UMRS Hydraulic Model Update - Questions & Answers

The Corps of Engineers has recently completed new, updated hydraulic models for the Upper Mississippi River System, including the Illinois Waterway. This collaborative effort involved review and coordination with a variety of state and federal agencies, and was facilitated by the Corps of Engineers Rock Island, St. Louis and St. Paul Districts, and uses the Hydrologic Engineering Center's River Analysis System (HEC-RAS).

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 Who will be able to run the model? Will it require a model developer to conduct model runs or will the model include a user-friendly interface so it can be run by scientists or managers in workshops?

An experienced HEC-RAS hydraulic modeler will be able to run the model. It is important to have an experienced hydraulic modeler to assure appropriate use of the model inputs and modeling results. Most likely a scientist or manager would not have the training or experience to make modeling run in a workshop setting.

 How were model parameters determined?

The updated HEC-RAS model parameters were reviewed and determined by the technical team using standard modeling practices, professional judgment, and by calibration of the model to observed data.

 Who will have access to an electronic copy of the model?

An electronic copy of the updated HEC-RAS model will be available to anyone wishing to obtain a copy.

 Will the Corps be continuously updating the model to account for changes in the river system, both flow and physical changes in the river? What mechanism triggers model review?

Federal and state users of the model will periodically evaluate when the HEC-RAS model needs updating. The need for a model update would be identified by significant changes in system hydrology or topographic features.

 How do you plan on modeling a floodway considering the different state’s floodplain regulations?

The updated HEC-RAS model could provide the basis for future floodway computation, collaboration, and coordination, if desired.  A source of funding would need to be identified for such an effort.

 Were all submerged structures (i.e. wing dams, chevrons, etc.)  included in the model?

HEC-RAS does not attempt to model the near-field, multi-dimensional effects of river training structures. The model incorporates the observed river geometry and bathometric data which reflects the impacts of these structures on the river morphology.

 Is there a process for continuous updates to the base model to fix problems and/or errors that are discovered after the model is released?

Updates required to support water management will be made through the Corps’ future Operation and Maintenance funding, if available. Other modifications to the model will require project funds related to the purpose of the changes.

 Where can the public find the software used to run the model?

The completed model will use HEC-RAS software which is available to the public at the following site:

 Will there be a process to update the "final" model if community identifies data that is inaccurate? What Quality Assurance/Quality Control (QA/QC) was used to in the model development?

If a community determines there may be an issue with the final model, the community should document the issue and contact the Corps to resolve it. During the HEC-RAS model implementation, a QA/QC and a technical review was performed by Corps modeling experts. State and federal agencies were also provided an opportunity to review the model and suggest edits during its development.

 How did the Corps perform outreach to ensure the most up to date survey data was used in the model development?

During implementation, outreach for updated bridge and levee elevation data was requested from federal, state and local partners. Only data certified by a licensed land surveyor was included in the updated model and incorporated where appropriate.

 Were capabilities such as where water goes within the floodplain as discharge rises, water velocities, water depths, and how long water remains in depressions, floodplain lakes, and behind levees as floodwater recedes included in the new model and was desired model outputs regarding inundation including number of days inundated (and continuously inundated), current velocity, and depth of inundation included?

The updated HEC-RAS model can provide a variety of outputs related to ecological and economic analyses. Consultation with a trained and experienced hydrologic modeler should be conducted to determine whether the updated model is appropriate for the required analyses.

 Will the new system-wide model be able to be downscaled to address issues at different spatial scales such as a reach, pool, section of a pool, or the scale of a single habitat rehabilitation project?

The updated HEC-RAS model can be broken down to pool reaches; however, the modeler would need to use the appropriate upstream and downstream boundary conditions for that specific pool reach. Additional downscaling may require the use of other modeling programs. Consult a trained and experienced hydraulic modeler to determine these requirements.

 Will modifications to model geometry, model inputs, or dam control be possible in the new model? If so, could the user make these modifications, or will a model developer need to make them?

Alternatives can be modeled by modifying the updated HEC-RAS model. The alternative would need to be incorporated into a copy of the base condition (i.e., existing condition model) by a hydraulic modeler that has HEC-RAS modeling training and experience.

 Did the model include sediment transport (suspended and/or bed load), or will it in the future?

The updated HEC-RAS model will provide a base-condition hydraulic model that could be modified for various hydraulic modeling applications (i.e. sediment, water quality, etc.) by an experienced HEC-RAS hydraulic modeler with the appropriate HEC-RAS modeling training.

 How were the model assumptions, development, and computational results reviewed?

The updated HEC-RAS model was a coordinated effort involving the Corps of Engineers, Federal Emergency Management Agency, National Weather Service, U.S. Geological Survey; the states of Illinois, Iowa, Minnesota, Missouri, and Wisconsin; and interested private individuals as members of the public involvement group. In addition, technical advisory groups consisting of nationally renowned experts were formed to help address the complex issues of hydrology and hydraulics. The model update process also included comprehensive quality assurance, quality control, and independent technical reviews though several iterations and levels of review.