By Khin Maung Myint
AFEW days ago, there was a very fatal landslide at Thaè Phyu Gone village in Paung township, Mon State. According to the latest reports as at 1813 hrs., 11 August, the death toll had reached nearly 70, and the search is still going on. This could be the worst landslides in our country. Landslides used to occur in the mountainous regions, especially in the Kachin, Chin and Shan states. There may be some other places, but as I have no time to research, I may have missed something here. As my intention is to write about the causes behind the landslides and how to protect them, the locations may not count much.
What is a landslide?
A landslide is a geological process where the gravity caused the masses of earth and debris to fall down the slopes of hills or mountains. They can be devastating if they take place in populated areas. Debris flows, also known as mudslides, are a common type of fast-moving landslide that tends to flow in channels. Landslides are caused by disturbances in the natural stability of a slope. They can accompany heavy rains or follow droughts, earthquakes, or volcanic eruptions. Mudslides develop when water rapidly accumulates in the ground and results in a surge of water-saturated rock, earth, and debris. Mudslides usually start on steep slopes and can be activated by natural disasters. Areas where wildfires or human modification of the land have destroyed vegetation on slopes are particularly vulnerable to landslides during and after heavy rains.
The landslide hazard causes severe loss of life, injury, damage to property, destruction of communication networks and loss of precious soil and land. Although the occurrence of landslides is declining all over the world due to greater scientific understanding and public awareness, in many areas the mounting pressure of population at the base of slopes, canyons and unstable borders of plateau have led to an increase in dangers due to landslides. Landslides are universal phenomena, but more than being ‘natural hazards’, they are induced by human activity.
What cause the landslides?
A variety of contributing fac tors are often responsible for their occurrence, but precipitation often plays a major role in failure. Excess weight from accumulation of rain or snow may stress weak slopes to failure. Almost every landslide has multiple causes. In addition to erosion from waterways, glaciers and waves, earthquakes and volcanic eruptions can cause landslides. Human activities can also contribute to landslides. Fierce winds, flooding, downpours and freezing snowstorms blast away at the earth's surface over time, weathering away the former stability of the land, and setting the stage for collapse. Weather, geology, gravity and time all acting together can prove catastrophic when the earth finally gives way, unleashing a sudden, fatal sweep, whether by slide or descent.
Debris and mud flows caused by landslides are rivers of rock, earth, and other debris saturated with water. They develop during intense rainfall, runoff, or rapid snowmelt, changing the earth into a flowing river of mud and sludge. They can flow rapidly, striking with little or no warning at avalanche speeds, faster than a person can run. They can travel many miles from their source, growing in size as they pick up trees, boulders, cars and other materials in their paths.
When a wildfire burns a slope, it increases the chance of debris flows for several years. Although some landslides require lengthy rain and saturated slopes, a debris flow can start on a dry slope after only a few minutes of intense rain. “Intense” rain means a burst of rain at a fast rate, about half an inch in an hour. With debris flows, the rate matters more than total rainfall.
What areas are at risk?
Some areas are more likely to experience landslides or mudflows, including: areas where wildfires or human modification of the land have destroyed vegetation; areas where landslides have occurred before; steep slopes and areas at the bottom of slopes or canyons; slopes that have been altered for construction of buildings and roads; channels along a stream or river; and areas where surface runoff is directed.
From the news photos and video footages from the disaster struck village in this case, it is quite evident that the area immediately in front of hill slope where the landslide occurred was devoid of protective vegetations. The vegetations on hill slopes can protect landslides from occurring to a certain extent. One of the causes of landslides is modification of the land.
The health hazards associated with landslides and mudflows
Rapidly moving water and debris can lead to trauma in people, broken electrical, water, gas, and sewage lines that can result in injury or illness; and disrupted roadways and railways that can endanger motorists and disrupt transport and access to health care.
What you can do to protect yourself ?
How to protect yourself or your property depends on the type of landslide. Land-use zoning, professional inspections, and proper design can reduce many landslide problems but evacuation is often the only way to protect lives from a debris flow or other fast-moving landslide. Never ignore an evacuation order
Before intense storms and rainfalls - Assume that steep slopes and areas burned by wildfires are vulnerable to landslides and debris flows. Learn whether landslides or debris flows have occurred previously in your area. Contact local authorities about emergency and evacuation plans. Develop emergency and evacuation plans for your family and business. Develop an emergency communication plan in case family members are separated. If you live in an area vulnerable to landslides, consider leaving it if possible
During intense storms and rainfall - Listen to the radio or watch TV for warnings about intense rainfall or for information and instructions from local officials. Be aware of any sudden increase or decrease in water level on a stream or creek that might indicate debris flow upstream. A trickle of flowing mud may precede a larger flow. Look for tilted trees, telephone poles, fences, or walls, and for new holes or bare spots on hillsides. Listen for rumbling sounds that might indicate an approaching landslide or mudflow. Be alert when driving. Roads may become blocked or closed due to collapsed pavement or debris. If landslide or debris flow danger is imminent, quickly move away from the path of the slide. Getting out of the path of a debris flow is your best protection. Move to the nearest high ground in a direction away from the path. If rocks and debris are approaching, run for the nearest shelter and take cover, if possible, under a desk, table, or other piece of sturdy furniture.
After a landslide or debris flow - Stay away from the site. Flooding or additional slides may occur after a landslide or mudflow. Check for injured or trapped people near the affected area, if it is possible to do so without entering the path of the landslide or mudflow. Listen to the radio or TV for emergency information. Report broken utility lines to the appropriate authorities.
Conclusion
As discussed above, landslides are the results of depletion of protective vegetations on the slopes, which deprived the protections and exposed the slopes to the onslaught of the rains, strong winds and seismic activities, such as earthquakes. In most countries, slopes that pose risks to people and properties are protected against landslides by a procedure called slope protection. This involve various means: covering the slopes with concrete membranes to protect them against erosions, growing soil retaining type of grass, afforestations, protections against wildfires on the slopes, etc. The general populations living in the risk areas should also be educated to be aware of the causes of landslides, and how to protect themselves. Rapid response teams should be trained and always be on the alert during the incident prone seasons.
Whatever the cause of the landslides, they are linked to the deteriorating climatic conditions, so, the real culprit is the climate change, which in turn is induced by human activities. Thus humans are to be blamed.
References:-
1. Landslides & Debris Flow, fact sheet, www.ready.gov
2. Essay on Landslides: Factors, Types and Methods - Article shared by DK Sinha
3. Landslides and mudslides- fact sheet, www.cdc.gov
