Westport, WA - A long-term plan for Westport's South Jetty could be asking for public input early next year.
The modified current practice was detailed to Port Commissioners yesterday, which would rebuild the South Jetty 500 feet to the East of it's current location "That point where the jetty ends is tied to the shoreline position on Halfmoon Bay, so if we extend it to the East we have a wider dune with lower risk of breaching in the future." Coastal Engineer David Michalsen said studies showed surfing at Half Moon Bay would not be impacted by the change in surf. Once approved some time next year, the Port will take the plan public and begin assessing construction costs.
Following construction of the Grays Harbor South Jetty in the early 1900s, South Beach grew seaward. As the jetty deteriorated, a spit developed at Pt. Chehalis. After the jetty was repaired, the spit and the beach near the jetty eroded, forming Halfmoon Bay. During the 1950s, South Beach began to erode. But repairs to the South Jetty did not halt erosion.
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Waves erode the beach near the South Jetty
In 1993, storm waves plowed through Westhaven State Park into Halfmoon Bay, threatening Westport's wastewater treatment plant, aquifer, and sewer outfall.
- Ongoing erosion and repairs
In 1994, the US Army Corps of Engineers filled the eroded area at Westhaven State Park with 600,000 cubic yards of dredged material. The erosion continued; waves washed away 10,000 cubic yards of sand per year from the site. In 2002, the US Army Corps of Engineers filled the eroding site again. Repairs to the beach totaled nearly $12 million.
What's happening near the South Jetty?
- High wave energy
Wave action is too intense for sand to build up. As waves bounce and refract around the Grays Harbor ebb-tidal delta, they focus energy. The steep slope of South Beach also allows bigger waves to break closer to shore.
- Summer sand loss
During the summer, sand is carried south along beaches by littoral drift.The Grays Harbor entrance, delta, and jetties may block this flow of summer sand, reducing the sand supply.
- Winter sand loss
During the winter, sand is carried north along beaches by littoral drift.The South Jetty may interrupt this flow of winter sand, decreasing the sand supply to Halfmoon Bay.
- Small offshore bars
Offshore bars help buffer beaches against pounding wave action. Near South Beach however, offshore bars are relatively small.