Presentation Abstract

Large Woody Debris (LWD) accumulates naturally in the coastal environment (Brennan et al., 2009; Sass, 2009) and is thought to be a vital component of a diverse coastal habitat ( Rich et al., 2014). Decreasing natural coverage of LWD (Heathfield & Walker, 2011) and increasing demand for environmentally sensitive coastal protection techniques has led to the promotion of LWD as a viable nature-based method of shoreline protection (e.g. Johannessen et al., 2014; Stewardship Centre for BC, 2016; Washington Department of Fish and Wildlife, 2016). However, there is currently no peer-reviewed literature assessing the efficacy of coastal protection using LWD. This presentation will summarize the results of field investigations focused on assessing the legacy of existing coastal protection or restoration projects using LWD in BC and Washington. Over 30 project sites were identified as having used LWD as a component of the project, generally with the aim of reducing wave induced flooding and/or shoreline erosion. Between June – August 2019, field investigations were conducted at 15 of these existing installations in BC and Washington. The projects ranged in installation date (1999-2018), extent (small private-properties to extensive parks), and design (groynes to large matrix-style installations). Measurements of the LWD placement elevation and beach slope were made using an RTK GPS within BC, and a rotary laser level and rod within Washington where site-access permitted. Surficial sediment sizes were estimated using digital grain size analysis. Additional observations were made on log size, anchoring technique, signs of beach erosion/accretion, and signs of damage to the LWD or anchoring system. This presentation will provide background on the monitoring techniques utilized, summarize key findings of the field investigation, provide preliminary design guidance for the use of LWD as coastal protection, and highlight the value of monitoring and re-evaluating legacy projects.

Session Title

Session 2.3A: Measuring Success: Monitoring the Effectiveness of Shoreline Restoration Projects

Conference Track

Shorelines, Estuaries & Rivers

Conference Name

Salish Sea Ecosystem Conference (2020 : Online)

Document Type

Event

SSEC Identifier

2020_abstractID_2582

Start Date

22-4-2020 2:30 PM

End Date

22-4-2020 3:30 PM

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

Language

English

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Apr 22nd, 2:30 PM Apr 22nd, 3:30 PM

Assessing the Legacy of Large Woody Debris as Coastal Protection in BC and Washington

Large Woody Debris (LWD) accumulates naturally in the coastal environment (Brennan et al., 2009; Sass, 2009) and is thought to be a vital component of a diverse coastal habitat ( Rich et al., 2014). Decreasing natural coverage of LWD (Heathfield & Walker, 2011) and increasing demand for environmentally sensitive coastal protection techniques has led to the promotion of LWD as a viable nature-based method of shoreline protection (e.g. Johannessen et al., 2014; Stewardship Centre for BC, 2016; Washington Department of Fish and Wildlife, 2016). However, there is currently no peer-reviewed literature assessing the efficacy of coastal protection using LWD. This presentation will summarize the results of field investigations focused on assessing the legacy of existing coastal protection or restoration projects using LWD in BC and Washington. Over 30 project sites were identified as having used LWD as a component of the project, generally with the aim of reducing wave induced flooding and/or shoreline erosion. Between June – August 2019, field investigations were conducted at 15 of these existing installations in BC and Washington. The projects ranged in installation date (1999-2018), extent (small private-properties to extensive parks), and design (groynes to large matrix-style installations). Measurements of the LWD placement elevation and beach slope were made using an RTK GPS within BC, and a rotary laser level and rod within Washington where site-access permitted. Surficial sediment sizes were estimated using digital grain size analysis. Additional observations were made on log size, anchoring technique, signs of beach erosion/accretion, and signs of damage to the LWD or anchoring system. This presentation will provide background on the monitoring techniques utilized, summarize key findings of the field investigation, provide preliminary design guidance for the use of LWD as coastal protection, and highlight the value of monitoring and re-evaluating legacy projects.