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.