Landslides
Landslides can be defined as a movement of mass rock, earth or debris downslope (Cruden, 1991). In literature, the term ‘Mass movement’ is often used but ‘landslides’ is preferred as the term clearly reflects its mechanism. However, mass movement processes include rock creep, debris flow, avalanches, earthflows etc (Huggett, 2003). Generally landslide is the downward movement of earth material under the influence of gravity and occurs once gravity has exceeded the strength of material present (Fookes et al., 2005). There are trigger mechanisms present, such as rain and earthquakes for landslide initiation. It has to be understood that the magnitude of different mass movement processes differ, some may be of high intensity, others not so much. Nevertheless, landslide movements are generally more rapid (Fookes et al, 2005)
Media has the ability to influence peoples perception on hazards such as this, and so has been done. Landslides has become a common phenomenon worldwide causing damage to infrastructure and most importantly human well-being. Yet not many articles focus on the actual morphology of the particular local slope affected etc. It is important to fully understand local scale processes first in order to progress with remediation to ensure safety of the people. Certain steps are needed such as the identification of landslide type, understanding behaviour and controls. I believe educating people on processes affecting their local area can help prevent disasters.
Following are links to landslide events which have occurred post 2013 and any mitigation efforts (Chronologically placed). Some of the events reflect the complex nature of landslides.
1. http://www.irishtimes.com/news/science/heavy-rain-predicted-to-cause-more-landslides-1.1524283?utm_source=dlvr.it&utm_medium=twitter
It is suggested that increasing climate change induced rainfalls are and will be the cause of present and future landslides in Ireland and Great Britain. Which are increasing in number yearly. The key problem of this hazard in Ireland arises due to unstable saturated peat triggered by building work. No mention in this article focus on remediation plans for this problem.
2. http://news.discovery.com/earth/weather-extreme-events/flood-landslides-wreak-havoc-mexico-130921.htm
Heavy rainfall triggered a mudflow leading to more than 101 deaths with many missing in Guerrero state, Mexico . Authorities and government started reconstruction efforts immediately.
3. http://m.weather.aol.com/2013/09/23/typhoon-blows-into-china-kills-33-in-asia/?ncid=txtlnkushpmg00000034&ts=1379951415
http://www.wpbf.com/news/national-news/Landslides-floods-kill-19-in-Philippines/-/8788944/22089376/-/tk1extz/-/index.html?utm_campaign=wpbf25news&utm_medium=twitter&utm_source=dlvr.it
Multiple landslides occurred in the Philippines and China induced from Typhoon rainfall. According to locals it was the first after a long time hit by this kind of deluge. It is important to understand that China and Philippines have mountainous terrains leading to an area at more risk to landslides. Many landslides have occurred in the past in this area, so mitigation is absolutely necessary.
4. However in; http://news.oneindia.in/india/uttarakhand-showed-indias-vulnerability-pm-1318254.html
the Prime Minister of India realizes its country’s vulnerability to landslide disasters from rains. Past events, with there death tolls have raised substantial awareness for mitigation plans to be made.
5. http://minnesota.cbslocal.com/2013/10/05/6-inches-of-rain-caused-mudslides-road-closures-in-winona-county/
Mudslides hit a town within a valley. It is evident that knowledge is present on stream flow through this valley flowing within a creek yet no barriers etc. It is hopeful that this event can pave way for mitigation plans within this area of the USA.
6. http://www.gmanetwork.com/news/story/329637/news/regions/floods-landslides-hit-negros-oriental-amid-heavy-rain
Another set of landslides hit another part of the Philippines (Negros oriental province) amid 12 hours of rainfall. A highway was blocked due to this.
8. http://newsinfo.inquirer.net/509833/more-bodies-being-dug-up-in-previously-unreached-places-in-bohol
A recent earthquake triggered a landslide in central Philippines.
9. http://www.bbc.co.uk/news/uk-scotland-highlands-islands-24565670
A bypass has been closed down several times due to landslides in the last two years. Now it is surveyed for strict prevention.
10. m.bbc.co.uk/news/uk-england-24520851
Due to change in weather, the British geological society are linking geology and weather to produce daily landslide forecasts.
11. http://blogs.kqed.org/science/2013/10/24/forecasting-the-risk-of-earthquake-related-landslides/
12. http://sciencythoughts.blogspot.co.uk/2013/11/four-killed-by-landslide-in-katsina.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+SciencyThoughts+%28Sciency+Thoughts%29&m=1
13. http://www.foxnews.com/world/2013/11/20/12-gold-miners-killed-8-feared-dead-in-guinea-after-being-buried-by-landslide/
14. http://www.globaltimes.cn/content/828931.shtml#.Ut5lcxDFLIU
15. http://www.bournemouthecho.co.uk/news/10894363.Six_beach_huts_damaged_in_Southbourne_land_slip/?ref=rss
16. http://sciencythoughts.blogspot.co.uk/2013/12/four-killed-by-landslide-at-mine-in.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+SciencyThoughts+(Sciency+Thoughts)
17. http://www.bbc.co.uk/news/uk-england-gloucestershire-25557472#?utm_source=twitterfeed&utm_medium=twitter and http://www.bbc.co.uk/news/uk-england-gloucestershire-25573265
Recent disruptions have been caused to transport services causing severe delays
In all events aforementioned, heavy rainfall and seismic activity have been the initial trigger mechanisms for landslides. However, in certain cases landslides can be human induced (see link 14) where excavation can results in instability of slopes leading to catastrophic disasters. Climate change is an argument posed in majority articles for its cause. All articles clearly state the initiation for the particular landslide. Research on landslides have focused on temporal variability, soil and landscape, slope instability and earthquakes (Jaiswal and Van Westen, 2009; Casadei et al., 2003; Dai and Lee, 2002; Keeper, 1984). It is reasonable to suggest that although rainfall and seismic activity is beyond the controlling capabilities of man, hazard and disaster prevention measures can be taken by:
a: Locating vulnerable slopes (Using remote sensing on wider scale and aerial photographs or field activity locally)
b: Measuring stability of slopes (Regular monitoring)
c: Producing mitigation plans
d: Executing plans
e: Educating people (Local people can carry out simple instability tests)
Past events always pave way for new mitigation strategies. Local management is responsible to ensure regular monitoring analysis of such slopes in order to prevent mass loss of life in the future. Such as done by the USGS. This has been made available recently using remote sensing, the following link gives insight on its use to locate fractures in earth where landslides can occur (http://news.discovery.com/earth/weather-extreme-events/giant-landslide-in-alaska-130904.htm). New methods to detect landslides are being introduced and tested to further ensure prevention (http://phys.org/news/2013-10-seismic-network-landslides-broad-area.html). Research is also carried out on prevention strategies (Nakamura et al., 2013; Karnawati et al., 2012; Ahlheim et al., 2009). Regular monitoring is key as slopes that have previously been affected by landslides are still prone to future occurrences. Plans can be made by first understanding morphology, for example the type of earth materials present, are they prone to erosion? are there any features around which may accelerate erosion? steepness of slope? relief? etc. After taking into account these parameters, a hazard map can be made to distinguish sites high at risk.
In future the media should focus on putting the message across of ‘mitigation’. Questions such as, what can we do? what is being done? etc need to be raised and asked. Most importantly, the education for people on such event processes is needed. Nevertheless, It is evident from the timeline above that new prevention techniques have been proposed.
Important:
http://blogs.agu.org/landslideblog/ Is an fundamental blog on landslides. Dave Petley has been working on landslide monitoring and his blogs gives a great insight on recent and previous events and activities.
http://www.bgs.ac.uk/landslides/landslidesAndRainfall.html . Great link for rainfall and landslide data in UK.
http://www.nationalrail.co.uk/service_disruptions/66078.aspx You can stay updated by following transport services.
(USGS)
References:
1. Ahlheim, M., Fror, O., Heinke, A., Keil, A., Duc, N., Dinh, P., Saint-Macary, C. and Zeller, M. 2009. Landslides in mountainous regions of Northern Vietnam: Causes, protection strategies and the assessment of economic losses.
2. Casadei, M., Dietrich, W. and Miller, N. 2003. Testing a model for predicting the timing and location of shallow landslide initiation in soil-mantled landscapes. Earth Surface Processes and Landforms, 28 (9), pp. 925–950.
3. Cruden, D.M., 1991. A simple definition of a landslide. Bulletin International Association for Engineering Geology, 43: 27-29.
4. Fookes, P., Lee, E. and Milligan, G. 2005. Geomorphology for engineers. Caithness, Scotland: Whittles Pub..
5. Huggett, R. 2003. Fundamentals of geomorphology. London: Routledge.
6. Jaiswal, P. and Van Westen, C. 2009. Estimating temporal probability for landslide initiation along transportation routes based on rainfall thresholds. Geomorphology, 112 (1), pp. 96–105.
7. Karnawati, D., Fathani, T., Andayani, B., Burton, P. and Sudarno, I. 2012. Strategic program for landslide disaster risk reduction: a lesson learned from Central Java, Indonesia.Landslides, p. 91.
8. Keeper, D. 1984. Landslides caused by earthquakes. Geological Society of America Bulletin, 95 (4), pp. 406–421.
9. Nakamura A, T Noro, K Maruyama. 2013. Effects of existing prevention works on earthquake induced landslides
10. Eoearth. 2014. Landslide. [online] Available at: http://www.eoearth.org/view/article/154157/ [Accessed: 21 Jan 2014].
Related articles
- Five-fold rise seen in UK landslides (bbc.co.uk)
- Heavy rainfall causes early landslides in Ore. (kgw.com)
- Floods, landslides in Zambales kill 30 (disaster-report.com)
- Serious landslide closes UBC Trail 5 to Wreck Beach (theprovince.com)
- Pedestrians cautioned after landslide creates new cliff face at UBC (globalnews.ca)
- Landslide in Dhankuta, Nepal buries 13 houses (disaster-report.com)
- Death toll in Philippine quake nearing 200 (channelnewsasia.com)
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