Thursday, May 02, 2013

Hood Canal Bridge

The western end of the Hood Canal  bridge is built on fill and extends across the beach.  The result has been some fairly obvious changes to sediment transport and beach processes both north and south of the approach (Shine Tidelands 2007, Termination Point 2011).  But here on the eastern end, the bridge passes over the beach and any effects on the beach are less obvious.  I've speculated a little about the possible effect of the bridge on wave action north of the bridge in an earlier post on Salsbury Point (2007).


The beach continues unbroken beneath the bridge, although the character of the low tide terrace changes significantly along here and there is also a small accretional bulge in the upper beach a short distance north of the bridge.  The low tide beach is likely a fairly robust feature of the landscape - it would be very difficult, short of dredging, to change the width of the low tide terrace very much.  But the upper beach is a different story and I've always wondered whether the accretion might be in part to the falling off of wave action from the north due to the bridge itself.  There was already a fairly wide beach here -- and a much older dock -- before the bridge was built in 1961, so this would require some serious sleuthing to sort out.

Under the bridge, WashDOT (I assume) has placed a series of nicely arranged logs at the base of the slope. This is one of numerous examples on Puget Sound where large wood is being used in a naturalistic way as erosion control. I'm often pretty skeptical of such approaches (long story, but sometimes I think they are neither very effective nor very natural), but in this case it's an interesting idea.  Admittedly, I'm not sure how much of an erosion problem there was to start with at this location.

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