Arc changes in arid area rivers (Case study: Qomrood river in Iran)

Qomrood river is one of the rivers that located in arid and semiarid area which has a seasonal fluvial. The river is faced many changes, because of floods or natural- human factors. This study, as a geomorphologic study, tries to survey and identify geometric changes between Kocherey dam and 15-Khordad dam. The study method is a mix of library research and field studies. In library method all papers in journals and sites that related to this topic were collected. In field studies, the data were collected through direct and indirect (satellite image) observations. For this goal, TM (1989), ETM (2000) and IRS (2009) satellite images were used. Accordingly, the tree central lines belonging to different periods of study were extracted. Then these lines separated to 6 parts with emphasize on geological and geomorphologic base. In order to change detection, fitted tangent circle model was used. This research showed that the curves of the river face to decrease, while in some parts that are located on harder geological segments, or always have water, face to increase. It means in these parts all curves and meanders are more than previous. Sinus numerical coefficient in all intervals indicates approximately 1.5 that indicates the average sinus condition of the river at present intervals, and this factor has not changed in these 20 years.