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.
Coastal Processes of the Whatcom County Mainland (dnr.wa.gov)Numerous natural erosional and depositional processes operate upon shorelines to create a diversity of coastal landforms. Waves are among the most important causes of this diversity as they remove, build, and shape beaches and sea cliffs.
Whatcom County Shorelines (figure 1)