Recurring lanslides and flood damage in Himalayan states need long term solutions say experts

GG News Bureau
New Delhi/Dehradun/Shimla July 29th. A Geneva based global body working for better and safer roads worldwide has expressed deep concern at repeated loss of life ,landslides, flooding, rock fall, areas being cut off and chaos in the road network and infrastructure in the Himalayan states of Himachal Pradesh, Uttarakhand and Jammu and Kashmir in the country for last several years during rains, and has stressed the need of adopting time tested sustainable solutions including Zoning maps of landslides, floodplain mapping and taking flood proofing measures.
“It’s high time that we used tested sustainable solutions and ecologically proven techniques for avoiding flood related disaster each year and also turn to apt investigative tools in determining causes for failure each year . Depending on the causes, proven technologies that meet specific needs have to be adopted so that the State which has borders with other countries has all weather roads and sustainable infrastructure” said K K Kapila, President Emeritus, Geneva based International Road Federation (IRF)
“Worldwide to avoid loss of human life and damage to infrastructure Flood-plain Mapping Programs and zoning of landslide an rock fallprone areas are carried out. This is to generate and provide information to help minimize damage in flood, land slide and rock fall prone areas. The floodplain mapping also known as ‘Inundation Mapping’ is done with the help of remote sensing and ground level river data. This helps in knowing in advance which areas will come under water for every inch increase in river level above danger mark,” said KK Kapila.
“With the help of floodplain mapping, zoning of landslide and rock fall prone areas impact of damage to humans and property floods can be minimized by not allowing habitation and development in these areas, adopting an optimum combination of structural measures such as large storage reservoirs, detention basins and embankments and non-structural measures like flood forecasting, flood plain zoning and catchment area treatment.” He added.
The experts also belived, there is a need to use non-destructive and least invasive techniques to build roads in the state.and a quick stop-gap approach in rebuilding the infrastructure cannot be a solution.
Re-engineering and building the road infrastructure in a step-by-step method using non-destructive and least invasive techniques is the need of the hour. We have to sieve out the best of our past experiences and adopt state-of-the-art non-conventional techniques and propose the appropriate sustainable solutions,” added Kapila.
The experts were of the view that as a first step a detailed subsurface investigation of the affected areas should be carried out. “Non-Destructive Testing (NDT) is an integral and important aspect of subsurface investigations which is recommended, despite a significant school of thought that does not believe in the efficacy of such investigations in the Indian conditions which is a myth. NDT reduces the cost and time of subsurface characterization when carried out along with appropriate validation with invasive techniques. The best tools in the NDT category for hill roads will be Seismic, Electrical Resistivity (ER) and Ground Penetrating Radar (GPR). The GPR is very useful in subsoil investigations and offers concrete characterization of different layers, besides pavement structure integrity.
The experts opined that while planning and designing the rehabilitation of the affected roads, it needs to be remembered that the outer and lesser Himalayas comprised of unstable strata owing to the young, folded mountains and these sections of the Himalayas have very weak to poorly cemented sedimentary rocks that lack inherent strength. Consequently, cutting of slopes in such ranges and strata, regardless of extreme precautions and environment-friendly techniques that are least invasive, does not guarantee adequate protection to the road foundation or the slopes; blasting, which is used as the faster and an economical method of road construction, should be avoided.
“In the recent projects for four-lane and six-lane construction of of roads undertaken by the National Highway Authority of India (NHAI), the hill cutting and widening works has been done using a combination of excavators, road headers and breakers. This minimizes the extent of damage to the hill slopes and strata and in combination with remedial measures such as shotcreting with wire mesh and rock bolting, use of rock fall nets, concrete cladding, and most important proper diversion of surface runoff through catch drains, chutes and toe drains on berms stability has been provided to the slopes,” said Kapila.
Ideally the best way to develop roads in hills was using tunnels and connecting viaducts. This minimizes the disturbance to the existing hill slopes.
“One of the best examples is the Kalka-Shimla Heritage Rail the alignment of which comprises 103 tunnels crossing geologically weak strata. Despite being over 100 years’ old, this rail line had been closed on rare occasions indicating the robustness of the alignment in penetrating slopes in geologically competent formations and tunneling when such formations are unavailable. However, the economics often restricts development of such costly but far more permanent solutions. Thus, it is time that we adopt alternative technologies for our structures,” he added.
Kapila said another area for adopting alternative technology was the use of emergency bridges like Acrow and bailey bridges where bridges are immediately required in Uttarakhand. Modern emergency bridges though costlier, give the advantage of two-lane traffic and allowing heavier loads that match permanent bridges designed for National Highway requirements and in an extremely short time frame, thereby giving early relief and restoring commercial activity which is very important in a state where tourism is a major facet of its economy.
The Authorities were of the view that devastating landslides in Himachal Pradesh need more intensive scientific studies and engineering measures focused on the problem. As per the first step, it will be necessary to prepare zoning maps of landslides and rock fall prone areas through geological and geo technical studies. It said that landslide prone areas should be avoided while locating new settlement or buildings, and those, which are already occupied, should either be resettled, or protective measures undertaken based on expert advice.

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