The Bell-Shaped Unit Hydrograph for Overland Planes

Abstract

This study presents a conceptual model to obtain the shape of the unit hydrograph in a small rectangular basin with a collecting channel on one side of the flow plane. In classical hydrology, flows are classified as linear, convergent, and divergent. In the proposed model, a rainfall of constant intensity is assumed, with the duration equal to the time of concentration of the basin, as in the rational method. The shape of the plane is simplified in order to obtain an analytical solution. It is observed that in the plane of diffuse flow, the flow begins as a convergent of repletion, then passes to divergent of repletion, and finishes as a convergent of depletion. The applied theory allows the development of a classic bell-shaped unit hydrograph, a very common form of the theoretical hydrographs found in the literature. The proposed methodology was also applied to a practical flood damping problem in an urban watershed.