بررسي نقش پويايي جريان هاي واريزه اي در تغيير بستر و آرايش جريان هاي رودخانه اي در نواحي كوهستاني

On The role of debris flowʹs dynamic in change of channelʹs bed and stream flow patterns, in mountain regions

The study area is located in the north -western slope of Sabalan and northern slope of Gushe Dagh(38° 15ʹ -38° 30ʹ N ,47° 00ʹ - 47° 38ʹ E ) .This region ,is mainly formed of new volcanoic rocks. Bedrock is generally covered by coarse regolith, debris and colluvials .The accumulation areas of large debris flows and forms large debris fans (up to several meters in diameter) on bedrocks, show that this bedrocks are suitable to the derived debris. As a result of suitability of these rocks to forms of debris, associated with favorable climatic condition and present of snow patch most of time, debris flow of the study area is active. The debris situated often in valleys and located in the course of 2 and 3 order streams. These debris, gradually by different factors, for example, the occurrence of flood, moving and transporting by streams and rivers to long distances. The debris deposition on foot of valley wall is a reason for changing of the river flow pattern and then a cause for cut off of valley in other side of valley. The debris flows in study area, have special characteristics, because of existence of topographical factors and morphogenesis. The length of debris flows in the study area is longer than its width .This rate in difference of altitudes is 1:3 to 1:5.This ratio in old debris flows is great and in present debris flows, is small. The results of statistical analysis show that, the role of the depth of channels, in the growth of the length of debris cones is remarkable.