Flood Wave Modeling Based on a Two-Dimensional Modified Wave Propagation Algorithm Coupled to a Full-Pipe Network Solver

Abstract

Flood propagation over urban areas can cause an interaction between the free-surface flow and large underground pipe networks used for sewage and storm drainage, causing outflows and inflows at the bed. The waves resulting from these bed discharges may collide with each other and the surface waves, increasing water depths, velocities and accelerations, and their interaction thus affects flood risk. The authors previously introduced a one-dimensional (1D) shallow-water model for simulating free-surface interaction with the flows issuing vertically through finite gaps, referred to as efflux. This model used a modified wave propagation algorithm and was validated by comparing results with the full Navier-Stokes equation solver (STAR-CD) based on the volume-of-fluid method, which models free-surface motion quite generally, although at considerable computational expense. The present paper extends the shallow-water scheme to two dimensions, including source terms for pipe outflow/inflow (efflux/influx) and bed friction and bathymetry gradients. A general pipe network solver for full flow is coupled with the free-surface flow. The methodology is first tested with idealized cases. Two-dimensional (2D) dam-break flow over a complex bed profile without efflux/influx at the bed is first modeled. Next, efflux discharge is modeled in isolation over a dry bed and then with dam-break interaction, comparing with 3D STAR-CD results. Results for these idealized cases are in good agreement. Finally dam-break interaction with a pipe network of 25 nodes demonstrates the complex bore interaction.