خطر ريزش هاي سنگي در دامنه هاي شرقي سهند و پهنه بندي محدودههاي مخاطره آميز در حوضه قرنقوچاي

Rock Flow Hazards of in Mountainous Areas of Garangoo Catchment (Eastern Slope of Sahand MlNW of Iran)

Rock flows are frequent natural and geomorphic hazards in semi-arid mountainous regions. Among many mass movement hazards occurring in mountainous areas, rock flows are very frequent phenomena which are- characrerized by their suddenness and difficulty to predict. These phenomena can be attributed both to the development of man-made structures and human impacts in mountainous regions, and have been threats to people who live, work and settele in villages or pass in through mountainous regions and routes. Garangoo catchment, as a semi-arid area (located in eastern slope of Sahand mountain, situated from 46ｰ.27ʹto 47ｰ.42 E, from 36.58ʹ to 37ｰ.44ʹN), is one of largest catchments of Sahand mountain. Rock flow occurrence is extended to the foothills where generally populated areas are located. The management of it firstly requires, the investigation of mechanism of processes induced in rock flows and then zoning of susceptible areas to the hazard events. The aim of this article is to give an overview of 9 factors in the occurrence of rock flow hazards, susceptibility and assessment elements in risk mapping and finally rock flow vulnerability and risk assessment by the use of geographical information systems. For estimation of spatial and temporal distribution of potential rock flows, we used many data and maps, for example, precipitation data, geological data... and digital terrain data in GIS, The empirical approach relies on bivariate statistical correlation between locations of rock flows and factors. The final map, which is produced by ArcView, shows that major parts of the Garangoo catchment consist of volcanic ash, marl and old alluvium, with steep slope at site of 2000 m altitude. The volcanic material (andesite and dasite) especially Miocene volcanic stone, is frequently producing debris and rock segments. These materials are deposited on road surfaces and disturb passengers.