Backwater Computation for Choking Flood Flows through Bridge Contractions

Abstract

A new method for the computation of backwater profiles for choking flows due to bridge contractions is proposed. This method was derived from energy, momentum, and water continuity equations. The computations considered the critical flow condition at the contraction, which forms the control section for the upstream flow of the contracted reach. In addition, the energy losses associated with the local contraction were also taken into account. The proposed method was tested by applying it to a large flood which occurred at an Interstate 5 (1-5) bridge over Los Gatos Creek near Coalinga, California in 1995. Results indicate that the proposed method can be used to compute the backwater profile for choking flows in practical applications.