The Analysis of the Form of the Channel and Its Geomorphological Evidence of Changes Fundamentally and Functionally (Case Study: Zab River, between Mirabad to Brisu)

摘要

Zab River is one of most prominent phenomena resulting from morphotectonic and morphodynamic dynamism in Sardasht township. Area study is part of this river between Mirabad to Brisu with 50 km distance. Regarding research practical and fundamental goal, firstly tectonic study of area, especially mechanism of main fault of region (Piranshahr) was studied through geology maps, then other variables such as discharge and sedimentation were investigated through statistical analysis. In the next step, channel was studied in relation to research final goal (channel changes and its evidence) through aerial photos, ETM and IRS satellite images, topographic maps, as well as field survey with comparative approach of temporally and locally since 1955 up to now.Results indicate that dominant pattern is meander with sinuosity over 2 as well as historical abandoned meander beds with insignificant changes in reach I, channel temporal changes have been from east to west and gardens and farms, especially in DohezarVally had been threatened, there was descending trend in braided pattern with lesser braided index in reach 2 with evident change in current anabranch pattern to braided in studied time period in reach 3 and evident change in channel path in upper partof the same reach. In lough reach, dominant pattern is confined meander and only in Guman some minor changes were seen. Research findings indicated that tectonic and active fault of Piranshahr with special lithology, have created tensional basins like Kalweh Plain and echelon trend and have led to placing Zab channel in its lower section and it has determined general shape of channel. It has led to current dynamic features (discharge, sedimentation) and their actions in systemic relation to initial factor causing to dynamic changes. Meanwhile, human intervention has also impacted on changes severity and channel threats.