Event Title

Arrested development at Ala Spit, Whidbey Island – Impacts of development on coastal processes, habitats, and park use and restoration design

Presentation Abstract

Ala Spit is a 2,000 ft long gravel and sand spit on northeast Whidbey Island in Skagit Bay, WA. The spit contains a mosaic of habitat types, including a barrier estuary and lagoon. Features include salt marsh, a stream, mudflat, and forage fish spawning beaches. The site is also an Island County Park with high use for beach walking, bird watching, and fishing. The spit and estuary have been the subject of study and design to try to prohibit impacts to back barrier and spit habitats cause by impacts of up-drift development. The driving force for WRIA 6 in initiating a project was the potential breaching of the spit as associated changes to the estuary and lagoon. In an attempt to address the reduction in the width and elevation of the neck of the spit, the first phase of design and structure removal occurred. However, overwash and substantial spit lowering accelerated and a partial breach has progressed dramatically in the last few years. Island County Health Department contracted Coastal Geologic Services to complete a feasibility study for removal of an up-drift groin and bulkhead. A coastal processes assessment of the spit was required, along with a slope stability assessment of nearby residential houses above a bluff. The remaining large groin was identified as the critical structure which needed to be removed to restore upper intertidal littoral transport. The study resulted in the development of a detailed conceptual design for removal and of both structures and installation of a much smaller and relocated groin, in addition to reconfiguring the parking lot, reconnecting salt marsh, and substantial beach nourishment to attempt to turn back the clock at the neck of the spit. Results of the littoral drift assessment, impacts of structures, changes at the neck of the spit, and details of the design which is currently in development) will be presented in the poster. Ala Spit and its many modifications is a microcosm of impacts to littoral drift at Salish Sea spits and barrier estuaries, and serves as an example of the analyses and actions needed for process-based restoration to allow for a return to the natural evolution (“normal development”) of the spit and the barrier estuary.

Session Title

Session S-01G: New Strategies for Shorelines

Conference Track

Shorelines

Conference Name

Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)

Document Type

Event

Start Date

1-5-2014 5:00 PM

End Date

1-5-2014 6:30 PM

Location

Room 6C

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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May 1st, 5:00 PM May 1st, 6:30 PM

Arrested development at Ala Spit, Whidbey Island – Impacts of development on coastal processes, habitats, and park use and restoration design

Room 6C

Ala Spit is a 2,000 ft long gravel and sand spit on northeast Whidbey Island in Skagit Bay, WA. The spit contains a mosaic of habitat types, including a barrier estuary and lagoon. Features include salt marsh, a stream, mudflat, and forage fish spawning beaches. The site is also an Island County Park with high use for beach walking, bird watching, and fishing. The spit and estuary have been the subject of study and design to try to prohibit impacts to back barrier and spit habitats cause by impacts of up-drift development. The driving force for WRIA 6 in initiating a project was the potential breaching of the spit as associated changes to the estuary and lagoon. In an attempt to address the reduction in the width and elevation of the neck of the spit, the first phase of design and structure removal occurred. However, overwash and substantial spit lowering accelerated and a partial breach has progressed dramatically in the last few years. Island County Health Department contracted Coastal Geologic Services to complete a feasibility study for removal of an up-drift groin and bulkhead. A coastal processes assessment of the spit was required, along with a slope stability assessment of nearby residential houses above a bluff. The remaining large groin was identified as the critical structure which needed to be removed to restore upper intertidal littoral transport. The study resulted in the development of a detailed conceptual design for removal and of both structures and installation of a much smaller and relocated groin, in addition to reconfiguring the parking lot, reconnecting salt marsh, and substantial beach nourishment to attempt to turn back the clock at the neck of the spit. Results of the littoral drift assessment, impacts of structures, changes at the neck of the spit, and details of the design which is currently in development) will be presented in the poster. Ala Spit and its many modifications is a microcosm of impacts to littoral drift at Salish Sea spits and barrier estuaries, and serves as an example of the analyses and actions needed for process-based restoration to allow for a return to the natural evolution (“normal development”) of the spit and the barrier estuary.