Event Title

Predicting storm impacts on gravel beaches in Puget Sound using the XBeach-G model

Presentation Abstract

One of the significant challenges of removing shoreline armor along Puget Sound beaches is availability of prediction tools to determine quantitatively how the gravel beach will react to storm wave conditions once the armor is removed. Appropriate sites for armor removal or feasibility of soft shoreline stabilization are typically chosen based on screening parameters (i.e. fetch distance) that identify sites as having low erosion potential. While these screening tools are adequate for identifying potential sites, additional analyses are required before moving forward with armor removal or to complete a soft shoreline design. Many existing analytical methods and models that predict or simulate beach changes due to storm waves were developed and validated for sand beaches. Puget Sound beaches primarily consist of gravel or mixed gravel-sand substrate. The hydrodynamic processes for mobilizing and transporting gravel in the surf and swash zones is quite different than the process for sand; therefore, many existing methods and models are not appropriate for use in Puget Sound. Deltares, in collaboration with Plymouth University, has developed a model called XBeach-G specifically to simulate storm impacts on gravel beaches. We will be presenting a series of case studies conducted to evaluate the performance of the XBeach-G model in predicting morphology change of gravel beaches in Puget Sound. Case studies sites were chosen based on availability of longer term nearshore topography data at the site. Model simulations of morphology change of the gravel beaches at each site were compared to empirical site data. In addition, a sensitivity evaluation was conducted to determine impacts on model results from reasonably small changes to model input information. Preliminary results suggest that the XBeach-G model is a viable tool for predicting future morphology change of gravel beaches in Puget Sound following armor removal or performance of gravel beach nourishment projects.

Session Title

Posters: Habitat Restoration & Protection

Conference Track

SSE18: Posters

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE18-135

Start Date

5-4-2018 11:30 AM

End Date

5-4-2018 1:30 PM

Type of Presentation

Poster

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

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Apr 5th, 11:30 AM Apr 5th, 1:30 PM

Predicting storm impacts on gravel beaches in Puget Sound using the XBeach-G model

One of the significant challenges of removing shoreline armor along Puget Sound beaches is availability of prediction tools to determine quantitatively how the gravel beach will react to storm wave conditions once the armor is removed. Appropriate sites for armor removal or feasibility of soft shoreline stabilization are typically chosen based on screening parameters (i.e. fetch distance) that identify sites as having low erosion potential. While these screening tools are adequate for identifying potential sites, additional analyses are required before moving forward with armor removal or to complete a soft shoreline design. Many existing analytical methods and models that predict or simulate beach changes due to storm waves were developed and validated for sand beaches. Puget Sound beaches primarily consist of gravel or mixed gravel-sand substrate. The hydrodynamic processes for mobilizing and transporting gravel in the surf and swash zones is quite different than the process for sand; therefore, many existing methods and models are not appropriate for use in Puget Sound. Deltares, in collaboration with Plymouth University, has developed a model called XBeach-G specifically to simulate storm impacts on gravel beaches. We will be presenting a series of case studies conducted to evaluate the performance of the XBeach-G model in predicting morphology change of gravel beaches in Puget Sound. Case studies sites were chosen based on availability of longer term nearshore topography data at the site. Model simulations of morphology change of the gravel beaches at each site were compared to empirical site data. In addition, a sensitivity evaluation was conducted to determine impacts on model results from reasonably small changes to model input information. Preliminary results suggest that the XBeach-G model is a viable tool for predicting future morphology change of gravel beaches in Puget Sound following armor removal or performance of gravel beach nourishment projects.