Overview
According to the U.S. Geological Survey (USGS) landslides are a “movement of a mass of rock, debris or earth down a slope. Landslides are a type of ‘mass wasting,’ which denotes any down-slope movement of soil and rock under the direct influence of gravity. The term ‘landslide’ encompasses five modes of slope movement: falls, topples, slides, spreads and flows. These are further subdivided by the type of geologic material (bedrock, debris or earth). Debris flows (commonly referred to as mudflows or mudslides) and rock falls are examples of common landslide types.”
Gravity is the primary factor in landslides, but erosion, saturated ground, earthquakes, volcanic eruptions, excess weight from rain or snow contribute to ground movements (rock falls, deep failure of slopes and shallow debris flows).
The majority of landslides do not affect humans, but the ones that do are devastating to homes, businesses and infrastructure. A 2014 slide in Oso, Washington essentially buried an entire neighborhood when an unstable hill collapsed and sent a cascade of mud and debris across an area coving about one square mile.
Most major landslides are so-called “secondary hazards” triggered by another disaster, like an earthquake, volcanic eruption or erosion after a wildfire; the majority of tsunamis are triggered by underwater landslides. Experts believe that a September 2018 tsunami in Palu, Indonesia was likely caused by such a landslide following an earthquake.
Key Facts
- Landslides are the one natural disaster that can strike anywhere at almost any time.
- On average, landslides cause between $1 – 2 billion in damage in the United States each year.
- In the U.S., 25 to 50 people are killed in landslides annually, but worldwide that number is in the thousands.
- Two of the largest recent landslides occurred in Washington state. The 1980 eruption of the Mount St. Helens volcano in the Cascade Mountain Range saw a landslide with a volume of material of 67 cubic miles. The March 22, 2014 landslide in Oso resulted in 43 deaths, with damage to approximately 50 homes and one square mile of land, rivers and infrastructure were destroyed.
How to Help
- Planning reduces catastrophic loss. By investing in hazard analysis and mapping to guide land-use decisions, the potential for catastrophic loss can be reduced. By using GIS in combination with satellite images, it is possible to create detailed maps that show highly probable areas for future landslides. Land use planning, including zoning certain areas as unsafe for development will not always reduce the chance of a landslide but can minimize damage.
- Physical barriers can prevent damage. In cases where potential landslides could affect existing structures, physical controls can be used. This can include building buttresses and walls or inserting anchors into the base of hills and slopes that show a high probability for landslide events.
- Warning systems can save lives. In certain areas, monitoring and warning systems are warranted to guard against the loss of life. Landslide advisories make communities aware that rainfall may lead to debris-flow activity and they should take precautions if there is heavy rain. Landslide watches indicate that landslide activity is possible and preparedness activities should be undertaken, whereas a landslide warning means activity is occurring. Tsunami warning systems can also let people know to move to higher ground or otherwise out of harm’s way when a tsunami is predicted.
- Support search and rescue or family reunification. Following a major landslide there is a need for specialized search and rescue teams who are trained in working in hazardous conditions. When a significant number of people are trapped or missing, funders can support family reunification centers and teams, as well as emotional/spiritual care for disaster responders.
What Funders Are Doing
- The New York Life Foundation, which focuses on children’s bereavement issues, provided a $10,000 grant to Camp Fire following the Oso mudslides to enable children who had lost a family member to attend Camp Killoqua’sCamp Willie: a grief camp for young people in grades 2-12. Camp Willie is a decade-old program offered by Camp Fire to support young people through a combination of camp activities and programs to help with the experience of grieving.
- The B. Cheney Foundation, which supports quality of life grants in areas where Mr. Cheney’s lumber company was active, made a $10,000 grant to the Snohomish County Volunteer Search and Rescue Unit to support their efforts to locate victims of the Oso mudslide.
- The Fondo Accion Solidaria made a $2,695 grant in 2016 to Sociedad Cooperativa Lequil Kuxlejal ta Cancuc to support the reduction of landslides in the members’ coffee plantations and plots. The goal was to plant fruit trees to stabilize the soil and diversify the shade species. The improved biodiversity served not only to diversify food sources but also prevent soil erosion.