About Sandy Shores in Oregon

Headlands divide the Oregon coast into sandy shore compartments, or littoral cells. Within each littoral cell, features such as inlets, jetties, and rocky outcrops define the boundaries of even smaller compartments, or sub-cells. As many as 21 littoral cells have been identified along the Oregon coast ranging from less than 10 km to over 100 km in length. The sandy dune backed shoreline within these cells comprise about 262 of Oregon's 362 mile coastline, the remainder being headlands, bluff-backed or inlets.

Littoral cells, or sub-cells, act as closed compartments for sand supply as headlands restrict transfers of onshore sediment to offshore movements within individual cells. These internal exchanges are typically described in terms of contributions to or losses from the littoral cell sediment budget. Rivers, bluffs, dunes, and the inner shelf are potential sources of sediment while bays, dunes, the offshore, dredging, and mining have been identified as potential sinks. The sediment budgets differ markedly for each individual cell along the Oregon coast.

Components of Oregon Sandy Shores

Beaches are gently sloping zones of unconsolidated material that extend landward from the low-water line to a point where there is a definite change in rock type or landform. Sandy beaches are backed by both dune and bluff backed shorelands.

Dune-backed Shores

Dune land includes all areas underlain by loosely consolidated windblown sand. Areas presently being modified by the wind are termed active, and areas stabilized by vegitation are termed stable. Dune backed beaches make up approximately 45% of the Oregon coast.The littoral cell that extends from Heceta Head to Cape Arago contains the Coos Bay dune sheet, a 150 mile long coastal dune accumulation which is the largest in the United States. Other littoral cells characterized by dune-backed shorelines include the Clatsop Plains and the Neskowin cells on the north Oregon coast, as well as the Bandon littoral cell south of Cape Arago & Coquille Point, and in the vicinity of Gold Beach on the south coast.

Bluff-backed Shores

Bluff-backed shores come in many types and are affected by a number of factors, including bluff material composition. Hard headland-forming basalts for example, do not readily give way, while in contrast, soft bluff-forming sandstones and mudstones are highly susceptible to slope movement. The geometry of bluff materials also affects stability, as can winter rains, groundwater seepage, vegetation cover, wave attack and the width of any fronting beach. Bluff-backed shores come in many types and makeup large segments of the central Oregon coast, from Cascade Head on the north to Cape Perpetua. Portions of the south coast, north of Coquille Point and north of Blacklock Point for example, are characterized as bluff-backed shoreline.