Dam Breach Modeling and Inundation Mapping

Several software packages for simulation of the propagation of flood waves generated by breaching dams and for inundation mapping are used for dam safety purposes. The National Weather Service modeling systems DAMBRK and FLDWAV are being widely used. Most recently dam breach simulation capabilities have been added to HEC-RAS. Floodplain modeling efforts have moved to include unsteady-flow one-dimensional (1 D) models, and lately to also include steady and unsteady two-dimensional (2D) models, and even dynamically coupled 1 D / 2D models. The use of multi-dimensional models has also been spurred on by the increasing availability of LIDAR topography, which allows for the modeler to describe large areas of floodplain with greatly increased accuracy and greatly reduced survey costs. This is a major advance in terms of describing broad floodplains, as a more detailed modeling effort is meaningless in the absence of equally detailed input data. In the western U.S., the Bureau of Reclamation has applied a combined 1D and 2D modeling approach for the purpose of evaluating flood inundations of dam and levee failures at a variety of sites having complex geometries. Integrated one and two dimensional modeling systems such as MIKE 11 and MIKE 21, providing similar modeling capabilities, a user-friendly graphical user interface and GIS flood mapping features, have in the recent years become widely used for integrated simulation of reservoir inflow forecasting, dam failure, flood wave routing, inundation modeling and GIS mapping. The paper presents an inter-comparison of MIKE 11, DAMBRK and FLDWAV including comparison of modeling capabilities and techniques on a theoretical level as well as comparison of simulation results from a number of real applications. Finally the combined one/two dimensional modeling approach and user interface and additional features such as flood mapping capabilities Will be presented and compared. 16 pp., 11 figures, 6 references.