Does Mesh Resolution Matter? The Importance in 2D Modeling

Often the mesh resolution used in a 2D model comes down to reasonable run times, but what impact does that have on the analysis and ultimately the results? In this presentation we'll take a look at the results of a fully 2D hydraulic model with varying levels of mesh resolution and see how calibration was also impacted. In 2008, Iowa City, IA experienced a catastrophic flood event. Soon after the event, 23 high water marks were collected throughout the city for the purpose of building and calibrating a hydraulic model. Along with as-built plans for the bridges, land use, and DEM, a fully 2D hydraulic model was built and calibrated. Four copies of the model were made in order to build different models with varying levels of detail and ranged from having ~1.5 million cell elements to ~75k cell elements. Results from each model were compared to each other at each of the high water marks to highlight differences and statistical error between each one. Additionally, the four copies were then re-calibrated to try to reduce the amount of difference and error which ultimately resulted unrealistic modeling parameters. As 2D hydraulic modeling becomes more prevalent in the stormwater industry, its important to understand how some of the fundamental and initial decisions when beginning a 2D hydraulic analysis will impact the results. This presentation is designed to highlight why mesh resolution is such an important decision and should be given a higher level of attention beyond just a consideration for run times.