A one-dimensional flood routing model for rockfill dams considering exit height

Abstract

To predict the phreatic surface and conduct flood routing of rockfill dams, the flow hydraulics and rating curve need to be simulated. In this research, one-dimensional flow hydraulics through a trapezoidal rockfill dam was modelled via the standard step method. Regarding the non-Darcy flow, the relationship between the hydraulic gradient and the bulk velocity in power form was adopted. Using the exit height as the boundary condition significantly improves the prediction of the phreatic surface. For this purpose, a modified Pavlovsky equation was introduced. The advantage of the proposed method is that, unlike in previous studies, the downstream water level is used to estimate the exit height instead of the upstream water level, which makes the model more grounded on steady gradually varying flow. The proposed model has the capability of predicting the reservoir head–outflow relationship and routed hydrographs with high accuracy comparable with that of two-dimensional models.