Comparison of One-Dimensional and Two-Dimensional Hydrodynamic Modeling Approaches For Red River Basin

A devastating flood in Red River valley in 1997 emphasized the need to study the flood control measures in the Red River basin using state of the art modeling tools. The Red River and its floodplains can be modeled using one-dimensional, quasi two-dimensional or fully two-dimensional hydrodynamic models. Each modeling approach has its own advantages and limitations. The main purpose of this report is a comparison between one-dimensional (or quasi two dimensional) and fully two-dimensional hydrodynamic modeling approaches for modeling floods in the Red River basin. A two-dimensional hydrodynamic model, MIKE 21, coupled with Geographic Information System (GIS) has been used in this study to capture the hydraulic response of the Red River and its floodplains in extreme flooding conditions. The focus area for modeling is a section of the Red River basin from south of Winnipeg floodway to the town of Ste. Agathe in Manitoba, Canada. For comparison purposes, results produced by Klohn-Crippen (1999), using one-dimensional unsteady flow model, MIKE 11, have been used. MIKE 21, two-dimensional unsteady-flow model, is based on the finite-difference solution scheme and uses rectangular grids to resolve bathymetry. Simulations are made, using MIKE 21, to study the impact on flooding by modifying the operation of floodway. Problems associated with the application of a 2-D model are discussed especially with respect to the representation of terrain.-4-Based on comparison of results, produced in this study using two-dimensional model MIKE 21 and reported by Klohn-Crippen (1999) using one-dimensional model MIKE 11, it is recommended that: 1. The whole Red River basin should be modeled using a combination of quasi two-dimensional and fully two-dimensional models. 2. Fully two-dimensional model should be used only for areas of interest where detailed description of flow field is required, for example in the vicinity of major structures, communities and sensitive areas with high flood damage potential. Using combined modeling approach boundary conditions for two-dimensional model can be derived from results produced by one-dimensional model.-5