Headlands divide the Oregon coast into compartments, or littoral cells. Within individual littoral cells, features such as inlets, jetties, and rocky outcrops may define the boundaries of even smaller compartments, or subcells. As many as 21 littoral cells have been identified along the Oregon coast. They range from less than 10 kilometers to over 100 kilometers in length. The sandy shoreline encompassed within these cells represents about 262 of the 362 miles, or 72 percent, of the Oregon coast. Approximately 45 percent of these sandy shores are dune-backed, with the remainder being bluff-backed or occupied by inlets.
Ideally, littoral cells or subcells define closed compartments in terms of sand supply. The headlands restrict transfers of onshore sediment to offshore movements within individual littoral cells. These internal exchanges are typically described in terms of contributions to or losses from the littoral cell sediment budget. Thus, erosion or accretion along any given segment of shoreline is reflected in the balance of the budget.
Rivers, bluffs, dunes, and the inner shelf have been identified as potential sources of sediment within Oregon coast littoral cells. Bays, dunes, the offshore, dredging and mining sites have been identified as potential sinks. It is known that combinations of sources and sinks, as well as absolute budget balances, differ markedly between individual cells along the Oregon coast. However, detailed sediment budgets of individual cells do not exist.
These concepts have important management as well as scientific implications. For example, they suggest that efforts to alleviate hazards along one segment of shoreline have the potential to adversely impact other segments of shoreline within the same littoral cell. Further, they suggest that maintaining an adequate littoral cell sand supply is an important objective. This is because maintenance of an adequate sand supply, and hence a wide sandy beach, not only provides benefits from the standpoint of hazard alleviation, but it also enhances recreational, scenic, and in turn, economic opportunities.