landslides

LANDSIDES

Landslides
Landslides are among the major natural disasters or calamities in the world. In hilly terrains of India, including Himalayan mountains landslides have been a major and widely spread natural disasters that strike life and property almost perennially and occupy a position of major concern. These landslides, year after year, bring about untold misery to human settlements apart from causing devastating damages to transportation and communication network. Landslides, debris fall, debris slide, debris flow, rock toppling etc. cause destruction of slope and ground surface, initiating the change of uncontrolled erosion in the mountain terrains.

FACTORS THAT CAUSE LANDSLIDES
Landslides occur because of the interplay of several factors.
Natural factors
★ Intensity of rainfall
★ Steep slopes
★ Stiffness of slopes
★ Highly weathered rock layers
★ Soil layers formed under gravity
★ Seismic activity
★ Poor drainage
Man made factors
★ Deforestation leading to soil erosion
★ Non-engineered excavation
★ Mining and quarrying
★ Non-engineered construction
★ Land use pattern

Vulnerable houses are those which are situated on:

• Existing landslides area.
• Steep natural slopes.
• Areas in or at the mouths of drainages (such as canyons).
• Houses constructed near foothills.

PROTECTION MEASURES FROM DAMAGE TO BUILDINGS
Site Selection
Landslides generally happen where they have occurred in the past, and in identifiable hazard locations. Areas that are typically considered safe from landslides include areas that have not moved in the past; relatively flat areas away from sudden changes in slope; and areas at the top of or along ridges. Houses built at the toe of steep slopes are often vulnerable to slides and debris flows.
Signs and Warnings
A house located on a hill can detect possible slope failure by watching for these signs:
Doors or windows stick or jam for the first time.
New Cracks appear on plaster, tile, brick or foundations.
Outside walls, walks or stairs begin pulling away from the building.
Slowly developing, widening cracks appear on the ground or on paved areas such as streets or driveways.
Underground utility lines break.
Fences, retaining walls, utility poles or trees tilt or move.
Water or bulging ground appears at the base of a slope.

The potential for landslides and destructive erosion can be greatly reduced or prevented with proper development, sound construction techniques, seasonal inspections and regular maintenance of drainage facilities.