Simulation of Midwest Flood 2008: Levee Breaching and Flood Propagation

摘要

In June, 2008, the Mississippi River in the Midwest USA experienced a high flood. More than 22 breached levees were observed along the Mississippi River, resulting in at least 24 fatalities in 51 counties in 5 states (Illinois, Missouri, Wisconsin, Iowa, and Minnesota). In order to study the flood impact on agriculture in the flood zones, the computational model, CCHE2D, was applied to simulate levee breaching and flood propagation in one reach of the Mississippi River near Canton City, Missouri. Due to the difficulty in obtaining field data for such large scale problems, remote sensing imageries were used to estimate the location, width and timing of breaching, the distribution of Manning's resistance coefficients, and the inundation area. The computational model was verified and validated using mathematical methods, as well as experimental and field dam break flow data before being applied to this case. A series of satellite imagery and several digital image processing techniques were used to identify the processes of flood wave propagation and inundation in the field for this study. Because levee breaching took a short time in comparison to that of the overall flooding process, the levee breaching process was computed using a simplified model to enhance computing efficiency. A hybrid method to combine the explicit and implicit scheme-based models was also developed and applied which greatly reduced the simulation time. The total time needed with this hybrid method was about 2% of that for the explicit method. The computational results have been compared with a series of satellite digital imagery, and it shows the simulation agreed well with what happened. The developed modeling system has a strong potential to be used for emergency management.