Influential factor analysis in anomaly of drainage network pattern of Nesar anticline (west-north Zagros)

Nesar anticline is located in west of country and in north of Kermanshah province. Pattern of drainage network at each district is under the effect of various factors which has intensive anomaly in Nesar anticline in spite of its low area and this in turn reflects different lithology، tectonic effects and slope changes in anticline. The goal of this research is the recognition of influential factors and degree effect of each factor in anomaly of drainage network pattern of Nesar anticline. In this research، at first in respect to the kind of drainage pattern، the anticline is divided into 6 parts، then lithology، tectonic and topography slope were evaluated and analyzed as main variable. Results show that lithology is the main factor of anomaly of drainage pattern in Nesar anticline. The parallel pattern in hard constructions (lime) and areas of full of slope has taken shape and dendrite pattern has evolved in weak constructions (Gourpi-Pabdeh) and areas with lower slope. Morphometric figures of drainage network are influenced by constructions material and slope level. Age of constructions has no effect in shaping pattern of drainage. Landslide and tectonic interferences are other influential factors in anticline drainage pattern. Tectonic by omitting Asmari and outcrop of Gourpi construction and Pabdeh play main role in shaping dendrite pattern in parts 4 and 5، but in other parts has little effect as displacement and interrupting drainage network by cracks.