Tuesday, December 13, 2011

Ala Spit

A lesson in overwash.  The frost on this chilly morning highlighted the beautiful overwash fans from past storms, when waves and high tides spilled gravel over the top of the berm and into the backshore.  Some of these probably go back many years or decades; others are brand new.

Since my visit last month (November 11) waves have washed over the newly constructed berm, depositing much of the sand and gravel on the back side of the narrow neck of the spit. The crest of the berm through this area is now only slightly above Mean Higher High Water so this winter's spring highs will continue to flood over the top.  The beach face is flat and littered with scattered large cobbles and small boulders and occasional chunks of concrete that were left from the old riprap.  The large wood that was placed along the temporary berm has largely washed out.

There are some good photos of the tide washing across the spit in the December 5th Whidbey News-Times.

Restoring nature isn't just about removing man made structures and replanting native vegetation; it's also about restoring the physical conditions that created and maintained the landscape in the first place.  This means allowing storms and erosion and natural disturbances back into the picture - the very things we often go to such great lengths to control.  The trouble is that these dynamic processes are difficult to predict and a site that has been altered for a long period of time will only return to its original condition slowly, and even then, is not likely to return in its original position.

Recovery of the berm will take time and it will take sediment.  The first will require patience.  The latter will be a challenge, as the neck of this spit is short on sand (and particularly gravel, since this is what best builds robust berms).  The foreshore appears to have been starved of sand and gravel due to the development of a bar or proto-spit just to the south.  There are also human modifications, including an updrift groin, that complicate the picture. In an ideal world, these other structures might have been removed and perhaps more gravel might have been added to the foreshore to help jump-start a new berm.

I look forward to watching what happens.  Meanwhile, I trust that folks walking on the spit will take care to head back to their cars before high tide - lest their feet or their dog gets wet.


1 comment:

Dave Wenning said...

More good information about this very interesting little spot. I think we will both be keeping an eye on it. Thanks.