Archeological evidence indicated the spit has developed across Drayton Harbor over the last 4000 to 5000 years (Grabert & Schwartz, 1972).
At the northern most reach of Whatcom County’s shoreline is a spit approximately 2000 meters long trending northeasterly from the north side of Birch Point (fig.2.). The spit separates Drayton Harbor from Semiahmoo Bay and provides some protection for small boats and shoreline developments within the bay.
Semiahmoo Spit is a low depositional feature rising approximately two meters above mean high water. Its low undulating sandy surface is covered with beach and grass scattered trees.
The northeasterly growth of Semiahmoo Spit indicates that sediment eroded from Birch Point has been transported by littoral drift northward, leading to the growth of the spit.
It [Semiahmoo Spit] is only thirty to forty meters wide along its southern connection with Birch Point. High storm waves frequently overtop this area limiting access to the spit. Toward the northeastern end, the spit gently broadens to nearly three hundred meters, and appears to be quite stable.
