Landslide

Landslide is the movement of a mass of rock, soil, or debris down a slope under the influence of gravity. This type of mass movement, common in the Earth’s crust, can occur either rapidly or slowly. Landslides play a significant role in the formation, erosion, and reshaping of landforms.

Image of a landslide. (Pexels)

Factors Causing Landslides

Landslides typically result from the combined effect of multiple factors. The main causes are:

• Slope Gradient: Steep slopes are more susceptible to landslides. Human activities such as excavation, road construction, and fill operations disrupt natural equilibrium and increase landslide risk.
• Water Saturation: Rainfall or snowmelt causes the ground to become saturated with water. Water increases the weight of the soil, reduces friction, and creates sliding surfaces between layers, triggering landslides.
• Rock and Soil Structure: Formations rich in clay, such as marl, flysch, and tuff, are particularly prone to landslides. Clays with low water retention capacity, like kaolin, become slippery even under minimal water exposure, preparing the ground for landslides.
• Tectonic Structure: Layers dipping parallel to the slope, fractured (jointed), or loosely consolidated rocks increase landslide risk. Additionally, slopes formed along fault lines and seismic activity can trigger landslides.
• Climate and Meteorological Factors: Heavy rainfall, irregular precipitation patterns, sudden snowmelt, and föhn-type hot winds can saturate the ground and initiate landslides.
• Human Activities: Infrastructure development such as road construction, mining, deforestation, and improper use of sloped land disrupt natural balance and create conditions conducive to landslides.

Types of Landslides

Landslides are classified into various types based on their movement patterns and the nature of the material involved:

• Rotational Slides: Occur when large masses slide over dry but slippery surfaces. Water plays a preparatory role. Example: The 1950 Trabzon-Sera Landslide.
• Translational Slides: A type of landslide in which blocks detach from the slope in a rotational manner and move along concave surfaces. These often result from erosion of the slope base by rivers or waves, leading to the formation of backward-sloping surfaces and small lakes.
• Soil Slumps: Occur when superficial deposits or debris cover become saturated with water and begin to slide. These movements are slow, exhibit a flow-like character, but are not as fluid as mudflows.
• Mudflows: Rapid and dangerous mass movements caused by excessive rainfall or sudden snowmelt, resulting in mud and debris flowing like streams down valleys.

Consequences of Landslides

Landslides are events that significantly impact both the natural environment and human life. As a result of these disasters, infrastructure such as buildings, roads, and railways, as well as essential service networks including electricity, water, and natural gas, can suffer severe damage. Destruction of agricultural land leads to economic losses and reduced food production. Loss of life and property are among the most serious consequences of landslides. Additionally, blockage of river channels can lead to the formation of new lakes, altering ecological balances. Permanent changes in topography disrupt the natural structure of the land. Furthermore, loss of soil fertility and increased erosion rates negatively affect ecosystems in the long term.

Preventive Measures

Various measures must be taken to reduce landslide risk. First, construction must be strictly avoided on risky and steep slopes, and these areas should not be selected for settlement. Preservation of natural vegetation and reforestation efforts play a crucial role in preventing landslides by anchoring the soil in place. On sloped agricultural land, terracing and cultivating fields parallel to the slope direction prevent soil movement. Additionally, early warning systems should be established in landslide-prone areas, with regular monitoring of cracks and seepage on slopes to detect potential hazards in advance. Preventing rivers flowing at the base of slopes from eroding and weakening the ground is another effective preventive measure against such disasters.

Landslides in Türkiye

Landslide events in Türkiye are particularly frequent in the Black Sea Region. The North Anatolian Mountains, due to high rainfall, lithological structure, and steep slopes, are highly prone to landslides. Provinces such as Trabzon, Rize, Artvin, and Gümüşhane are among the areas where landslides occur most commonly.