Saturday, July 06, 2013

Tramp Harbor

Tramp Harbor lies on the eastern shore of Vashon Island, just south of Ellisport and Point Heyer (KVI Beach), and just north of the Portage, the narrow isthmus (historically, a tombolo) that connects Vashon and Maury Island.


Like many other early roads on Puget Sound, Dockton Road (George Edwards Road on some maps) was built on the beach. It was fairly simple to construct above normal high tides - often on piles, later on fill - and it was certainly easier than the alternative, which was building roads through steep, unstable, and heavily forested terrain.

These shots capture a simple point about bulkheads and beach fill. While most walls bury the uppermost beach and tend to isolate the marine and terrestrial environments, some transform the beach much more than others.

These walls all differ in their waterward extent, which is as much about the amount of fill behind them as about the character of the wall itself.  The first picture shows the base of the old wharf/pier, a rectangular mole extending to mid-tide (not counting all that rock dumped in front).  Not much beach!

This next one shows the roadway itself, protected by an old wood bulkhead.  The upper beach is missing - along with the drift logs and the natural bluff toe.  Old riprap and quarry spalls cover what's left of the beach.

The following photo shows a section of wall that was replaced a number of years ago.  Still no upper beach, but the design reduces the impact on the beach somewhat, and some of the rock debris on the lower beach has been cleaned up.

The last picture is a residential rock seawall at the north end of the bay. It is fairly typical of modern era bulkheads on Puget Sound.  It was built closer to the toe of the bank, so its immediate impact on the beach is certainly less than the ones described above. But it still eliminates the upper beach, so no drift logs and none of the natural riparian zone that would have once been observed.  They lock up sediment on the beach and prevent new sediment from being delivered by erosion.  And unlike roads on the beach, these residential structures are much more widespread and are still being built.  Regardless of their individual impacts, their aggregate influence on Puget Sound beaches can be significant.

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