Saturday, June 28, 2008

Homer Spit

What an elegant concept - a long, sinuous spit extending out across Kachemak Bay towards the snow covered peaks of the Kenai Range. From the hills above town the concept holds up well. Down on the spit, the elegance of the concept is blurred a little bit by the frontier-style development.

The beaches consist of sand and gravel transported from bluffs along Cook Inlet northeast of town (Bishop's Beach), but the foundation of the spit may be a moraine left by a glacier that once reached this far down Kachemak Bay.

In the 1964 earthquake, the spit, along with most of the Kenai Peninsula, dropped several feet. This pretty much neutralized any dry land on the spit's backshore, so most of the dry ground found today is the consequence of an enormous amount of fill added on top since then.

The spit is a five-mile long riprapped causeway with acres of parking lots, souvenir shops, and fish packing operations, plus a large marina and numerous port facilities. Some of the tourist places and restaurants are on piles hanging over the beach, as are some brand new condos near the tip. There were folks camping all along the beach - one of several scenes that contributed my image of Alaska beaches as gravel backshores lined with RVs.

I'd love to know more about how the shoreline has responded in the 44 years since the earthquake. Subsidence reduced the size of the spit and in the absence of human intervention, would have resulted in the shoreline shifting tens or hundreds of feet landward, but at the same time, subsidence might also have led to dramatic increases in updrift bluff erosion and the potential for a big pulse of new sediment to move towards the spit. I wonder if the multiple gravel berms on the outer face of the spit can be attributed in part to decades of earthquake-induced sediment supply?

The spit was equipped with tsunami sirens, but I doubt most of the folks on the spit would know what to do if they went off. At 3PM on a summer afternoon, as the halibut boats pull in and the gift shops are full and the ferry is unloading, the evacuation might be tricky. By the time people got the awning rolled up and the satellite dish folded away, the RV would already be floating upside down in the marina.

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