University of Twente Student Theses


Evaluating protective function of forest against rock fall hazard: a case study of Himalayan temperate forest Uttarkashi, India

Rawat, Ankit (2012) Evaluating protective function of forest against rock fall hazard: a case study of Himalayan temperate forest Uttarkashi, India.

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Abstract:Rock-fall is a common slope failure process in steep mountainous landscape, characterized by rapid downwards slope movement of one or more boulders through free fall, bouncing or rolling. Many mountain forests effectively protect people and assets against natural hazards. This natural slope failure process becomes more concerning with the presence of high vulnerable elements down the slope like roads, transport, buildings, peoples and agriculture land. Their protective effect is, however, not constant but depends on forest dynamics. The main objective of this study is to analyze the role of protective forest against rockfall impact along a road in a Himalayan setting, by means of a dynamic GIS-based modelling approach. This thesis shows that simulation models such as ‘RockyFor 3D’ for investigating the protective function of the forest and for optimizing its management. In present study the rock fall hazard is assessed along the road corridor (NH-108) between Uttarkashi to Gagnani, including roadside residential areas and other infrastructures. The region is continuously under impact of natural hazards occurring due to slope failure, causing societal and economic losses. The efficiency of protection forest, against rock fall hazard depends on the forest stand parameters such as tree density, tree diameter, species composition and spatial arrangement of trees in forest. These parameters directly regulate the energy dissipation potential of trees on collision with a rock mass. The different remote sensing and GIS derived inputs used for present study. The satellite data and other ancillary information are used for two main purposes for field work and preparing for inputs for rockfall modeling. During pre-field work the identification potential rockfall source area were carried out along the National highway 108, using DEM-based morphometric analysis, in order to select proper rockfall site with presence of forest cover as most of the rockfall events on national high 108 are resulted from human activities like road construction, mining , blasting etc without presence of forest cover..The various instrument used during field work are GPS, Haga-Altimeter for measuring tree-height, Laser-distance meter use to locate the distance between trees in a forest stand, metallic tape for diameter measurement etc. The protective effect of forest stand was assessed by quantifying the change in the impact rockfall trajectories between the scenarios of current forest cover and non forest cover for different rockfall site with varying dimensions of boulders. The model simulation shows that lithology in general does not affect the protective function of forest of in great deal. The reliability and quality of input data for proper rockfall modelling were assessed on the basis of observed and simulated rockfall pattern, with spatial distribution of rockfall trajectories, run-out distance and the mean impact height of boulder on the trees. The outcomes of the study showed that the forest stands are effective in mitigating the impact of rockfall hazard. Furthermore, the model also simulated the optimum forest stand density of the protection forest to offer maximum resistance against rockfall hazard. The model also simulated the tree impact height of falling boulders which matches closely with the tree impact height as observed in field condition. This proved the repeatability and transferability of the model in Himalayan settings. Keywords: Rockfall modelling, Protection forest, Rockyfor3D, Uttarkashi, GIS, DEM.
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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