The effect of base level changes in bed rivers morphology of Sefidrood Delta area

Bed river may reflect the influences of erosion، tectonics and climate change. A factor which has the most important role in these changes is، the effects of tectonic and base level of estuary. In this study، the role of base level changes in the pattern of the channel bed rivers of Polrood، Shafarood and Karganrood around the Sefidrood Delta has been studied. The aim of this research is that the river beds of the Caspian coastline near the estuary are deep cutting. Purpose is at this paper the role of factors on base level changes and geomorphologic changes of the river beds. Digital topographic maps، aerial photos and geological maps re among physical tools of this research. Detailed field work to obtain the sections and longitudinal profile of river bed by recording their locations using GPS were. Data in GIS environment and AutoCAD software are processed. Also، the pattern of river channel based on the findings and Theoretical principles of classification and finally، the interplay of the Caspian Sea water level fluctuations and tectonic effects Alborz combined with other data and analysis has been. The results show that short-term changes in water level of the Caspian Sea near the mouth rivers (up to 5 km from the shoreline) have been affected. This impact in east of Sefidrood that the Knick is closer to the beach and coastal plain is wider than the West and northwest، is more. On the other hand، the Alborz uplifting against South Caspian Plate subsidence has been effected the drainages and about 10 km distance after leaving the mountains caused deep drainages in this area.