channel mouth bar
When a river enters an ocean or lake, losing velocity, its sediment load drops to the bottom and forms a bar. This underwater ridge may lie anywhere from the river mouth to twenty miles or more out to sea. If daily sea-level ﬂuctuation is small, waves breaking along a stable line may reinforce the bar. Materials deposited at the outﬂow of an estuarine stream disrupt currents and form a barrier to navigation. The formidable bar of the Columbia River discouraged explorers from entering the “Great River of the West” for many years, until Captain Robert Gray crossed it in the Columbia Redeviva on a mild May day in 1792. Since then, the Columbia River Bar has claimed scores of ships and become known as “the graveyard of the Paciﬁc.” Today skilled bar pilots, separate from the regular river pilots, guide large vessels over the bar. Tennyson’s famous elegy “Crossing the Bar” makes spiritual metaphor from the mud that challenges every outbound journey.