Two-Dimensional SRH-2D Modeling to Identify and Evaluate Habitat Enhancement and Flood Hazard Reduction Actions on a Reach of the Yakima River
Abstract
Integrated floodplain management requires balancing competing needs along a river reach. This includes the desire to make room for fish through in-stream restoration and other habitat enhancement projects, as may be required to mitigate for transportation projects, as well as preservation of floodplain function by setting back or removing levees altogether. On the other hand, existing floodplain development, transportation infrastructure and agricultural use require some level of flood and bank protection or mitigation to ensure safety and viability. Finding reliable solutions to complex multi-objective problems such as this requires thoughtful and sophisticated analyses.
Two-dimensional numerical hydraulic modeling provides a useful tool for accurately establishing existing conditions from which to test and identify possible strategies for integrated floodplain management. The model can be used to evaluate multiple alternatives for both channel restoration and flood protection, to help identify which actions or combinations thereof are most effective without causing unacceptable impacts. Results of two-dimensional modeling are well-suited for presenting to non-technical stakeholders, including landowners, to help them easily understand the benefits and impacts of proposed alternatives.
As part of the Yakima River Basin Water Enhancement Project, the U.S. Bureau of Reclamation (USBR) has been examining the rehabilitation potential for a reach of the Yakima River along Interstate 90 near Ellensburg, Washington. Likewise, Watershed Science and Engineering (WSE) is working with Kittitas County to develop a master plan to guide the enhancement of salmonid habitat and reduce flood hazards along the immediate downstream reach of the Yakima River which is comprised of mixed rural and suburban floodplain development, agricultural lands, park and open space, and abandoned DOT gravel pits. Two-dimensional modeling has been undertaken for both projects to help identify and develop effective alternatives for improving aquatic habitat as well as providing reasonable flood and erosion protection. The SRH-2D modeling program, using the SMS software, is being used to simulate conditions along a total of 5 miles of the river above the Yakima River Canyon. The model provides a defensible tool for evaluating project alternatives and facilitates production of simple and understandable graphics to inform and engage the stakeholders, whose participation is an essential component to the process.
The presentation will review the two-dimensional model and its original development by the USBR and subsequent downstream extension by WSE, and then discuss how it has been used to map and verify existing habitat and flood and erosion hazards. Use of the SRH-2D model to identify proposed actions for reducing flood and erosion hazards as well as enhancing habitat will be demonstrated. Alternative actions being considered include setback levees and preserving and/or creating side-channel habitat, among other strategies. Features and capabilities of the SRH-2D modeling program will be highlighted, including its benefit not only for this project but also for other integrated floodplain management or transportation development and mitigation projects.
How to Cite:
Elliot, R. & Sabatine, S. & Hilldale, R., (2014) “Two-Dimensional SRH-2D Modeling to Identify and Evaluate Habitat Enhancement and Flood Hazard Reduction Actions on a Reach of the Yakima River”, National Hydraulic Engineering Conference 2014 1(2014).
Rights: Copyright © 2014, Bob Elliot, Shaina Sabatine, and Rob Hilldale
Publisher Notes
- Panel moderated by Wesley Peck, TDOT.
- About the Presenters: Bob Elliot is a Senior Hydraulic Engineer with Watershed Science & Engineering in Seattle, Washington. He has more 25 years of experience as a hydraulic engineer, specializing in the application of advanced numerical modeling to better understand and solve challenging problems in rivers and floodplains. He leads WSE’s numerical modeling program, and is familiar with a wide range of modeling software, including various one-dimensional programs such as HEC-RAS steady and unsteady, WSPRO, MIKE 11, and FEQ, as well as multi-dimensional programs typically using the SMS pre- and post-processing software. These include FST2DH (FESWMS), RMA2, RiverFLO-2D, and most recently SRH-2D. Specific modeling assignments related to transportation issues have included bridge design and replacement projects, scour evaluations, simulation of alternatives to mitigate transportation impacts, flood control to protect transportation infrastructure, and evaluation of embankment erosion and countermeasures. Many recent projects have involved multiple stakeholders with different objectives, and seek to find a balanced solution with regard to the needs for flood control, channel stability, habitat restoration, transportation, agriculture and other land uses. He will speak today about one such project, and the use of SRH-2D modeling to map hazard areas and identify alternative solutions.
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