Saturday, March 22, 2008

Dean's Point

Named after an early resident, this low point of land on western Samish Island is now Camp Kirby.

Cuspate forelands generally occur on shorelines where there is significant wave action from two, nearly opposite directions. This leads to converging longshore sediment transport, which in turn forms a triangle (cusp) of low land in front of the coastline (foreland). They are often assymetrical, due to differences in wave regime, sediment supply, or coastline orientation. They usually have wetlands or lagoons in the middle, sometimes with a tidal inlet along one side (what I call a limb). The assymetry also applies to the long-term evolution of the feature. Many are eroding on one limb and accreting or stable on the other, leading to gradual shifting in the shape or position of the landform.

The northwest beach is steep. The storm berm is narrow and is rolling back across the lower ground behind it. The vegetation line is distinct and relatively straight. There are few drift logs. The berm crest appears to be slightly higher than the berm on the southeast side. It looks like this beach has more gravel and less sand than the beach on the other side. I suspect this beach sees fewer, but perhaps bigger, storm waves. It is drift-aligned (oblique to waves and extending in the direction of drift).

The southeast beach is flatter. There are multiple berms and they are less distinct than the one on the north side. The backshore and the berms are covered with drift logs (typical of south-facing beaches on the Sound). In map view, this beach is concave seaward and is swash-aligned - oriented perpendicular to the greatest fetch. As a result, the southeastern limb acts like a big pocket beach. There is no place for the gravel and coarse sand to go. It may get more frequent wave action than the other side, but it may also be broadening.

Thursday afternoon the winds were blowing from the south, breaking parallel to the south beach and refracting around the point to break northward along the northern beach. At the very tip of the spit, the waves were actually breaking against each other from opposite directions.

The pill box at the end was reportedly built to serve as a shooting blind, but now is a rectangular tide pool in which eagles have apparently drowned. A historic relic that might be better off gone?

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