Maximizing Benefits of Shoreline Armor Removal

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Cramer Fish Sciences is working to develop a study to evaluate the success of shoreline armor removal projects in Puget Sound at increasing juvenile salmon and forage fish abundance and improving habitat conditions. This project will be executed in two phases, Phase I will include the study design, site selection, and pilot execution and will be completed in spring 2024. Phase II, if funded, will include the execution of the armor removal study designed in Phase I. The study will provide timely information to guide the design of future shoreline restoration projects and inform future evaluation efforts.

Crews beach seining at Priest Point, near the mouth of Ebey Slough distributary of the Snohomish River, Photo Credit: Jason Hall

Background[edit]

Shoreline armoring has been identified as a limiting factor for juvenile salmonids, nearshore vegetation, and forage fish (Thom et al. 1994; Cereghino et al. 2012). Shoreline armoring studies are important to identify key restoration actions and prioritize restoration to maximize fish and tidal habitat benefits. More than 60 armor removal projects have been implemented across Puget Sound with limited information on the intertidal fish response. Previous studies have largely been limited to few sites and few have been widespread across the Puget Sound but have developed methodologies for surveying and evaluating habitat, topography, and fish response to restoration. This study will leverage existing studies and available remote sensing data to design a framework for site selection and prioritization, to develop a field protocol for evaluating restoration response to shoreline armoring removal, and to execute the protocol on pilot sites to collect and evaluate new data.

Goals, and Objectives

  • Evaluate the effectiveness of shoreline armor removal at improving local fish use and habitat
  • Determine which projects and/or project types have greater direct benefits for fish and fish habitat
  • Produce concise and practical guidelines for the prioritization, design, and monitoring of future shoreline armor removal projects to maximize fish benefits
  • Generate a quality peer-reviewed manuscript to provide evidence of the potential for beach restoration to provide direct benefits to fish


Key Questions[edit]

  • Have shoreline armor removal projects in Puget Sound improved habitat for juvenile salmonids?
  • Are densities of juvenile salmon higher in treatment (shoreline armoring removal) vs. control areas (armored shoreline)?
  • What are the attributes of projects with the largest benefits to fish?
  • What is the influence of project size, age, treatments, location, and other factors on project benefits?


Phase I Deliverables[edit]

The experimental design will be based on an extensive post-treatment (EPT) design with paired treatment (restored = armor removed) and control (unrestored = armored) sites (Hicks et al. 1991; Roni et al. 2005, 2013). The EPT design has been widely used to evaluate the effectiveness of restoration techniques in both nearshore and riverine environments in Puget Sound, North America, and Europe (Roni et al. 2018). Obtaining unbiased and representative samples requires judicious selection and pairing of treatment and controls to correct for differences among sites. Using this design requires two key components: (1) a large population of restored sites of various ages and treatments to choose from and (2) adequate control sites where shoreline armoring has not been removed with similar physical characteristics (e.g., drift cell, landform, armor type, land use/cover conditions) to the restored site prior to restoration.

Data Compilation
We will compile data from regional sources as well as make direct data requests to Lead Entities and regional managers to create a centralized data inventory of project and region-scale spatial, tabular, and report data related to the Puget Sound shoreline function, condition, and processes. These data will help us to evaluate previous restoration methods and extents and completed and on-going monitoring programs as well as to identify data gaps that could hinder evaluation of projects across the region. A full data inventory will be made available as part of our deliverables.

Site Selection
After reviewing regional data on the suite of restoration sites and identifying key criteria, we will develop and execute a framework for selecting and prioritizing shoreline armoring restoration sites to monitor. We will consider the physical conditions and geographic setting (e.g., drift cell, landform, shore type, land use/cover conditions, fetch, slope), fish use and population dynamics (e.g., presence of spawning activity, proximity to natal populations) restoration methods used, and data available in our site selection. We will also select sites based on the availability of a suitable control to survey, which matches the treatment in pre-project physical and habitat conditions but has not been restored and remains armored.
There are more than 60 potential shoreline armor removal sites in Puget Sound (Roni et al. 2019) and extensive classification of nearshore environment and beaches facilitates pairing of potential control sites (CGS 2017, PSEMP 2021). Moreover, previous studies examining invertebrates, beach wrack, and other physical characteristics have identified and sampled more than 30 potential sites (Morley et al. 2012; Heerhartz et al. 2015; Francis et al. 2020). In addition, the PSEMP Nearshore Workgroup, PRISM database, Soft Shore and Armor Alternative Projects, Shoreline Monitoring, and ESRP Beach Strategies databases provide detailed information on location of potential sites, and previous or ongoing monitoring efforts.

Data Collection
Using existing studies, we will identify key metrics and methods used in the Puget Sound to evaluate shoreline armoring and restoration. Habitat assessment and mapping methods will consider traditional physical monitoring approaches (e.g., wood, sediment, and riparian field surveys) as well as drone-based aerial LiDAR and high-resolution photography to map sites and characterize topography, wood, substrate, and riparian and aquatic vegetation. Data analysis methods will be determined based on the target response metrics and experimental design.
Fish densities are often influenced by strong spatial and temporal variability. Migration pulses, patchiness in distribution, and timing of movement have the potential to influence observations and comparisons among sites (Rice et al. 2011; Hayes et al. 2019). Our study design will address this by sampling paired sites during the same sampling events and comparing differences between paired sites using both abundance and presence/absence metrics. Fish sampling methods will be developed to capture temporal variation and nearshore habitat use (e.g., monthly or bi-weekly from February to August) and multiple sampling methods (e.g., beach seine, lampara netting, snorkel/SCUBA). However, we should note that our sampling design will not distinguish rearing from migratory use of sites, given that samples will represent spot measurements at paired sites, or origin of fishes, given that nearshore habitats can represent a mixing zone for multiple populations.

Pilot Study
The Pilot Study will focus on testing and refining physical (mapping) and biological monitoring methods to ensure that they can be applied to the entire population of sites. We will begin pilot data collection in late winter to early spring of 2023 to capture peak salmon out-migration and forage fish use at the sites. This information will be used to refine the monitoring and sampling plan as well as inform the field implementation and sampling at all sites in the next phase of the project (Phase 2). The number of sites that are sampled during pilot implementation will be limited and not intended to provide data to support statistical analyses to test study hypotheses. However, the data collected during pilot implementation could be used to inform evaluation of sample sizes using power analyses of variance measures for target metrics.

Notes[edit]

Please contact Jason Hall (jason.hall@fishsciences.net) or Shelby Burgess (shelby.burgess@fishsciences.net) with any questions regarding this project.

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