Semiahmoo Spit - Geomorphology and Geography

Geomorphology and Geography

It is oriented toward the northeast, which means the direction of longshore drift, a constructive geomorphologic process, is northeasterly. Longshore drift through the Strait of Georgia, therefore, tends to be northeasterly. Because waves are mainly powered by wind, the waves approaching Semiahmoo hit the shore obliquely, at an angle of approximately 30 to 45 degrees to the northeast, and thus the prevailing wind through the Strait of Georgia must also be northeasterly. Because of longshore drift, sediments are picked up from the headland and deposited according to size and based on wave energy. High energy wave action can carry large sediment, such as cobbles and gravel, but only as long as the energy exists. Since the waves repeatedly hit the shore, energy is lost, and so larger, denser sediments are quickly deposited near the headland. Smaller, less dense sediment, such as gravel, sand, mud, and clay, can be carried and deposited farther away from the headland because they do not require as much energy for transport. One mile to the north of the tip of the spit is the border between the United States and Canada. Approximately four miles to the northeast of the tip of the spit is the city of White Rock, British Columbia. The spit is approximately 1.25 miles (2.01 km) long and contains approximately 125 acres (0.51 km2) of land.