to a rainstorm on February 6, 2010. The drainage basin above this home was burned the previous summer by the Station Fire, the largest fire in the history of Los Angeles County.
Landslides can have cascading consequences; for example, a landslide can form a debris dam that blocks a stream channel, forming a pond. The rising pond water can eventually breach the debris dam which can lead to downstream flooding. Or a landslide-damaged road can cause closures, forcing vehicles to take alternate routes for weeks to months. This can impact local economies and hinder emergency response. The frequency and size of landslides are expected to grow in areas due to climate change, which is increasing rainfall intensity that can trigger landslides. Climate change is also linked to more frequent and severe wildfires and recently burned areas can experience increased occurrence of landsliding due to the fire altering the soil and vegetation.
Sources/Usage: Public Domain.
Landslide at La Conchita, California
In the United States, financial loss from landslide damages is not well-documented; however, landslides are estimated to cause billions of dollars in damage and multiple deaths annually. In additional, indirect loss from landslides, such as cost to commercial traffic due to extended road closures by landslide damage, are also not well understood.
More importantly, if a home is damaged by a landslide, the typical homeowner’s insurance policy does not cover earth movement. So, the damage to a home from a landslide may be entirely covered by the homeowner.
People who live in areas with landslide hazards should learn the signs of a landslide and learn what to do after a landslide occurs.
Summer storms on the Grizzly Creek burn area have resulted in repeated flooding and debris flows that are having enormous impacts in Glenwood Canyon. This Story Map collection summarizes the June and July events.
Glenwood Canyon, Colorado, Flooding and Debris Flows: 2021
Summer storms on the Grizzly Creek burn area have resulted in repeated flooding and debris flows that are having enormous impacts in Glenwood Canyon. This Story Map collection summarizes the June and July events.
Southern California has a long history of damaging debris flows after wildfire. Despite recurrent loss, forecasts of the frequency and magnitude of postfire debris flows are not available for the region like they are for earthquakes. Instead, debris flow hazards are typically assessed in a reactive manner after wildfires. Such assessments are crucial for evaluating debris flow risk by postfire eme
Rocky, alpine mountains are prone to mass wasting from debris flows. The Chalk Cliffs
study area (central Colorado, USA) produces debris flows annually. These debris flows
are triggered when overland flow driven by intense summer convective storms mobilizes
large volumes of sediment within the channel network. Understanding the debris flow
hazard in this, and similar alpine settings, requires
Authors
Francis K. Rengers, Jason W. Kean, Nadine G. Reitman, Joel B. Smith, Jeffrey A. Coe, Luke McGuire
Summer storms on the Grizzly Creek burn area have resulted in repeated flooding and debris flows that are having enormous impacts in Glenwood Canyon. This Story Map collection summarizes the June and July events.
Glenwood Canyon, Colorado, Flooding and Debris Flows: 2021
Summer storms on the Grizzly Creek burn area have resulted in repeated flooding and debris flows that are having enormous impacts in Glenwood Canyon. This Story Map collection summarizes the June and July events.
Southern California has a long history of damaging debris flows after wildfire. Despite recurrent loss, forecasts of the frequency and magnitude of postfire debris flows are not available for the region like they are for earthquakes. Instead, debris flow hazards are typically assessed in a reactive manner after wildfires. Such assessments are crucial for evaluating debris flow risk by postfire eme
Rocky, alpine mountains are prone to mass wasting from debris flows. The Chalk Cliffs
study area (central Colorado, USA) produces debris flows annually. These debris flows
are triggered when overland flow driven by intense summer convective storms mobilizes
large volumes of sediment within the channel network. Understanding the debris flow
hazard in this, and similar alpine settings, requires
Authors
Francis K. Rengers, Jason W. Kean, Nadine G. Reitman, Joel B. Smith, Jeffrey A. Coe, Luke McGuire
