Concept Clarity: Landslides involve the movement of rock, earth, or debris down a slope, often caused by natural events like rainfall or human activities. Key factors include geological conditions, soil characteristics, and water accumulation. Understanding these elements helps in assessing and mitigating landslide risks.
Key Factors in Wayanad Landslide
• Geological Characteristics:
• Fractured Rocks: The Vellarimala region’s geological structure includes fractured rocks. These fractures, or breaks in the rocks, can fill with water, leading to slope instability and landslides.
• Soil and Rock Composition:
• Acidic Soil: Unlike alkaline soils, which are prone to soil piping, Kerala’s acidic soils do not typically form subsurface tunnels due to erosion. In the Himalayas, soil piping can create underground voids that may collapse, contributing to landslides. In Wayanad, however, the landslides are more related to the fractured rock formations and the region’s specific soil conditions.
• Angular Rocks: The presence of angular rocks in the area suggests a history of previous landslides, indicating long-term geological instability.
• Rainfall and Water Accumulation: Heavy and prolonged rainfall can saturate the soil and increase water pressure within rock fractures. In the case of the Wayanad landslide, excessive rain led to rapid water accumulation, causing soil and rocks to slide.
Human Factors
• Unscientific Land Use:
• Tea Plantations: The historical development of tea plantations involved leveling natural gullies and altering drainage patterns, which disrupted the natural flow of water and increased the risk of landslides.
• Construction on River Terraces: Building on river terraces, which are flat areas formed by sediment deposits along rivers, can be risky. These terraces are prone to flooding and landslides, especially when natural watercourses have been altered.
Impact of the Landslide
• Debris Flow: The steep descent from Vellarimala’s high altitude (around 2,000 meters above sea level) to the lower areas of Mundakkai and Chooralmala (900-1,000 meters above sea level) caused a rapid and forceful debris flow, resulting in significant destruction.
• Destruction of Property: The landslide destroyed numerous homes and structures, including a school, as the debris followed the river’s previous natural course, which had been altered either by past events or reduced water flow.
Comparative Analysis with Shirur Landslide
• Wayanad: The landslide was influenced by a combination of natural geological conditions and human-induced factors, with heavy rainfall playing a critical role.
• Shirur: This landslide was primarily caused by human activities, particularly unscientific highway construction, without considering the geological risks.
Conclusion
The Wayanad landslide illustrates the importance of understanding and respecting geological and environmental conditions in land use planning. While soil piping is not a significant factor in this region due to its acidic soil, other geological and human-induced factors contributed to the disaster. Effective management and planning can reduce the impact of such natural events and safeguard communities.
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