River Capture and its Impact on Fluvial System, Case Study: Baghlar River in Northern Slope of Mishow-Dagh, Northwest of Iran

Baghlar’s fluvial system with it’s two main tributaries (Meshalar and Sisda), is a small catchment (12.8 km2 area) that has situated in southwest of Koshksaray in northwest of Iran. It is one of the fluvial systems in northern slope of Mishow-dagh chain whose development cycle has tolerated excessive changes in recent geological periods. River capture is one of these changes. In this paper, emphasizing on field studies and topographic and geologic analysis, in addition to investigation of effective factors on river capture, consequences of capture are also investigated. Results showed that the present condition in fluvial system is a result of diversion/capture processes and allogenic control mechanisms such as tectonic activities and mass movements. Diversion of Meshalar onto Sisda as the result of landslide occurrence and then capture of Meshalar by another tributary above the diversion point (due to operation of tectonic activities) have been consequences of increasing river incision and changing channel-reach morphology above the capture point, abandoned of segments of previous Meshalar channel, wind gap formation and changes in morphology of Baghlar alluvial fan. Generally, Baghlar fluvial system is a highly dynamic system from geomorphologic processes and sensitivity of different segments of system to allocyclic or outocyclic environmental changes. All these distress the attention to sensitivities in planning programs on such fluvial systems.