Investigation of morphological changes of estuaries (Numerical simulation of Shalmanrood river with MIKE21 software(

Geometric and morphological characteristics of each river are its main characteristics by which the management planning of the basin and the conservation of natural resources around it is done. Estuaries are formed at the mouth of rivers in a border area between sea and land. Deformation of estuaries due to sedimentation and erosion changes the pattern of river flow. In this research, the hydrodynamic model (HD) is used to calculate the flow rates and velocity and the sediment transport model (ST) is used to calculate the suspended load and bed level. The results of the hydrodynamic model showed that the maximum speed at 17 km of Shalmaneh station (beginning of the third interval) is approximately 4.7 m /s. This value decreases to about 1.5 meters per second as we approach the end of the estuary. Due to the importance of the role of floods in bed changes, the model was implemented using the 25-year flood discharge of Shalmanrood River (355 cubic meters per second) for a period of one year. After that, the river route was divided into three parts and the behavior of Shalmanrud river was studied according to the deformation created in the sections of each part. The maximum amount of sediment in the first part is 0.41 m in non-flood condition and 1.1 m in flood condition. In the second part, sedimentation increases and in non-flood state reaches 0.8 meters and in flood state reaches 2 meters. In the third part, the amount of sediment will be more than the first and second parts. The maximum amount of sediment in this part is 0.53 m in non-flood condition and 1.4 m in flood condition.