The effects of hydraulic resistance in the dam-break problem

When resistance is neglected, the solution of the simple dam-break problem is readily obtained on the basis of shallow-water theory, and the results are well known. However, near the head of the wave, where the water surface meets the ground, resistance effects cannot be neglected; there is, in fact, a type of boundary layer near the wave-front. In this paper, the Pohlhausen method (which is used in conventional boundary-layer problems) is applied to a study of the effect of this ‘boundary layer’. In particular, the retardation of the wave-front behind the position predicted by the simple theory is found.