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Abstract:
| The slope and the speed of the water current and the amount of drainage are few in the study section (which starts from the new bridge in the area of Kalak north and ends at the village of Safiyah in the south) because the river is away from the feeding areas and the losses due to evaporation, filtration and human consumption, indicating that the river is in maturity. The actual length of the riverbed in the studied section is (8) km and its ideal length is (7.2) km. Thus, the river is classified within the study area as quirky. It has a winding function (1.11) and, depending on the torsions, the river was divided into four sections.The banks of the Alzab – Alkabir River are affected in the studied section by two types of factors that lead to their collapse. Firstly, the natural factors that cause their instability and then collapse such as: rainfall, river load, terrain, vegetation, river torsions, sedimentary characteristics of river components and slopes. Secondly, the human factors and the most important quarries of gravel and sand and concentrated on the left bank of the river to extract gravel and sand which resulted in many of the trenches and cracks affected the stability of the banks and changed its natural appearance, in addition to agriculture on the banks as fertile areas and good for the cultivation of various crops, which caused the deformation and change of banks and made water flow easily through the seasons of the flood.The river banks consist of clay stone, sandstone, shale, conglomerates and soil; as well as modern river deposits (gravel, sand, silt, mud). Three types of river banks collapses were identified in the study section: Alcove – shape failure, Toppling – shape failure and Mass – shape failure.Key words : Alzab – Alkabir River, Geomorphology of the river, the shape of the stream, the components of the banks, the collapse of the banks. |