Morphological Evolution of Euphrates River Cross-Sections in Central Iraq: Response to Streamflow and Sediment Load Variability

Abstract

In recent years, the Euphrates River in Iraq has experienced a noticeable change in its morphological system. The presence of sediment has created some problems in spite of rehabilitation and maintenance process have been put into practice. Therefore, the aim of this research is identifying the morphological evolution in a part of Euphrates River as response to streamflow and sediment load variability due to climate change. To this end, a field survey was conducted along a part of Euphrates River in center of Iraq start from station 605+554 km northern Al Hindiyah Barrage and extend about 25 km downstream until station 630+00 km. Approximately 40 cross-sections were surveyed along river reach with distance between one cross section and another from 0.4 to 2 km. The meandering changes and river migration were estimated with support of Satellite images, besides provided maps and aerial photographs to investigate which river segments that remained steady or changed between 2019 and 2022. The field surveying was included of explore morphologic manifestations of channel such as; meanders, bends, bars and islands and measured the change in geometry shape of selected cross sections. For analysis, a comparison was done with historical field data approved in 2019. The results have indicated that the channel has multiple morphology course of river consists of straight, curved and braided parts and the curvature occur according to the stage of the flow. The average width of displacement is changed between 130 m and 930 m and the variation in centerline distance due to variations in the radius of curvature caused by the internal arc's reduction 880 m and 2035 m. The river is varied in the ratio of sinuosity SI between 1.005 and 1.149 "straight" and "winding" sections; and there is one meander formation the maximum percentage of sinuosity 1.62. The geometry of cross sections, sediment and water conditions are mightily connected and varied relatively over the time scale. The variation in shape has associated with constructing floodplains, riparian vegetation, and boundary conditions. Besides, the quantity of sediment that input river reach. Several factors have helped to widen floodplains over along time of centuries like; flood deposition, river flow, presence of plants, branching, bends and meanders, and the presence of river islands. The results of survey can have important effects on the development, operation, and maintenance of river basin for sustainable use in an environmentally and economically sound manner.