Saturday, March 08, 2014

The Portage

Portage is one of those names that crops up in many different places - but the three that come to mind on Puget Sound (I'm not counting Portage Bay below UW) are all tombolos, or at least were tombolos at one time). All three were places where simply lugging your canoe over the beach berm saved you several miles of paddling in rough water.

One of these is at the tip of the Lummi Peninsula at the north end of Bellingham Bay, where a spit (really just a bar, but that's another story - one I don't know) connects to Portage Island. Another is the passage between Indian and Marrowstone Island, which was closed by a barrier beach until the Corps of Engineers excavated the channel and built jetties early in the 20th century.

The third is this low isthmus that connects (or separates, depending on your perspective) Vashon and Maury Islands. As with all of these, there is always some debate about whether historically there was an open channel, but in general, maintaining a channel in these situations would be difficult, as the beach would tend to close up the gap pretty quickly. There has to be a pretty strong tidal differential to maintain enough flow to keep something like this open (or a complete lack of sediment).  That doesn't mean that sometimes storm waves and high tides would not have periodically washed over the top, but that's not the same as a navigable connection unless you're in a kayak and willing to do battle with the logs.


The north side of this tombolo would have been the primary berm since the exposure is greater and there is much more robust beach.  The south side lies within Quartermaster Harbor and is fairly sheltered.  Typically, in a situation such as this, the wetland that formed in association with the tombolo would have drained to the southern, more protected side.  Trails across these features become roads and a desire to maintain access during storm conditions leads them to be elevated and armored.  Here, it's still only a short hop from the beach on the north side of the road to the remaining wetland on the south side.  And the south side, like any south-facing beach at the north end of an embayment on Puget Sound, is a magnet for anything that floats and blows across the surface of the water.  Logs, old styrofoam floats, plastic water bottles, sneakers, tennis balls.


Two weeks ago (I hope readers don't think this blog is live - or even almost live), I was on Vashon to give a talk and had a chance to swing by Dockton, where another small restoration project has just happened.  For the "before," check out my post from a few years ago:

Dockton: May 2008

Note that the restoration project is just west of the boat ramp and county park - there is another, larger restoration project just waiting to happen under that parking lot!

The county has recently pulled out the old riprap and excvated an s-shaped channel to capture the upland runoff.  The hydrology may be defined as much by culverts under the road (which lies just uphill) as by the original stream network.  The result is a small stream mouth estuary - or what will become one. Besides the channel, the beach berm has been reshaped to form a small spit.  Waves (what few there are here) and tides will spend a year or two reshaping the berm, but the bulk of the changes from here on out will be in the vegetation and in what ever fauna choose to colonize or pass through.  It will be fun to watch.