Advancing the Integration of Vegetation in Floodplain Modeling

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cbec collaborated with River Partners and DWR to develop a workshop that explores design concepts and techniques to advance the integration of vegetation in floodplain modeling and management.

Vegetation on floodplains can be designed, modeled, and ultimately managed to achieve engineering and ecological objectives, such as maintaining flood conveyance while accommodating the establishment and growth of riparian plant communities.

cbec prepared model case studies showing how placement of plants can direct overbank flows, improve flood storage, reduce scour and erosion, facilitate sediment transport, and alleviate other flood risk factors, while providing critical habitat. For example, the top figure to the right shows the distribution of hydraulic roughness values associated with a planting “palette” designed to direct overbank flood flows. The bottom figure shows the resulting 2-dimensional model output for the given planting “palette”.

Numerical models can be a powerful tool to help achieve multi-objective benefits in floodplain management; however, the representation of vegetation in models is often rudimentary. Plants play a key role in how processes and functions are expressed and hydraulic roughness is the principle model parameter describing how plants interact with flood water.  Roughness is commonly over-simplified in models leading to missed opportunities for risk reduction and ecological enhancement. Aligning plant characteristics to variations in roughness is a key factor in integrative floodplain design that is promoted by this project.

Details

Watershed: Feather
Project: 13-1020

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