Presentation Abstract

This oral presentation focuses on extensive recent work documenting long-term coastal bluff recession rates along the shores of the Puget Sound region of the Salish Sea. Coastal bluffs are the most prevalent coastal landform type in this region, accounting for over 1,000 miles (42.6% by length) of the region’s shore (CGS 2017). Coastal bluff recession supplies the overwhelming majority of sediment to Puget Sound beaches, which comprise valued nearshore habitats for salmon, shellfish, and other fish and wildlife (Finlayson 2006; Johannessen and MacLennan 2007; Keuler 1988). Little research has documented the range of bluff recession rates in the region (less than 25 published sites; Shipman 2004, 1995) or how those rates are influenced by changes in bluff form, geology, stratigraphy, or wave exposure. Understanding the range and dominant drivers of long-term (23–101 years for this project) coastal bluff recession rates is critical in informing coastal management and the prioritization and design of restoration and conservation projects. These data may be also used to identify future risk. CGS compiled existing historical change rates into a database, which was then augmented with additional field (direct measurement) and remote (using aerial photography) measurements, totaling 185 sites across the region. Variables describing various bluff characteristics were compiled for all measurement locations and further explored. Variables included: bluff height, surface geology, toe geology, maximum fetch, shore orientation, geomorphic shoretype, beach substrate, tidal range, latitude, permeable over impermeable stratigraphy, location within the drift cell (percent down‐drift of the littoral drift cell origin), and vertical land movement. This presentation will showcase the database of coastal bluff recession rates throughout the U.S. Salish Sea, including the project methods, analysis, and results. Future work includes refining existing datasets and adding new bluff sites for a more spatially distributed and representative picture of long-term shoreline change in the region.

Session Title

Challenges and Solutions for Shoreline Armor Removal and Design of Soft Shore Protection: Part II

Keywords

Bluffs

Conference Track

SSE1: Habitat Restoration and Protection

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE1-316

Start Date

4-4-2018 4:15 PM

End Date

4-4-2018 4:30 PM

Type of Presentation

Oral

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 4th, 4:15 PM Apr 4th, 4:30 PM

An assessment of long-term bluff recession rates in the Puget Sound and Salish Sea: implications for the prioritization and design of restoration projects

This oral presentation focuses on extensive recent work documenting long-term coastal bluff recession rates along the shores of the Puget Sound region of the Salish Sea. Coastal bluffs are the most prevalent coastal landform type in this region, accounting for over 1,000 miles (42.6% by length) of the region’s shore (CGS 2017). Coastal bluff recession supplies the overwhelming majority of sediment to Puget Sound beaches, which comprise valued nearshore habitats for salmon, shellfish, and other fish and wildlife (Finlayson 2006; Johannessen and MacLennan 2007; Keuler 1988). Little research has documented the range of bluff recession rates in the region (less than 25 published sites; Shipman 2004, 1995) or how those rates are influenced by changes in bluff form, geology, stratigraphy, or wave exposure. Understanding the range and dominant drivers of long-term (23–101 years for this project) coastal bluff recession rates is critical in informing coastal management and the prioritization and design of restoration and conservation projects. These data may be also used to identify future risk. CGS compiled existing historical change rates into a database, which was then augmented with additional field (direct measurement) and remote (using aerial photography) measurements, totaling 185 sites across the region. Variables describing various bluff characteristics were compiled for all measurement locations and further explored. Variables included: bluff height, surface geology, toe geology, maximum fetch, shore orientation, geomorphic shoretype, beach substrate, tidal range, latitude, permeable over impermeable stratigraphy, location within the drift cell (percent down‐drift of the littoral drift cell origin), and vertical land movement. This presentation will showcase the database of coastal bluff recession rates throughout the U.S. Salish Sea, including the project methods, analysis, and results. Future work includes refining existing datasets and adding new bluff sites for a more spatially distributed and representative picture of long-term shoreline change in the region.