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.

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

• 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.
• Saturation by Water: Rainfall or snowmelt causes the ground to become saturated. 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, creating favorable conditions for landslides.
• Tectonic Structure: Layers dipping parallel to the slope, fractured (jointed), and 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 warm winds can saturate the ground and initiate landslides.
• Human Activities: Road construction, mining, deforestation, and improper use of sloping land disturb natural balance and create conditions conducive to landslides.

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

• Slides: Occur when large masses move downslope by sliding over a slippery surface, often prepared by water. Example: The 1950 Trabzon-Sera Landslide.
• Rotational Slumps: A type of landslide in which blocks detach from a slope in a rotational motion and move along a concave surface. These commonly result from erosion of the slope base by rivers or waves. They can form backward-sloping surfaces and small lakes.
• Soil Creeps: Occur when superficial deposits or debris layers become saturated with water and begin to flow slowly. They exhibit a flow-like movement but are not as fluid as mudflows.
• Mudflows: Rapid and dangerous mass movements caused by excessive rainfall or sudden snowmelt, resulting in the flow of mud and debris like a stream.

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. Furthermore, 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 terrain. In addition, loss of soil fertility increases the rate of erosion, which negatively affects ecosystems in the long term.

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 vital role in preventing landslides by anchoring the soil in place. On sloping agricultural land, terracing and plowing parallel to the slope prevent soil movement. Additionally, early warning systems should be established in landslide-prone areas, and cracks and seepages on slopes must be regularly monitored 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.

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