Fundamentals of mathematical river flow modelling - 1D water level calculation


Nowadays the natural design of a watercourse is the main target. This philosophy is based on the idea of an overall water management. In the past rivers were regarded as channels with sewer function. Therefore they were regulated and the vegetation of the flood plain and in the water transition area was removed. These measures caused an increase of flood discharge and as a consequence the water level rose,furthermore the bed load and sediment is scoured during strong floods.

Dealing with ecological water management the natural watercourse should be preserved as naturally as possible. The conservation of the integrated water body in its environment, including biological aspects as well as scenic beauties, is one of the basic principles. This includes the preservation of vegetation and naturally deformed bed load structures in order to preserve a habitat for fauna and flora. These rough elements cause more complex flow processes. In order to display these interactions between vegetation and rough elements in rivers, hydraulic models are used.

Quite a fast method of calculating the flow pattern in open channels is the one dimensional, steady simulation of the water level. This method reduces multidimensional, natural processes to one-dimensional questions by adopting a constant velocity and movement of the water along the flow path.

If the movement of a water body is reduced to a one-dimensional problem, all calculated results will be average values. That means the parameter is averaged over the water depth and the cross section. Only the alteration of the considered parameters, such as the velocity of the water body, along a streamtube is calculated. Of course such a 1D-model is also applicable for channels, embanked watercourses and pipe flow processes. Primarily the hydraulic processes are considered before the basic equations for one-dimensional flow problems are set up.

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