Landslide

In the early hours of August 2, 2014, nearly 2 kilometers of hillside collapsed in rugged northern Nepal. Image: NASA.

Definition

The term “landslide” refers to a 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 (UNDRR).

A landslide is a downslope movement of rock or soil, or both, occurring on the surface of rupture, either curved (rotational slide) or planar (translational slide) rupture, in which much of the material often moves as a coherent or semi coherent mass with little internal deformation (USGS).

Facts and figures

According to the International Disaster Database of the Centre for Research on the Epidemiology of Disasters, in the period from 2000 to 2014, 26,000 persons have lost their lives because of landslides and flash floods while the economic losses amounted to over US$ 40 billion (OFDA/CRED).

Landslides can be classified into different types on the basis of the type of movement and the type of material involved. In brief, material in a landslide mass is either rock or soil (or both); the latter is described as earth if mainly composed of sand-sized or finer particles and debris if composed of coarse fragments. The type of movement describes the actual internal mechanics of how the landslide mass is displaced: fall, topple, slide, spread, or flow. Thus, landslides are described using two terms that refer respectively to material and movement, that is rockfall, debris flow, and so forth. Landslides may also form a complex failure encompassing more than one type of movement that is, rock slide and debris flow (USGS).

The primary driving factor of landslides is gravity acting on a portion of a slope that is out of equilibrium. The following are some of the major landslide triggering mechanisms:

  • River erosions, glaciers, or ocean waves
  • Weakening of rock and soil slope properties through water saturation by snowmelt or heavy rains
  • Stresses, strains and excess of pore pressures induced by the inertial forces during an earthquake (earthquakes of magnitude greater than or equal to 4.0 can trigger landslides)
  • Volcanic eruptions with the production of loose ash deposits that may become debris flows (known as lahars) during heavy rains
  • Stockpiling of rock or ore, from waste piles, or from man-made structures
  • Changes of the natural topography caused by human activity (UNDRR).

Related content

Événement

WLF logo. Image: WFL
The International Consortium on Landslides and the Global Promotion Committee of International Programme on Landslides will organize the Fifth World Landslide Forum (WLF5) on 2-6 November 2021 in Kyoto, Japan. The aim of this Forum is to promote and share knowledge and best practices about landslide risk mitigation, monitoring and early warning.
 
The forum will discuss the following topics:
  • Sendai Landslide Partnerships and Kyoto Landslide Commitment
  • ... read more
RUS Webinar – Rapid Landslide Detection with Sentinel-1. Image: RUS

During this webinar, participants will employ RUS to learn how to detect rapid landslides, by analysing the Fagraskógarfjall landslide that occurred in western Iceland in July 2018. 

Participants will use Sentinel-1 products to detect and map the extent of the landslide. They will be shown how to access the RUS Service and how to download, process, analyse and visualize the free data acquired by the Copernicus satellites.

Image: NASA.

Learning Objectives: 


By the end of this training, attendees will be able to:

  • Create a flood map using Google Earth Engine
  • Generate a map characterizing areas where landslides have occurred
  • Generate a digital... read more
CSSTEAP logo. Image: CSSTEAP.

The Asia-Pacific region faces major disaster risks in the form of earthquakes and tsunamis, tropical cyclones and typhoons, landslides, flash floods, avalanches and glacial lake outburst floods (GLOFs). Due to the large ... read more

Advisory Support

At the request of the Government of Sri Lanka, through the Ministry of Disaster Management (MoDM), UN-SPIDER carried out a Institutonial Strenghtening Mission follow-up activity to Sri Lanka to understand long-term capacity building needs and discuss joint activities in next three to five years.

Mission dates: 22/03/2018 to 28/03/2018

At the request of, and in coordination with the National Civil Protection Office of Tunisia, UN-SPIDER is conducting a Technical Advisory Mission to Tunisia from 4 to 6 March 2020 to identify the needs of the country to fully take advantage of space-based information for disaster management. In order to discuss the use of space-based information for risk and disaster management to subsequently make recommendations on improvements, the expert team meets with key disaster management authorities in the country.

The mission is conducted with the support of experts from the Algerian Space Agency (ASAL); the Romanian Space Agency (ROSA); the United Nations Economic Commission for Africa (UNECA); the National Observatory of Athens (NOA); and an expert on the Copernicus Emergency Management Service. The mission team is also benefiting from the support of the Chief of Space Applications of the United Nations Office for Outer Space Affairs.

As part of the mission, the team of experts will visit several institutions including the National Office of Civil Protection; the Directorate General for Forests of the Ministry of Agriculture; the Faculty of Sciences of Tunis, University of Tunis El Manar; the National Agronomic Institute of Tunisia; the National Institute of Meteorology; as well as at the Ministry of Local Affairs and Environment. Meetings will also be conducted with representatives of the National Cartographic and Remote Sensing Centre of Tunisia and other organizations. In addition, the TAM team will meet the United Nations Country Team in Tunisia, which supports disaster management efforts in the country.

During the TAM, a workshop with over 20 participants from nine institutions will take place in order to present the UN-SPIDER programme to Tunisian counterparts involved in disaster management, and encourage inter-institutional cooperation and sharing of geospatial information among them.

UN-SPIDER aims at ensuring all countries have the capacity to use all types of space-based information to support risk and disaster management efforts. To make sure that all interested stakeholders can benefit from this information in the most effective way possible, UN-SPIDER provides Technical Advisory Support to Member States through missions such as this one.

The Algerian Space Agency (ASAL), the Romanian Space Agency (ROSA) and the National Observatory of Athens (NOA) are UN-SPIDER Regional Support Office.

Mission dates: 04/03/2020 to 06/03/2020

Upon the request of the Ministry of Territorial Administration (MINAT), Government of Cameroon, UN-SPIDER carried out a week-long Institutional Strengthening Mission (ISM) to Yaoundé from 15 to 19 July. The mission aimed to strengthen the capacities of the Department of Civil Protection (DPC) of Cameroon in using space-based information in all phases of the disaster management cycle. It was the third UN-SPIDER mission to Cameroon after a Technical Advisory Mission (TAM) in 2011 and an Institutional Strengthening Mission (ISM) in 2012, the latter including a training course on “Remote Sensing for Disaster Management”.

Mission dates: 15/07/2019 to 19/07/2019

Data Source

Global Tailings Portal (GRID Arendal)
Publishing institution: GRID Arendal
Publishing institution: Joint Research Center, European Commission (JRC)
GIS Malawi is a webmapper which provides various vector and raster layers covering a broad range of topics including natural hazards.

Recommended Practices

Floods and landslides are the first and fourth most frequent disasters around the world (Petley, 2012). There are several examples of downstream flooding caused by massive mudslides where rapid mapping is an indispensable tool for supporting disaster management activities by civil protection authorities. Since July 2014, the Copernicus programme of the European Union has been providing free-of-charge access to Sentinel-1 radar data coveirng the entire world. This allows for the exploration of new applications to strengthen hazard monitoring and disaster mitigation activities. This UN-SPIDER...

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