Impact of River Valley Shape on Flow Characteristics in Case of Flooding

Saqib Ehsan, Walter Marx


The properties of a river flow strongly depend on the shape of river valley. Especially the magnitude of flooding downstream a dam significantly changes with respect to the shape of downstream river valley. There are different shape parameters of the river valley which could affect the flow through a river. This paper focuses on the impact of valley slope and width on main flow characteristics (discharge and water level) in case of flooding. As a basis for systematic hydraulic analysis, the Jhelum river valley downstream of Mangla dam in Pakistan has been considered. First the Jhelum river valley has been classified according to the available river classification systems and then artificial new valley shapes have been produced by making different changes in valley slope and width with respect to the available guidelines. For all valley shapes, unsteady flow modeling has been carried out by using the model MIKE 11 for different flooding scenarios. The changes in flood routing results of different valley shapes have been analyzed. This study would guide in assessing the behavior of other river valleys in the world with respect to the severity and extension of flooding. The results of this study would also be helpful in planning structural and non-structural flood safety measures for river valleys in Pakistan as well as in other parts of the world.

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