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When are We Going to Learn!
|by V. K. Joshi (Bijji)|
It is said, that one learns by experience. But when it comes to natural disasters, it seems that our memory is really short lived! In August 1998, the period between 11thand 19th was perhaps the worst for the residents of Uttarakhand. It was during this period that incessant rains brought the hill slopes tumbling down at Malpa and also at Ookhimath.
The disaster at Ookhimath was still worst. It was pouring all over and the severity of rainfall increased from 1th August. Continuous rainfall had soaked the hill slopes, more because of the fact that the terraced slopes, had rice fields, with margins raised to hold water for sowing paddy. Excess rains caused these tiny marginal bunds to give way and channels of water began flowing down the slope. On the other hand, rain kept lashing and further soaking the ground. The higher reaches of this area have dense cedar and oak forests. The rain water there managed to enter the crevices in the rocks widened by the roots of ancient trees. This water froze during the nights and in the day time, it would expand due to heat and chunks of rocks would break off with a plop.
After the first slide, the geologists working in the area had warned the government to take stringent measures to check construction activity in the hazardous zones. The advice went unheeded. On 13th September 2012, Ookhimath area had 212.5 mm rain in 24 hours. The ground conditions were worse compared to the 1998 disaster. The unconsolidated sediments of the past slides were being used for various purposes. When a land is being used, it is bound have humans around. The unconsolidated sediments are quite porous. With the result plenty of water seeped down and the ground became slushy and swollen. With hardly any drainage the pore pressure within the sediments became unbearable and the land mass moved downwards. To compound the matters in Chuni-Mangoli village a drinking water tank of one lakh litre capacity was also damaged. This added to the local woes.
Better drainage facilities in such areas will help in releasing much of the pore pressure. Drainage is even otherwise important on such slopes, as water is the best lubricant for the rock mass and wet slopes pave the way for a landslide. The importance of proper drainage in the mountainous terrains was better understood by the British. The drainage network on the slopes surrounding the Lake is a classic example of the care taken while inhabiting the area. Similarly, the drainage network along Kalka-Shimla Rail track is yet another example to check the slopes from moving downwards. It appears that we know these examples, yet we ignore the importance of developing a proper drainage before heading for a construction project.
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