River Modeling as a Tool for Public Flood Preparedness
Iowa City during the 2008 flood (UI News Services).
Project Personnel (University of Iowa): Dr. Nathan Young (Research Engineer), Radoslaw Goska (Engineer II), Andrew Craig (Engineer II), Jesse Piotrowski (Graduate Student), Bo Chen (Graduate Student), Daniel Gilles (Graduate Student), Kyutae Lee (Graduate Student), Matt Moore (Undergraduate Student), and Alex Bouge (Undergraduate Student).
Experiences from the 2008 flood demonstrated that many communities and residents were not able to interpret and utilize much of the available forecast information in coordinating flood fighting efforts. This project is an effort to develop libraries of flood inundation maps associated with different river flow conditions to more effectively communicate flood data to the general public. Final inundation maps will be publically available via Google Earth and other web-based applications. This information will allow public officials, residents, and business owners to visualize how predicted flow rates or river stages may potentially affect their communities and properties, and to take appropriate action to ensure safety and minimize flood damage.
Study Locations
Location of Current Flood Inundation Mapping Projects
We are developing and testing methods using a 10-mile stretch of the Iowa River, beginning immediately downstream of the Coralville Reservoir extending downstream through Iowa City. Based upon lessons learned in the Iowa City/Coralville area, we are creating similar maps for communities throughout the state. We are focusing our initial efforts on the communities of Cedar Falls, Waterloo, and Charles City, and in numerous small communities to the south of Iowa City (see map).
Steps in the Development of Inundation Maps
Methods
A computer model of each river reach is required to create inundation maps corresponding to various flow conditions. First, the geometry of the land surface (topography) and river bed (bathymetry) must be measured. Topography is measured using airplane-based stereoscopic imaging and light detection and ranging (LiDAR) technologies. Bathymetry is measured using advanced sound navigation and ranging (SONAR). Topography and bathymetry are combined to create a continuous, high-resolution digital elevation model (DEM). Additionally, data describing the geometry of buildings in the floodplain, bridge piers, culverts, and low-head dams, and data describing land use and cover must be attained.
A numerical model is then generated from the DEM and geometric data. The flow rates of water entering the model are determined from U.S. Geological Survey (USGS) river gages. There are various parameters that determine where water will flow in the model. To ensure that these parameters are correct, the model must be calibrated to measured water surface elevations (for a given flow rate) at numerous locations. To validate the model (confirm the model is properly calibrated) its performance is compared with an additional, independent set of measured water surface elevations. The calibrated, validated model can then be used to predict the flooding extent of the river under different conditions. Thus inundation maps for virtually any possible flow rate can be created.
Funding Sources for this Project:
