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The semi arid mountain ,due to climatical ,hydrological and topographical properties ,represents vulnerable base for the occurrence of landslides.The deep stream bed and streamflow in long beds ,main triggering factors materials wall of valleys to slides events.In study region ,as a semi arid region ,was occurred many landslides ,because these landslides events changing the hydrological properties of valleys and amount of load sediment.In this study ,by using of geological and topographical maps ,sampling of soil and field work ,analysied the valleys landslides.The result of this study show that, all of failures and landslides are related to rate of drainge density ,specials depended to drainage density of deep beds , related to rate the changing of ratio of Ds/Dd ,also related to changing R .When increases the rate of slope angle ,then increases probably of the landslides occurrence on unconsolidated materials .

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The landslide events on the slope of mountains catchment is the result of the activity of many processes and also the effects of many factors, such as litology, slope, land use, amount of precipitation, fault, road and stream. These factors play an important role on the landslide events in mountain region, but in a particular site ,a special factor always plays the major role on these events so that determining of this factor in the prevention action is of great importance .In Garangoo,s catchment, which has special differences in term of litological and geological characteristics and also in terms of the shape of connection between human and environment, the differences in these characteristics ,causes of the landslide events to be different. In this paper, regardeding the distribution of the landslides on nine map layers of the agents, map was event frequency calculated and special factor was selected on triggering of the landslide events ,by using a the determination of special factor method. In the final stage, using Arc/View was zonate the potential vulnerability area with the related landslide events. This calcution and zonation map showed that volcano ash and marl, that old and large landslides have been occurrend over these materials, are favorable areas for the landslides occurrence. On the other parts of Garangoo,s catchment, irrigation planting ,with disturbance outcome on the slope, has become the major triggering factor on the landslides occurrence.

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Natural events and disasters always have a devastating impact on human settlements and incur economic and social effects on societies by destroying buildings and infrastructures. One of these destructive phenomenons is landslide that could damage communities, meadows and forests, communication lines, and monuments extensively in many parts of the globe, especially in mountainous countries such as Iran. Some information is currently available about the morphological cause and effects of some apparent cases. However, the destructive effects of this phenomenon on ancient settlements have not adequately been mentioned. This study examines an ancient landslide by combining data from two seasons of archaeological excavations of Tepe Mehr Ali, located in Fars province, and related interdisciplinary studies. The results of the excavations, geological evidence and morphology of the site indicate that the southern slope of the mound (about 35 degrees) to Balangan River, represent a landslide event leading to the abandonment of this site for some time during settlement periods.