Landslides have been known to be major tragic incidents that can cause deaths. This article serves to provide some of the important facts and information about landslides.
What is a landslide?
A landslide occurs when rock, debris and other geological material flow down a hill slope in a dangerous manner. A landslide may occur in abruptly or it may occur gradually with warning signs. Sudden and rapid landslides are the most dangerous as people do not get sufficient time to take shelter or safety precautions. The landslides movements have been categorized into the following five categories:
This movement ranges from rapid to extremely rapid landslide and the descent process ends with a rapid and catastrophic free fall. These falls are caused by natural phenomena like earthquakes.
This type of landslide is caused by the fracture patterns in the rocks. The rock causing this type of landslide just tilts forward without collapsing. The topple landslide is also characterized by forwarding rotation of rocks around a pivot point.
This landslide is the most dangerous because the flow becomes slurry due to the high-water content present in the slope material.
The slide landslide is the most common cause of landslide and the material moves with a moderate rate in either rotational or a translational motion.
This landslide is characterized by lateral spreading of the slope material over a flat terrain.
Causes of landslide
Landslides mainly occur along planes of weakness that are parallel to hill slope. A landslide can be caused by both, natural phenomena as well as human activities.
Natural causes include:
- Climate changes that affect the stability of the slopes
- Earthquake vibrations
- Volcanic eruptions
- River erosion that causes the undercutting of hills and cliffs
- Prolonged rainfall or seepage that elevates the pore water pressure in the slope material
- Rapid melting of snow
Human causes include:
- Modification of natural drainage systems
- Modification of natural terrains for construction of transportation systems
- Mining activities
- Vibrations caused due to blasting, explosion and traffic movements
- Pipe leakages within the water supply system and sewer reticulation system
- Displacement of rocks due to excavation
- Clearing of forests or any other vegetation
A landslide can also be caused due to a combination of several of these factors. Some slopes are more prone to landslides whereas others are less susceptible. A number of factors trigger landslides but the catastrophe occurs mainly depends on the underlying bedrock and soil in addition to the geometric and the configuration of the slope. Additionally, ground-water conditions also play a major role in causing landslides.
Effects of landslide
Landslides can be catastrophic because they cause irreparable damage to property along with human loss. Moreover, a landslide can impact the quality of life by destroying water supplies, sewage systems, transportation networks, railroads, forests, fisheries and various other natural resources. Landslides also affect economy negatively because a huge budget is required to repair the damages caused by landslides. Many people lose their livelihood when catastrophic landslides destroy forests and cause water pollution that kills fish stock. Besides repair structures, victims as well the authorities have to incur medical costs. Considerable amount of money is spent in conducting geo-technical studies to assess and stabilize the afflicted areas.
Some signs of incoming landslide
It is always safe to pick up on any signs that are good indicators of an impending landslide. Following are some of the indicators that must be watched out for:
- Water gaps in places that are not usually wet before. One can see seeps or saturated ground in these places
- Presence of cracks in the roads, walls, footpaths and other concrete structures
- Sudden alteration of water level in rivers or stream
- Sudden decrease in a river’s water level during a rainfall
- Strange sounds, such as: rock scrolling or trees cracking, are strong indicators of moving debris
- Soil erodes away from foundations
- Cracking and tilting of floors and platforms
- A sudden increase in humidity may also be a sign of an incoming landslide. Newly installed windows and doors turn sticky due to a sharp rise in humidity
- Damaged water pipes or broken underground equipment and utilities
- Tilting of house structures like patios and decks
- Sunken roadbeds
- Increased turbidity in water bodies
- Leaning electric or telephone poles and offset fence lines
It is advised to signal a red alert when locals spot any of these signs in landslide-prone areas.
6 ways to be safe in an unexpected landslide
People need to follow the instructions listing below for staying safe and secure during an unexpected landslide:
- Take shelter under a sturdy and large object if you are staying indoors. Alternatively, you can hide in a place that is strong enough to protect you from crumbling structures. Do not come out until the landslide has decreased.
- Stay awake and alert while taking shelter inside the house. Listen to battery-operated radio or television to receive instructions and alerts from government authorities.
- Evacuate your home if authorities inform that your safety is at stake. You may return if you are authorized to do so and it is advisable to return home only during broad daylight
- Rapidly move away from the path that is bound to be affected by a landslide. Avoid standing near trees, electrical lines, utility poles and river banks.
- Tale extras precautions while driving in an area which is being affected by a landslide. A landslide may wash away bridges or overtop the culverts. Moreover, it will be dangerous to cross flooding streams. Roadside embankments are more susceptible to landslides. You must immediately turn around and drive away from the area after receiving a red alert. Careful look out for collapsed pavement, fallen rocks and other debris that may cause accidents.
- Contact emergency services if you need help. Make efforts to rescue trapped or wounded people if you are safe.
Landslides can be devastating because they occur suddenly, move rapidly and travel over a long distance. Even though they are difficult to predict, landslides are known to send out warnings even before they occur. It is wise to pick up these signals and follow safety protocols to minimize the negative effects of a landslide. Authorities always stipulate that people familiarize themselves with warning signs and follow an emergency plan in case of disaster. Housing communities residing in landslide-prone areas must ensure safety by meeting periodically and practicing safety protocols. Ultimately, everyone must remember that chance favors only the prepared mind.