Application of numerical models for improvement of flood preparedness

Modeling the movement of flood waters can be accomplished using many different methods with varying degrees of physical detail. Numerical models utilizing simple routing methods or simplified versions of the Navier-Stokes equations can be used to improve the public's flood preparedness. Three numerical models are used in this thesis to investigate flood preparedness: (1) an existing HEC-ResSim model of Coralville Reservoir, (2) an existing one-dimensional HEC-RAS model of the Iowa River through Coralville and Iowa City, and (3) a coupled one/two-dimensional hydraulic MIKE Flood model of the Cedar River through Cedar Falls/Waterloo. The HEC-ResSim model of Coralville Reservoir, provided by the United States Army Corps of Engineers, requires reservoir elevation-storage curves, inflow hydrographs and user-defined operation rules. This model utilizes level pool routing to determine changes in reservoir water levels and attenuation of hydrographs. The Muskingum routing method is used to route controlled releases downstream and determine satisfaction of constraints. The model is used to determine the impact of operational changes and sedimentation effects on historic flood events. Simulations indicate sedimentation has no effect on peak discharges of extreme events, but more aggressive operations plans may provide additional storage prior to extreme events. The existing HEC-RAS of the Iowa River through Iowa City is used to develop a library of inundation maps to be hosted on the National Weather Service Advanced Hydrologic Prediction Service's river forecast website. The modeling method assumes steady gradually varied flow. Post-processing and visualization of simulation results are completed using a digital elevation map of the study area developed using topography, bathymetry, and structural elevations. A coupled one/two-dimensional MIKE Flood model is developed for the Cedar River through Cedar Falls/Waterloo using topography, bathymetry, land use, and structural data. The river channel is modeled using MIKE 11, a one-dimensional unsteady hydraulic model, while the flood plain is modeled using MIKE 21, a two-dimensional hydraulic model utilizing depth-averaged Navier-Stokes equations. The model is used to develop a sequential levee closure plan for downtown Waterloo and will also be used to develop a library of inundation maps.