Event Title

Comparing Approaches and Results of Independent 2D Hydraulic Modeling Efforts

Presenter Information

Mike Schubert, HDR Engineering

Streaming Media

Duration

00:23:12

Start Date

8-20-2014 9:15 AM

End Date

8-20-2014 9:40 AM

Abstract

The Iowa Department of Transportation (IaDOT) recently completed a study in which they analyzed the impact of the U.S. Highway 65 (US 65) bypass and embankment had on Des Moines River water surface elevations (WSELs) during recent flood events. The study evaluated pre- and post- bypass conditions as well as mitigation alternatives to reduce impacts caused by the bypass. IaDOT performed the hydraulic study using a two dimensional (2D) hydraulic solver, TUFLOW. The study area encompasses approximately 12 miles. HDR Engineering (HDR) developed a separate, independent 2D hydraulic analysis to confirm the reasonableness of the results. HDR performed their independent hydraulic analysis using the Bureau of Reclamation’s 2D hydraulic solver, SRH-2D.

Resultant water surface elevations (WSELs) were compared at 25 locations in the model. Despite some differences in the resultant WSELs, the two models generally yielded similar results. In areas where results deviate significantly and systematically , corresponding differences in the model setup (for instance, agricultural berm representation and Manning’s roughness coefficient differences) suggested that these differences were not solely numerical in nature, but are likely a result of model inputs and setup.

Simulations to confirm the degree to which differences in computed water surface profiles were reconcilable by adjusting only model inputs and sensitivity simulations were made. The results from these simulations demonstrated that a significant portion of the difference in the predicted WSEL between the TUFLOW and SRH-2D models can be accounted for in model inputs. However, there are still small differences between the predicted WSELs. This comparison sheds light on the degree of variation that can result from using different modeling approaches.

Contact Information

Mr. Mike Schubert

Water Resources Engineer

HDR Engineering, Inc.

300 East Locust Street

Suite 210

Des Moines, IA 50309

Phone: 515-280-4949

email: Michael.Schubert@hdrinc.com

Speaker's Biography

Mike is a Water Resources Engineer working in HDR's Des Moines office. He has completed projects involving watersheds, habitat restoration, rivers, lakes, and streams and has conducted hydraulic analysis on rivers such as the Platte, Snake, Missouri, Mississippi, Iowa and Des Moines Rivers. Mike has performed analysis studies for habitat restoration/enhancement, bridge replacement, flood mitigation and lift station design projects. His background is in water resources engineering and computational hydraulics, and has authored conference proceedings in the area. He is experienced in SRH-2D, HEC-HMS, TUFLOW, FLOW 3D, HEC-RAS, FLUENT, and ADCIRC.

Rights

Copyright © 2014, Mike Schubert

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Aug 20th, 9:15 AM Aug 20th, 9:40 AM

Comparing Approaches and Results of Independent 2D Hydraulic Modeling Efforts

The Iowa Department of Transportation (IaDOT) recently completed a study in which they analyzed the impact of the U.S. Highway 65 (US 65) bypass and embankment had on Des Moines River water surface elevations (WSELs) during recent flood events. The study evaluated pre- and post- bypass conditions as well as mitigation alternatives to reduce impacts caused by the bypass. IaDOT performed the hydraulic study using a two dimensional (2D) hydraulic solver, TUFLOW. The study area encompasses approximately 12 miles. HDR Engineering (HDR) developed a separate, independent 2D hydraulic analysis to confirm the reasonableness of the results. HDR performed their independent hydraulic analysis using the Bureau of Reclamation’s 2D hydraulic solver, SRH-2D.

Resultant water surface elevations (WSELs) were compared at 25 locations in the model. Despite some differences in the resultant WSELs, the two models generally yielded similar results. In areas where results deviate significantly and systematically , corresponding differences in the model setup (for instance, agricultural berm representation and Manning’s roughness coefficient differences) suggested that these differences were not solely numerical in nature, but are likely a result of model inputs and setup.

Simulations to confirm the degree to which differences in computed water surface profiles were reconcilable by adjusting only model inputs and sensitivity simulations were made. The results from these simulations demonstrated that a significant portion of the difference in the predicted WSEL between the TUFLOW and SRH-2D models can be accounted for in model inputs. However, there are still small differences between the predicted WSELs. This comparison sheds light on the degree of variation that can result from using different modeling approaches.