Two‐Dimensional Flood Routing on Steep Slopes

Abstract

Program ROUTWEIR represents a two‐dimensional flood routing model designed to analyze two‐dimensional flow caused by rainfall and runoff flooding events. Input to the program consists of known geometry, topography, initial conditions, and boundary conditions. The geometry and bathymetry of the flood plain are represented by a grid of interconnecting triangular elements. Initial water levels are prescribed to correspond to the normal water elevations in the river channel. Boundary conditions are prescribed by a discharge hydrograph at the upstream boundary of the river basin, and by the water surface elevations at the ocean boundary. The interior water elevations and discharges are computed, allowing flooding and drying to take place in the triangular elements of the grid, based on a conservation of water volume equation and a surface slope dependent dynamic equation. Output consists of time histories of water surface elevations and peak elevations in both tabular and graphical form. ROUTWEIR has been successfully calibrated against recorded flood levels in the Rio Culebrinas Basin in Puerto Rico and has been used in that basin in a federal flood insurance study. A versatile computer program, ROUTWEIR can be applied to many flood routing problems. It is particularly suited for wide river basins with large bottom slopes and for normally dry areas subject to extensive flooding.