Kayak Point, Washington Restoration Feasibility and Design: Sea Level Rise Projections
Coastal Geologic Services (CGS) was contracted by Snohomish County in 2008 to provide restoration feasibility assessments and propose restoration scenarios for Kayak Point County Park in Washington State. Infrastructure at Kayak Point had been damaged by recent winter storms and managers were concerned that sea level rise could alter existing ecosystems. Restoration scenarios considered the effects of sea level rise, storm intensity, and shifts in sediment depositional rates.
In 2007, Snohomish County Government funded CGS to conduct a coastal geomorphic assessment and restoration feasibility study of Kayak Point County Park. The study was prompted by damage to park infrastructure (roads and picnic shelters) and altered shorelines from recent winter storms. The results of this study were used to design restoration alternatives to enhance the resilience of the park to future winter storms and sea level rise. To assess changes in coastal geomorphology along Kayak Point’s shoreline, current shoreline conditions were qualified and compared to historic shoreline conditions using ArcGIS software and field research.
The current shoreline was characterized by categorizing segments into six groups by visual inspection:
- Feeder Bluff Exceptional - rapidly eroding bluff-segments
- Feeder Bluff – substantial sediment input
- Transport Zone – net shore-drift sediment is merely transported alongshore
- No Appreciable Drift – no net volume of sediment transport
- Modified – areas that have been bulkheaded or otherwise altered
- Accretion Shoreform – depositional environments
Areas currently listed as “modified” were analyzed to determine their prior state using historical aerial photos. All other mapped shoreline conditions were assumed to be the same in the historic comparison. Shore change analysis was conducted by comparing the current shoreline map and erosional trends to the pre-developed, historical map.
Beaches at Kayak Point are primarily composed of gravel and sand. Sediment transport is primarily due to wind-generated waves during intense winter storms. Bulkheading, or the hardening of shoreline, has occurred along roughly 38.8% of the 9.6 mile long shoreline. The bulkheads have reduced sediment input from eroding beach bluffs by roughly 29% relative to historical norms, causing the southern, down-drift beaches, to erode. Accelerated sea level rise is expected to increase erosion rates at Kayak Point thereby displacing ecosystems and increasing the vulnerability of existing infrastructure. Hardened shorelines due to bulkheading will hinder the system’s ability to transgress, or migrate landward, in response to heightened sea levels. Removing bulkheads can create space to enable shoreline transgression; this concept is referred to as “managed retreat” or “managed realignment.”
CGS developed three restoration scenarios for Kayak Point ranging from minimal, moderate and substantial change to enhance the resilience of the park. The goals of the restoration scenarios were to eliminate ongoing habitat degradation, repair the park’s road, and protect existing picnic shelters. Restoration techniques vary in extent of bulkhead removal and amount of distance the road is relocated inland. The three scenarios were presented to Snohomish County government in 2008 and Phase II of the project will be the implementation of the selected restoration scenario.
The Kayak Point Restoration Plan was funded by Snohomish County Surface Water Management. The contract was competitively awarded to CGS.
Outcomes and Conclusions
Restoration of Kayak Point is expected to begin in 2010 in collaboration with community members, local government officials, and the Puget Sound Partnership.
Feifel, K. (2010). Kayak Point, Washington Restoration Feasibility and Design: Sea Level Rise Projections [Case study on a project of Coastal Geologic Services]. Product of EcoAdapt's State of Adaptation Program. Retrieved from CAKE: http://www.cakex.org/case-studies/kayak-point-washington-restoration-fea... (Last updated January 2010)