King County's 1996/1997 Beach Assessment

Seahurst Park, Burien

Site Description

Seahurst Park was a King County Park until 1996 when it was given to the new city of Burien. The beach itself is about 2,000 feet long and is comprised mainly of finer material than most of the beaches surveyed. The upper beach has been stabilized with a sea wall for most of its length. There are several pipes which discharge water onto the beach. The luxuriant growth of Enteromorpha sp., a green seaweed that grows in a ribbon like form, indicates that the flow from those pipes is constant. The discharge from one of the pipes is such that the pipe seems to be conveying a tight-lined stream rather than seepage. Recently, the upper beach has been modified through the placement of large logs, plantings of native vegetation and chunks of rip-rap. The purpose of those materials is to restore a natural appearance and to limit access to the beach.

Intertidal Inhabitants

There was no formal invertebrate survey of this beach as it was added to the list late in the season.

Clams

The clam band covered about 3.5 acres. Thirty-six (36) holes were dug but only 25 contained one or more clams. Numerically, most of the clams were found on the along the 200 foot, 300 foot and 400 foot transects which began at the south end of the beach. Numerically, the macoma clams comprised about half of the clams and the littlenecks 19%. By weight, the littlenecks comprised about half of the biomass and macomas comprised about 25%.

Check out the following graphs for more information about the clam population:
Numeric composition of clam population
Weight composition of clam population
Numeric distribution of clam population
Biomass distribution of clam population

The clams here were scarce and very small; 188 clams weighed about 1.2 grams each. The density estimate of 8 clams per square foot was the second lowest of the beaches, yielding about 9.2 grams per square foot the lowest yield of all of the beaches surveyed.

Of the eight manila clams, 36 littleneck clams and 37 butter clams collected in our survey, none were of legal size. The manila, littleneck, butter, macoma and softshell clams and the cockles were all smaller than the averages for all beaches combined. At best, the clams found here were one third the averages.

Seaweed

No marine algae survey was conducted for this site.

Use

The beach appears to have been thoroughly picked over. All of the boulders have been overturned so often that they have dead barnacles on all surfaces. The sediments throughout clam band show evidence of disturbance. Most telling is the absence of clams, even in areas of what appears to be prime habitat.

The scarcity and small sizes of the clam species indicate that this beach has been over harvested. If the obstructions at the access points are left in place and if harvesting activities can be limited for two to three years, the population should recover.

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Updated: 11/02/98