Upstream Thinking: Integrated Hydrologic and Hydraulic Modeling to Improve Upland and Floodplain Restoration Design
Michael T. Coco, PE
WSP USA
Dallas, TX
Authors: Coco, Michael T., PE, Smolko, J., Lennon, Justin M., PE
Using two-dimensional hydraulic models has become commonplace in stream restoration project planning and design. Two-dimensional models enable simulation of distributed velocity and shear stresses throughout project areas to improve stream restoration design. Modeling software like HEC-RAS 2D now allows modelers to simulate precipitation over 2D flow areas with relative ease. Rain-on-Grid simulations offer stream restoration practitioners an opportunity to advance their analysis by investigating upland hydrologic interactions. Mapping overland flow concentration during runoff generation in floodplains and wetlands can optimize upland and floodplain design features.
The Baltimore County Department of Environmental Protection and Sustainability (DEPS) has identified an Unnamed Tributary to Gwynns Falls at Epping Forest Way (Owings Mills, MD) as a priority restoration project. This project involves restoring over 3,500 linear feet of mainstem and tributary channels. DEPS has embraced the use of 2D hydraulic modeling, including Rain-on-Grid simulations, as an innovative approach to data-driven decision-making in upland and floodplain restoration design.
Working closely with DEPS, the design team developed a detailed 2D riverine model of the existing and proposed project area that allowed us to investigate the relationship between high shear stress and channel impairment, and to optimize the proposed channel design to minimize those stresses. We then developed an additional Rain-on-Grid overlay to evaluate ponding and flow paths in overbank areas dominated by small gullies. This technique uses precipitation as a direct input over the 2D flow area and utilizes HEC-RAS as both a hydrologic and hydrodynamic model.
This Rain-on-Grid analysis allowed the design team to consider existing drainage patterns and evaluate a series of proposed upland modifications to better convey overland flow patterns compared to existing conditions. This presentation will show how this accessible approach can be a useful indicator for flood storage and overbank hydraulic routing through complex topography.
About Michael T. Coco, PE
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