NORTH COAST ESTUARIES

An estuary is a dynamic place where ocean waters meet a river and usually create a highly productive environment. Oregon's estuaries are varied and numerous, ranging from the very large Columbia River estuary to the very small Beaver Creek. The State of Oregon adopted an estuary classication system to preserve diversity and assist with wise management of these valuable ecosystems. Estuaries are classified first as major or minor, and then as natural, conservation, shallow draft development of deep draft development.

Estuaries reflect their relationship with the elements that shape them. The common terms used to describe are succinctly defined in The Oregon Estuary Plan Book.

  • River dominated: Some, like the Columbia River, are dominated by the freshwater flow of the river and have relatively small tideland areas.
  • Drowned river mouth: The majority, like Siletz Bay, and Yaquina Bay, are the drowned river mouth variety, where winter's floods discharge high volumes of sediments through the estuary. In summer, seawater inflow dominates the estuary because the streamflow is low.
  • Bar-built: Others, like Sand Lake and Netarts Bay, are "bar-built," where a sand spit creates a separate estuarine environment which receives very little freshwater inflow.
  • Blind: Some of the smaller estuaries, like Elk River and Sixes River in Curry County, are "blind" estuaries where low river flow in summer results in a sand bar completely closing off the mouth of the estuary.