Landslide Hazard Zonation Map (LHZM) of Kohima courtesy KMC golden jubilee souvenir
Convenient to blame it on geography, landslides have become a routine trouble for Nagaland State with the last few years seeing a sharp increase in their number especially along the vital road link to the State Capital at the old Kohima Municipal Corporation (KMC) dumping area. Whether it is the bad weather and geography or our roads are constructed badly and inappropriately designed, since Statehood in the 1960s successive State governments have been confronted with this old problem of landslide.
Temporary quick fix solutions are being given but the scene is repeated every year with no permanent solution. The risks have been high and so is the cost of repairing the damage. This year again, one can already see the signs of a disaster waiting to happen.
Quick fix solutions proving to be
high on cost & risk, low on reliability
Speaking to the Morung Express, G.T. Thong, Professor of Geology with Nagaland University, said that in the year 2007 the National Highway Authority of India wanted to resurvey the NH29. They decided that the Jotsoma road could be an alternative. The steep nature of the hill was to be cut by adding more curves. The road construction was started but it ran into some problems and all the half done work is now covered by debris.
It is pertinent for every developing town to have a Landslide Hazard Zonation Map (LHZM). According to reliable sources, there was a tender floated in 2005 for the same purpose. This project had a budget of Rs Seventy Five lakhs. The source disclosed that the tender was picked by some big contractors and the result (as usual) was a complete disaster.
G.T. Thong informed that on realizing the need for a Zonation map, he completed a LHZM under Space Application Center Branch of Indian Space Research Organization in the year 2006. After completion, all Departments were invited to a presentation of the ‘Hazard Potential of Kohima’. Unfortunately only a few turned up; proof enough that we are simply not interested. The Professor also added that a few years back when the area around Mezhur started sinking, he checked the Zonation Map and realized that the area was highlighted under the ‘high hazard area’.
Coming to the topic of the landslide area at the KMC dumping area, G. T Thong disclosed that contrary to popular beliefs, the garbage dumped there has not led to the degradation of the land but rather it is the make up of the rocks and also human activity and interference with nature, which is to be blamed. Kohima is primarily made up of two kinds of rocks namely Barail Sandstone and Disang Shale. While mountains like Japfu are made up of Barail Sandstone, the KMC dumping ground is made up of the Disang Shale.
A characteristic of the Disang Shale is that when water enters the rock, after a period of time it breaks and on weathering forms fine dark clay. This clay on being saturated loose their shearing strength. Any traveler would see that the clay around the landslide area is dark almost black in color. Evidence that the Disang Shale has finally weathered to fine clay!
However one also has to take into the surrounding paddy fields. These fields trap water for 2-3 months and this leads ‘pore water pressure’ to escape slowly and seep through the land gradually making it unstable. A preventive measure would be removing the paddy field around this area completely; no doubt a harsh but much needed step. It may be mentioned here that in 2006, the LHZM indicated the KMC dumping area under the ‘very high hazard zone’ but preventive steps were never taken, resulting in the disaster now. Temporary quick fix solutions are being given but the scene is repeated every year with no permanent solution. The risks have been high and so is the cost of repairing the damage. This year again, one can already see the signs of a disaster waiting to happen.
Quick fix solutions proving to be
high on cost & risk, low on reliability
Speaking to the Morung Express, G.T. Thong, Professor of Geology with Nagaland University, said that in the year 2007 the National Highway Authority of India wanted to resurvey the NH29. They decided that the Jotsoma road could be an alternative. The steep nature of the hill was to be cut by adding more curves. The road construction was started but it ran into some problems and all the half done work is now covered by debris.
It is pertinent for every developing town to have a Landslide Hazard Zonation Map (LHZM). According to reliable sources, there was a tender floated in 2005 for the same purpose. This project had a budget of Rs Seventy Five lakhs. The source disclosed that the tender was picked by some big contractors and the result (as usual) was a complete disaster.
G.T. Thong informed that on realizing the need for a Zonation map, he completed a LHZM under Space Application Center Branch of Indian Space Research Organization in the year 2006. After completion, all Departments were invited to a presentation of the ‘Hazard Potential of Kohima’. Unfortunately only a few turned up; proof enough that we are simply not interested. The Professor also added that a few years back when the area around Mezhur started sinking, he checked the Zonation Map and realized that the area was highlighted under the ‘high hazard area’.
Coming to the topic of the landslide area at the KMC dumping area, G. T Thong disclosed that contrary to popular beliefs, the garbage dumped there has not led to the degradation of the land but rather it is the make up of the rocks and also human activity and interference with nature, which is to be blamed. Kohima is primarily made up of two kinds of rocks namely Barail Sandstone and Disang Shale. While mountains like Japfu are made up of Barail Sandstone, the KMC dumping ground is made up of the Disang Shale.
A characteristic of the Disang Shale is that when water enters the rock, after a period of time it breaks and on weathering forms fine dark clay. This clay on being saturated loose their shearing strength. Any traveler would see that the clay around the landslide area is dark almost black in color. Evidence that the Disang Shale has finally weathered to fine clay!
Speaking to the Morung Express, Er. Tarachu, Assistant Director, Urban Development, was of the view that even if a permanent landslide solution is technically possible, it is doubtful if it can be economically feasible. The engineer also added that since the dumping area has been shifted, the land should stabilize in a few years provided the paddy fields are removed. However the engineer also added that our poor drainages or blockage of the natural course of water by humans are one of the causes of landslides in settlements.
As all National Highways are under the care of the Border Roads Organization, the Morung Express also spoke to Mr. Hakan Singh, Assistant Executive Engineer, BRO, who informed that this year the situation is particularly bad because the landslides are taking place at twelve to fifteen places in a single day. “We are working day and night and all our resources have been put to maximum use. Each slide point has its own difficulties, there cannot be one permanent solution for all landslides and we are dealing from case to case”, stated the Engineer.
To add to the confusion of our landslide affected National Highway, a reliable source who wished to remain anonymous informed that there are talks for ‘four laning’ the NH29. Talks are being held between the Ministry of Surface Transport and the National Highway Authority of India. The executing authority though has not been decided on. The source also informed that only a ‘two lane’ is advisable for a highway like the NH29. More laning will only contribute to the woes of the NH29 as it falls on land that is unstable and subject to constant landslides.
As all National Highways are under the care of the Border Roads Organization, the Morung Express also spoke to Mr. Hakan Singh, Assistant Executive Engineer, BRO, who informed that this year the situation is particularly bad because the landslides are taking place at twelve to fifteen places in a single day. “We are working day and night and all our resources have been put to maximum use. Each slide point has its own difficulties, there cannot be one permanent solution for all landslides and we are dealing from case to case”, stated the Engineer.
To add to the confusion of our landslide affected National Highway, a reliable source who wished to remain anonymous informed that there are talks for ‘four laning’ the NH29. Talks are being held between the Ministry of Surface Transport and the National Highway Authority of India. The executing authority though has not been decided on. The source also informed that only a ‘two lane’ is advisable for a highway like the NH29. More laning will only contribute to the woes of the NH29 as it falls on land that is unstable and subject to constant landslides.
