Event Title

Coastal Zone Mapping along the Elwha Drift Cell, Central Strait of Juan de Fuca

Presentation Abstract

During the summer of 2015, the Washington State Department of Ecology Coastal Monitoring & Analysis Program (CMAP) conducted two surveys to map the beaches, bluffs, and nearshore region of the Elwha Bluffs and Ediz Hook coastline in the central Strait of Juan de Fuca near Port Angeles, Washington. This work, funded by the US Army Corps of Engineers, provides the ability to assess shoreline change within one season over a 4-month timespan. High-resolution topographic and bathymetric data was collected using boat-based lidar and dual-head multibeam sonars aboard the R/V George Davidson, with additional topographic data collected by foot using GPS on backpacks to fill in shadows from the lidar and walk cross-shore transects. By employing these methods, seamless coastal zone mapping from bluff top to over 10-m water depth was achieved. These data sets represent the first ever drift-cell scale comprehensive and detailed mapping of both coastal bluffs and the nearshore. Together, the surveys enable assessment of bluff sediment supply to beaches and the dispersal of sediment through the nearshore zone. While the interval between surveys was relatively short, significant human-induced and natural erosion of the Elwha bluffs was observed between June and October. In particular, the massive reshaping of the bluff face and uplands at the Port Angeles landfill (still in progress) provides snapshots of prior conditions of the bluff, beach, and associated seawall along a portion of the project site. These data also provide an essential baseline for assessment of anticipated increased littoral sediment supply resulting from the removal of the Elwha dams and can be used in conjunction with previous nearshore and beach profile data collected by the US Geological Survey and CMAP before and after dam removal. The change analysis to date suggests sediment from the delta is beginning to make an imprint in the nearshore fronting the Elwha bluffs, with sand blanketing lower intertidal cobbles and initiating the choking of kelp beds.

Session Title

Long term studies reveal the complex dynamics and interconnectivity of the physical, geomorphic, biological systems of Salish Sea shorelines and how these systems interact with social and political systems

Conference Track

Shorelines

Conference Name

Salish Sea Ecosystem Conference (2016 : Vancouver, B.C.)

Document Type

Event

Location

2016SSEC

Type of Presentation

Oral

Contributing Repository

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

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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Coastal Zone Mapping along the Elwha Drift Cell, Central Strait of Juan de Fuca

2016SSEC

During the summer of 2015, the Washington State Department of Ecology Coastal Monitoring & Analysis Program (CMAP) conducted two surveys to map the beaches, bluffs, and nearshore region of the Elwha Bluffs and Ediz Hook coastline in the central Strait of Juan de Fuca near Port Angeles, Washington. This work, funded by the US Army Corps of Engineers, provides the ability to assess shoreline change within one season over a 4-month timespan. High-resolution topographic and bathymetric data was collected using boat-based lidar and dual-head multibeam sonars aboard the R/V George Davidson, with additional topographic data collected by foot using GPS on backpacks to fill in shadows from the lidar and walk cross-shore transects. By employing these methods, seamless coastal zone mapping from bluff top to over 10-m water depth was achieved. These data sets represent the first ever drift-cell scale comprehensive and detailed mapping of both coastal bluffs and the nearshore. Together, the surveys enable assessment of bluff sediment supply to beaches and the dispersal of sediment through the nearshore zone. While the interval between surveys was relatively short, significant human-induced and natural erosion of the Elwha bluffs was observed between June and October. In particular, the massive reshaping of the bluff face and uplands at the Port Angeles landfill (still in progress) provides snapshots of prior conditions of the bluff, beach, and associated seawall along a portion of the project site. These data also provide an essential baseline for assessment of anticipated increased littoral sediment supply resulting from the removal of the Elwha dams and can be used in conjunction with previous nearshore and beach profile data collected by the US Geological Survey and CMAP before and after dam removal. The change analysis to date suggests sediment from the delta is beginning to make an imprint in the nearshore fronting the Elwha bluffs, with sand blanketing lower intertidal cobbles and initiating the choking of kelp beds.