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Applications of 2D Hydraulic Modelling to Ecosystem Restoration

Robert Stewart, PhD, PE
Water and Land Solutions
Johnson City, TN

The ecosystem restoration community frequently employes 2D hydraulic models during project planning, design, and permitting. This presentation uses 3 projects to illustrate various objectives and presentations of 2D hydraulic model outputs. The presentation provides a brief statement of objectives for each project and shows:

1.  The first project is on a large (>1000 mi2) gravel bed river mountain river located in northern California with a mean annual precipitation of 52.6 inches. Velocity and depth regimes were combined with habitat suitability for juvenile Coho salmon to estimate pre- and post-construction habitat availability. Flow dependent habitat availability increased for all flow simulations with the greatest increase in habitat occurred when flows overtop the banks.

2.  The second project is a small (≈2 mi2) headwater urban stream daylighting project located in Pittsburgh PA. Visualizations produced of flow depth estimated from a 2D hydraulic model was combined with 3D surface topography and areal imagery to provide the public and stakeholders illustrations of future conditions. The 2D model simulates an unsteady hydrograph of the proposed project to demonstrate peak flow attenuation to help communicate flood reduction potential to the project sponsor.

3.  The third project involves dam removal and pond conversion on a small headwater system to a wetland stream complex in northern West Virginia. A series of 4 ponds were removed and a single thread channel was created through a complex of wetlands. A 2D hydraulic model on the existing conditions highlighted risk and potential flooding issues associated with dam overtopping. These modelling efforts provide impatience to convert the ponds to a natural stream corridor.

During the planning, design, and permitting phases of these three projects 2D hydraulic models played an invaluable role in demonstrating project effectiveness in a manner that is easily communicated. Hydraulic models are an effective communication tool when project objectives are well understood.