Landslide information

Although the information doesn't exactly paint a picture of what happened with the landslide in Colombia, the following information can help us determine what might have caused such a disaster.

Landslide Hazard Information

Landslides cause fatalities and billions of dollars in property damage each year.

Republished from United States Geological Survey Fact Sheet 2004-3072.

Landslides in the United States occur in all 50 States. The primary regions of landslide occurrence and potential are the coastal and mountainous areas of California, Oregon, and Washington, the States comprising the intermountain west, and the mountainous and hilly regions of the Eastern United States. Alaska and Hawaii also experience all types of landslides.

Landslide Incidence and Susceptibility Map

USGS map of relative landslide incidence and susceptiblity across the conterminous United States. Red and pink areas have the highest incidence and susceptibility. USGS Map . Enlarge Image

Landslides in the United States cause approximately $3.5 billion (year 2001 dollars) in damage, and kill between 25 and 50 people annually. Casualties in the United States are primarily caused by rockfalls, rock slides, and debris flows. Worldwide, landslides occur and cause thousands of casualties and billions in monetary losses annually.

Landslide Hazard Information Homeowners Insurance Does Not Cover Landslides Landslides in the News

The information presented here provides an introductory primer on understanding basic scientific facts about landslides-the different types of landslides, how they are initiated, and some basic information about how they can begin to be managed as a hazard.

Types of Landslides

The term "landslide" describes a wide variety of processes that result in the downward and outward movement of slope-forming materials including rock, soil, artificial fill, or a combination of these. The materials may move by falling, toppling, sliding, spreading, or flowing. The drawing below is a graphic illustration of a landslide, with the commonly accepted terminology describing its features.

Anatomy of a Landslide

Figure 1. An idealized slump-earth flow showing commonly used nomenclature for labeling the parts of a landslide. Enlarge Image

Although landslides are primarily associated with mountainous regions, they can also occur in areas of generally low relief. In low-relief areas, landslides occur as cut-andfill failures (roadway and building excavations), river bluff failures, lateral spreading landslides, collapse of mine-waste piles (especially coal), and a wide variety of slope failures associated with quarries and open-pit mines. The most common types of landslides are described and illustrated at right.

Slides Although many types of mass movements are included in the general term "landslide," the more restrictive use of the term refers only to mass movements, where there is a distinct zone of weakness that separates the slide material from more stable underlying material. The two major types of slides are rotational slides and translational slides. Slide types, images and descriptions at right. Flows There are five basic categories of flows that differ from one another in fundamental ways. Flow types, images and descriptions at right. Although there are multiple types of causes of landslides, the three that cause most of the damaging landslides around the world are these: Landslides and Water Slope saturation by water is a primary cause of landslides. This effect can occur in the form of intense rainfall, snowmelt, changes in ground-water levels, and waterlevel changes along coastlines, earth dams, and the banks of lakes, reservoirs, canals, and rivers. Landsliding and flooding are closely allied because both are related to precipitation, runoff, and the saturation of ground by water. In addition, debris flows and mudflows usually occur in small, steep stream channels and often are mistaken for floods; in fact, these two events often occur simultaneously in the same area. Landslides can cause flooding by forming landslide dams that block valleys and stream channels, allowing large amounts of water to back up. This causes backwater flooding and, if the dam fails, subsequent downstream flooding. Also, solid landslide debris can "bulk" or add volume and density to otherwise normal streamflow or cause channel blockages and diversions creating flood conditions or localized erosion. Landslides can also cause overtopping of reservoirs and/or reduced capacity of reservoirs to store water. Landslides and Seismic Activity Many mountainous areas that are vulnerable to landslides have also experienced at least moderate rates of earthquake occurrence in recorded times. The occurrence of earthquakes in steep landslide-prone areas greatly increases the likelihood that landslides will occur, due to ground shaking alone or shaking- caused dilation of soil materials, which allows rapid infiltration of water. The 1964 Great Alaska Earthquake caused widespread landsliding and other ground failure, which caused most of the monetary loss due to the earthquake. Other areas of the United States, such as California and the Puget Sound region in Washington, have experienced slides, lateral spreading, and other types of ground failure due to moderate to large earthquakes. Widespread rockfalls also are caused by loosening of rocks as a result of ground shaking. Worldwide, landslides caused by earthquakes kill people and damage structures at higher rates than in the United States. Landslides and Volcanic Activity Landslides due to volcanic activity are some of the most devastating types. Volcanic lava may melt snow at a rapid rate, causing a deluge of rock, soil, ash, and water that accelerates rapidly on the steep slopes of volcanoes, devastating anything in its path. These volcanic debris flows (also known as lahars) reach great distances, once they leave the flanks of the volcano, and can damage structures in flat areas surrounding the volcanoes. The 1980 eruption of Mount St. Helens, in Washington triggered a massive landslide on the north flank of the volcano, the largest landslide in recorded times. Landslide Mitigation - How to Reduce the Effects of Landslides Vulnerability to landslide hazards is a function of location, type of human activity, use, and frequency of landslide events. The effects of landslides on people and structures can be lessened by total avoidance of landslide hazard areas or by restricting, prohibiting, or imposing conditions on hazard-zone activity. Local governments can reduce landslide effects through land-use policies and regulations. Individuals can reduce their exposure to hazards by educating themselves on the past hazard history of a site and by making inquiries to planning and engineering departments of local governments. They can also obtain the professional services of an engineering geologist, a geotechnical engineer, or a civil engineer, who can properly evaluate the hazard potential of a site, built or unbuilt. The hazard from landslides can be reduced by avoiding construction on steep slopes and existing landslides, or by stabilizing the slopes. Stability increases when ground water is prevented from rising in the landslide mass by (1) covering the landslide with an impermeable membrane, (2) directing surface water away from the landslide, (3) draining ground water away from the landslide, and (4) minimizing surface irrigation. Slope stability is also increased when a retaining structure and/ or the weight of a soil/rock berm are placed at the toe of the landslide or when mass is removed from the top of the slope.

Interesting study on Alaskan wildfires

Accelerated Wildfires Unlocking Carbon in Alaskan Soils, Study Finds

December 06, 2010 - News Release

Photo Credit:NRCan-CFS
Climate change is causing wildfires to burn more fiercely, pumping more greenhouse gases into the atmosphere than previously thought, according to a new study to be published in Nature Geosciences this week.
This is the first study to reveal that fires in the Alaskan interior - an area spanning 18.5 million hectares - have become more severe in the past 10 years, and have released much more carbon into the atmosphere than was stored by the region’s forests over the same period.
“When most people think of wildfires, they think about trees burning, but most of what fuels a boreal fire is plant litter, moss and organic matter in surface soils,” said University of Guelph professor Merritt Turetsky, lead author of the study.
“These findings are worrisome because about half the world’s soil carbon is locked in northern permafrost and peatland soils. This is carbon that has accumulated in ecosystems a little bit at a time for thousands of years, but is being released very rapidly through increased burning.”
The results of this study are important for countries currently meeting in Mexico for climate talks, added the integrative biology professor.
“Essentially this could represent a runaway climate change scenario in which warming is leading to larger and more intense fires, releasing more greenhouse gases and resulting in more warming. This cycle can be broken for a number of reasons, but likely not without dramatic changes to the boreal forest as we currently know it.”
This study is part of a growing body of evidence that northern systems are bearing the brunt of climate change, said co-author Jennifer Harden, a U.S. Geological Survey scientist.
“This includes longer snow-free seasons, changes in vegetation, loss of ice and permafrost, and now fire, which is shifting these systems from a global carbon sink toward a carbon source.”
The researchers visited almost 200 forest and peatland sites shortly after blazes were extinguished to measure how much biomass burnt.
“We’ve been chasing fires in this region for a number of years, which is how we amassed this unique data set,” said Turetsky.
They also looked at fire records kept since the 1950s.
“Over the past 10 years, burned area has doubled in interior Alaska, mostly because of increased burning late in the fire season,” said co-author Eric Kasischke, a University of Maryland professor. “This is the first study that has demonstrated that increases in burned area are clearly linked to increases in fire severity. This not only impacts carbon storage, but also will accelerate permafrost loss and changes in forest cover.”
More severe burning also raises a number of health concerns, as fire emissions contain mercury and particulate matter that can cause respiratory issues, said Turetsky.
“We are hoping people will recognize the seriousness of climate change for northern regions and people living in them. Wildfire is going to play a more and more important role in shaping the north.”

Landslide kills nearly 50 in Colombia

Rescue workers in the town of Bello where a landslide on Sunday destroyed 35 houses have recovered 47 bodies from the rubble, authorities announced on Wednesday. 80 people are still missing.
Following a short suspension of the work because of heavy rains, policemen, soldiers and Red Cross volunteers returned to look for victims early Wednesday morning, which resulted in the finding of eight more victims.
So far, at least 22 children were recovered from under the rubble.
Mourning family members and friends of victims of the landslide in the town just north of Medellin started burying their loved ones on Tuesday following a mass service in the local church.


 Related story below:


Colombia's President Juan Manuel Santos declared a state of emergency to cope with the catastrophe caused by this year's rainy season, which has killed more than 200, uprooted thousands of families, and affected more than 1.6 million Colombians.
"Tonight we are taking the decision to firstly declare a disaster situation [in the town of Bello] and secondly declare an economic, social and ecological emergency ... initially for 30 days, but it can be extended to 90 days," the president said in a televised speech after returning from the town just north of Medellin where a landslide is feared to have killed 124 residents of a poor hillside slum.
The state of emergency will allow the government to take a number of measures in the short, medium and long term and will consist of three phases, said Santos.
"The first will be dedicated to humanitarian aid, as in saving lives and providing shelter and food to the approximately 330,000 families that need this. The second will be a phase of rehabilitation to repair the roads, schools, power networks and other infrastructural works that must be recovered. The third phase - which will be the biggest and most ambitious of all - will be reconstruction, which implies the repair of everything that has been destroyed or has become useless," the president said.
Santos explained that he and his ministers decided to declare the emergency because the gravity of the situation in Colombia has exhausted the government's capacity. According to the president, Bogota has already invested COP0.5 trillion ($264 million) in attending to the problems caused by the extended rainy season. "The needs go beyond our economic capacity and have also flooded the agencies specialized in disaster attention," said Santos.
This year's extended rainy season - caused by weather phenomenon "La Niña" - started in March and has devastated the country. According to the government, 80% of the country's roads are damaged, more than 200 persons are confirmed killed by floods and landslides, 1.6 million people have suffered damage to their homes or lands, and many hectares of crops were lost in floods.
To help mitigate the effects of the disastrous rainy season, the U.S. ambassador to Bogota on Tuesday announced his country will donate a total of $1 million to the Colombian branch of the Red Cross to provide immediate help to victims. The Inter-American Development Bank (IDB) offered Colombia a $350 million loan, and United Nations Secretary General Ban-Ki Moon promised to "do everything possible to help."

Colombia's Consul General in Miami opened a number of U.S. bank accounts and a PayPal account where foreigners and migrants can donate money. Colombia's embassy in Washington is working on its website to allow donations to be given directly through the website. Several social organizations in the U.S. and Colombia are also looking for donations.



The above stories came from Columbiareports.com after a landslide destroyed homes and killed nearly 50 people. Probably the more interesting of the two is the bottom story, which discusses the government's response to the disaster. As we learned in class, declaring a state of emergency means money for the areas damaged - although in this case it sounds like it is coming from places other than the government. Although the article discusses the heavy rainy, it would have been interesting to read a little bit more about the specifics of what caused the landslide.