the assessment of rock fall hazard in roudbar-rostam abad free way

introduction one of the factors affecting in the control of environmental hazards, is the stability of the structure landforms. human activities especially in the case transportation, and also the need to expand it in different areas, can significantly affect on the region geomorphologic structures and causing high damages on life and financial. as a result, human activity can operate as a factor in change geomorphic systems. in this relationship, the semi-arid mountains terms of having topography, climate and vegetation conditions, are most sensitive areas due to changes of human interventions. roads and communications networks are one of the important parts of landscape and there is a symbol of human degradation in landscape. in this research trying to create the relationship between the situation geomorphologic of region and construction the rudbar - rostam abad freeway with the mass movement, particularly rock fall process, in order to analyze the geomorphologic responses of region. the objective of this research is evaluation and classification of rock fall hazard in the rudbar - rostam abad freeway that has been done with quantitative analysis of the efficient criteria for the occurrence of this phenomenon, so that in the past has happen numerous examples in this road.. study area the study area is a section of rudbar - rostam abad freeway in the sefidroud valley. this range is part of the geomorphology unit the western alborz. according to the climate data, vegetation cover and geomorphologic resource, the climate of the region is semi-arid. sefidroud valley in the divisions of geomorphology units is natural boundary the alborz and talesh units also this valley caused by the river erosion along the talesh fault. material and methods in this research remote sensing data, topographic and geologic maps and data results of field surveys was used for the preparation land use map and analytic network process model have been used to analyze the occurrence of rock falling. this model (anp) is used as a way to weighting, paired comparisons and analysis of grading the rock fall occurring processes in the study area. this research done in the following steps: first, determine criterions and characterize the clusters, this step was to determine the factors associated with rock falling processes and 8 main element involved in the problem according to the similarities subject were divided into the two clusters of environmental features and natural hazards. second, the relationships and dependencies between the elements have determined. in this stage the questionnaire and dematy l process was used and results were processed. the third step is creating connections between clusters and elements that were performed in the super decisions software. the fourth and the main stage of the model is weighting and pair comparison between elements and values, and paired comparison will be base on network analysis and criterion control. pair comparisons between elements were performed by using a questionnaire and after determining the final value of each comparison, values and weights obtained from the questionnaires were transferred to the super decisions software. finally, using these weights, the finals weight and coefficient of research through the processes of super matrix and it normalizations by the weight of clusters were calculated. the last step, is involves the classification of layers and finally provide map the risk of rock falling with using the gis software. results and discussion analyze the maps obtained indicates whatever the slope is greater, the risk of rock falling increases and the north slopes is most relevant of aspect for the rock fall. also the wasteland has greatest risk of rock falling and then farming lands and the riverbank are placed in the next classes. the geology information indicated that volcanic rocks, the mass rocks and los are most prone areas for rock falling risk and lands alluvial and sediments of sand and conglomerates are placed in the next rankings. also, by reducing the distance from the faults, road and streams, the possibility of rock falling will increase. in addition, with increasing of precipitation the risk of rock falling rises. thus a large part of the road is located in the range with high risk of rock falling. conclusion essentially, construction of road in mountainous regions is causing destruction of the ecosystems. according to the findings of this research and zoning the degree of the rock fall risk and field surveys, more of this road is matches with the high-risk zones. the research results, in the form of map zoning the rock fall rick, indicated that the areas with high degree of risk the rock falling in terms of the land use criteria were of the type wasteland and in terms of climate are in semi-arid mountain areas. moreover, areas with the higher-risk have a greater percentage of the slope. therefore according to the reasons been said this area is a high-risk zone in the management of road. using the results of this research can be help to planning the environmental hazards on the rudbar - rostam abad highway for prevent the damage of life and financial including these actions can be pointed to the stepped slopes with the high risk and construction the metal tours in areas with a high degree of risk especially in the volcanic rock and mass units.