Birch Bay is a headland bay created by the refraction of incoming waves on the headlands that lie on either side of the bay. 
Birch Bay on a November dayBirch Bay, Washington (Wikipedia) Birch Bay is a protected bay of the east shore of the Salish Sea, between Semiahmoo Bay and Lummi Bay; approximately 100 miles (160 km) north of Seattle and 35 miles (56 km) south of Vancouver, BC, Canada. 
Mount Baker, WA simplified hazards map (usgs.gov)