land slide control mechanism
The need is the modelling and pin pointing of the of the risky areas. Categorization based on various parameters and planning the approach well in advance is the only way to get rid of such calamities.
Rainfall triggered slope failures are quite common in different geological, topographical and geohydrological environments but sometimes the slow and steady percolation process soften the region and can result to the catastrophic outcome. The catastrophic landslide in Sindhupalchok District was also similar which washed away many life and assets. We can’t stop the natural calamities but can take precaution in advance to reduce its effect. According to tremendous research, slope failures are attributed to a number of influencing parameters. A astute understanding of the geological environment as well as proper evaluation of the geotechnical and geohydrological characteristics of soil and rock masses is the key for a slope stability assessment. In order to prevent the big-scale landslide, we shouldn’t overlook the small landslides which has occurred. The proper investigation should be carried out, which should involve aerial photo interpretation, surface mapping, subsurface investigation, in-situ hydraulic conductivity test of soil, in-situ strength test of rocks and laboratory analysis of soils and rocks. Before this, we also must understand what really is landslide and its causes and its alternatives. Landslide is the condition in which the land get slide from its original state in order to maintain its stability. There are many factors due to which this catastrophic can occurs. This cause includes Geological causes, Morphological causes, Physical causes and Human causes. Normally heavy rainfall, Sheared materials, Jointed or fissured materials, adversely orientated discontinuities, permeability contrasts, material contrasts, Earthquake, working of machinery is included in Geological causes, in the same way slope angle, uplift, rebound, fluvial erosion, wave erosion, glacial erosion, slope loading, vegetation change and Erosion is included in Morphological causes and Excavation, loading, draw-down, land use(houses etc), water management, mining, quarrying, vibration, water leakage, deforestation, land use pattern and pollution are included in human causes. People must be aware of these causes and take precaution for these deeds, this helps to advance our preparedness.
If we review the landslide around the world than many governing factors has been forwarded. Especially in china, landslides did trigger due to strong storm causing 200-300 mm/d of heavy rainfall. In recent years, global warming causes the temperature to rise, snow line to shift, glacier recession and glacier lakes to collapse. These factors are also the triggering factors of large-scale landslides in some areas. In addition, the causation of more than 70 percent of large-scale landslides is closely related to the human activities. The large-scale landslides can be summarized into three types: rock landslides, soil landslides and landslides in debris. The typical geomechanical models of large-scale landslides in rocks and soil must be studied to make advance preparation
In our case, it is somewhat different; there isn’t the case of heavy rainfall and other environmental hassle. The catastrophe has occurred due to the soft and unstable soil condition. It has been concluded that small landslides would occur each year in this area and the consolidation of the road in the catastrophic site had been seen from long time. In spite of all this, the area was not even listed in highly risked area for the landslide. Normally, if we could have taken up the basic precaution in time, we would not have encountered this catastrophic circumstance. Well in advance we should have alerted this area as landslide prone area and the basic preserving attempts should have been imposed. Reinforcing the soil with natural plantation process, avoiding the area for settlements, use of retaining wall in the risky areas etc should have been taken in place well in advance, this would have at least save the life and also would have reduce the risk in ample amount.
If we consider India itself, there are also lots of landslides and flooding that occurs frequently. They have proper diverging canals due to which the effects of the flooding and landslide get reduced. Reacting at the time of catastrophe is not the solution for overcoming the catastrophe but to make a proper plans and strategies in advance helps to reduce the risk. These incidents have really dragged our government attention for planning in advance for these deeds.
Normally, we have many landslide prone areas in Nepal. The proper study and location of those areas must be done as soon as possible. The GIS mapping for those prone areas must be located and also it must be flashed to the public. After the mapping of those areas, the places where the normal engineering application can be done to resist the calamity must be identified and proper solving techniques must be forwarded. The general surface drainage at the upper and middle section of the slopes and subsurface drainage, free flow canals, surface reservoirs at the lower sections of the slopes can be other simple but effective remedies. It is not the responsibility of government solely to take responsibility for the task. Normal engineering approach can be taken up by the local people also with the normal backup from the government. The landslide prone areas must be immediately vacant and alternatives for those areas must be identified and horizons must be provided. Stabilization of soil in the slops by any geotechnical methods must be done immediately to avoid this problem in those areas.
Normally for the bank of big rivers, there is also probability of blocking the way of the river as in this case and for this type of problem, the alternative canal must be constructed which can help in irrigation and also reduce the water scarcity of any area and also the water can be diverted in the difficult circumstance. This not only help to reduce the landslide but also equally will be helpful for flooding and submerge certain area nearby the river site. Mostly, in many developed countries, the alternative canals are constructed in many places with certain distance gap, this helps in tremendous ways. The proper study of this must be done and the work must be forwarded accordingly.
Normally, model preparation and understanding it and using it for tremendous research and development approach helps to bring many innovative approaches to save the area from the calamities. Normally, in Nepal many donations for these deeds are being invested but their effectiveness is still nugatory and the approach has been limited in certain extend only. It is shown in engineering practice that the correct understanding and using of geological and mechanical model are the fundamental keys for the prevention of large-scale landslides.
Whatever the circumstance is, the basic need is the modeling and pin-pointing the risky areas. Categorizing based on various parameters and planning the approach well in advance is the only way to get rid of this kind of calamities. It is also important that we can’t stop this kind of deeds but our advance preparation can enforce us to face these problems with self esteem or reduce the risk. Many training programs for the society and for the people is also importance to bring of its effectiveness in a more concrete way.
The Article is published in The himalayan times, Op-Ed Section, National paper of Nepal
