Sahyadri ENews: LXXVII
Sahyadri ENews: I - LXXVII
Frequent Landslides in the central Western Ghats due to mismanagement of ecologically susceptible regions
Lanslides occur when masses of rock, earth or debris move down a slope. Mudslides, debris flows or mudflows, are common type of fast-moving landslides that tend to flow in channels. These are caused by disturbances in the natural stability of a slope, which is triggered due to high intensity rains with the extensive changes in land cover. Mudslides usually begin on steep slopes and develop when water rapidly collects in the ground and results in a surge of water-soaked rock, earth, and debris. Causes are either preparatory (factors responsible for unstable slopes) or triggering causes (events initiating landslides / mudslides). Thus, a landslide is a complex dynamic system with preparatory causes making slopes vulnerable to failure, while the triggering causes initiates the movement. However, each ‘landslide’ characteristically involves diverse processes operating together, often with differing intensity during successive years.
The current Issue (LXVII) of SAHYADRI E NEWS investigates the causes and triggering factors of landslides in the ecologically susceptible Western Ghats region. The main trigger of landslides in central Western Ghats is due to high intensity or prolonged rainfall coupled with the large-scale land cover changes in the ecologically fragile regions. Slope failures are often triggered by anthropogenic activities with a high degree of unscientific developmental activities in vulnerable landscapes. Land use or land cover changes leading to land degradation and make hillslopes more susceptible to instability (or mass movement). The past several decades have witnessed intense disruption of forest cover, for alternative land uses (mushrooming of resorts under the guise of ‘eco-tourism’, mining, quarrying, monoculture plantations, agriculture, human settlements, roads, railways etc.) in mountains and hills with undulating topography. In such cases with the extreme meteorological events, such as high intensity rainfall leads to mudslides or landslides, leading to the loss of life with large scale destruction of property. Risk levels increase drastically in landslide prone areas with the accentuated anthropogenic activities. In addition to the terrain’s geological property like shattered, fragmented and highly jointed rocks and topography like steep slopes, and factors contributing to slope failures are: (i) large scale land use changes leading to the removal of natural forests with native species, (ii) blockage of stream network leading to poor drainage network in the hillocks – due to changes in land cover (removal of vegetation or obstruction of drainage channels / streams and construction of resorts and villa’s hindering the natural flow of water), (iii) destabilizing the slope through the removal of the basal support with steep slopes cut for linear projects (roads, pathways, etc.) and residential buildings near the base of the slope, (iv) changes in rainfall patterns – recurring instances of high intensity precipitation in short duration due to changes in the climate with the global warming, etc.