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Landslide risk assessment along a major road corridor based on historical landslide inventory and traffic analysis

Nayak, Jagannath (2010) Landslide risk assessment along a major road corridor based on historical landslide inventory and traffic analysis.

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Abstract:Landslides are destructive and annually recurring phenomena which cause disruption of traffic and fatalities along the road in the Himalayas. They are more frequent along the cut slopes of the transportation routes such as road corridors than on natural slopes. Risk quantification of landslide is one of the major challenges in research because of the uncertainty associated with its occurrence. This study aims at quantifying the amount of direct risk for a part of National Highway 108 (Uttarakhand), based on the different types of vehicles and different landslide types, magnitudes and expected return periods and the indirect risk generated as the loss of profit due to the blockage of the National Highway 108 by landslides. A multi-temporal inventory of landslides was prepared with the help of available BRO records from 1994 to 2008 and using 12 multi-spectral and panchromatic images of IRS and Cartosat. On the basis of field data and signatures obtained from satellite images, 178 landslide events were identified and separated into rock and debris slide with 3 magnitude classes for each landslide type. In total 164 mapping units were generated for the study area for the characterization of landslides. For these 18 hazard scenarios were developed on the basis of 2 landslide types, 3 magnitude classes and for 1, 3 and 5year return periods. For each of these scenarios a Poisson probability model was used for estimating the temporal probability and direct spatial probability was estimated from the area of the landslide with respect to the area of the mapping unit. High hazard for rock slide magnitude III and debris slide magnitude III was obtained as 0.69 and 0.77 respectively in a 5yr return period. The lowest hazard was estimated for debris slides with a magnitude I showing 0.002 probability of hazard. The vulnerability of different vehicles was estimated on the basis of Average Vehicle Density for particular type of vehicle and different magnitudes of landslides with the help of a Poisson Curve. Highest vulnerability of two wheelers, four wheelers and large vehicles was obtained as 0.8, 0.6 and 0.4 respectively for rock slides with a magnitude III. The vulnerability of the road itself was estimated on the basis of the length of the road damaged due to a particular landslide, taking into account slide material accumulation, removing cost and repairing cost of the damage road. Rock slides with magnitude III show the highest vulnerability for road i.e. 0.9. Specific risk to different elements at risk was calculated on the basis of the 18 hazard scenarios for two wheelers, four wheelers, big vehicles and the road itself study with the help of collateral data obtained from the field. Direct risk for different vehicles due to all magnitudes of debris slide was found to be 70000 $ while direct risk for different vehicles due to all magnitudes of rock slide 245000 $. Direct risk of road was found to be 2200000 $ due to rock slide which was quite higher than the direct risk of road due to debris slides i.e.540000 $. Indirect risk in this study was calculated on the basis of road blockage time and loss of profit to various business types in Gangnani, Harsil and Sukhi Top during peak season. The highest indirect risk was observed in religious vendors for both the places i.e.9000 $ in Gangnani and 130000 $ in Harsil and Sukhi Top. This study in a Himalayan road corridor serves as a case example for the assessment of quantitative risk for landslides which can be useful to planners and decision makers in the hill area development.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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