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Oregon Beach and Shoreline Mapping and Analysis Program: Pacific Northwest Estuaries and Shores  

In recent years, the northern Oregon coast has experienced a recurrence of significant erosion in part due to the occurrence of the major 1982-83 and 1997-98 El Niņos (Komar 1986, 1998), which resulted in "hotspot" erosion at places like Neskowin, Cape Lookout State Park, and near "The Capes" development (north of Netarts bay mouth), but also in response to the large ocean waves that were observed during the late 1990s, which severely eroded the shore adjacent to the town of Rockaway (Allan and Komar 2003).  For example, prior to 1996 researchers had estimated the 100-year storm wave to be about 10 m (33 ft).  However, since 1997 the Oregon coast has been subjected to the equivalent of nine 100-year events.  Revised estimates of the 100-year storm wave now place it at around 15 - 16 m (~50 ft) (Allan and Komar 2001).  This raises several questions including:

  • Why are we experiencing larger waves now?

  • Can we expect to see large waves in the future?

  • Are these changes part of natural climate cycles or are they a product of climate change?

  • How often do these erosion events occur and how quickly do the beaches respond to the large wave events?

  • How quickly do the beaches recover following erosion episodes?

  • What is the best form of shoreline protection to use?

  • How do coastal managers effectively plan for such events? and many more.

The development of a comprehensive beach and shoreline change observing network along the Oregon coast provides scientists, coastal managers, the geotechnical community, and the public at large with the necessary information to understand the impacts of storms on the coast, and the potential future impacts associated with climate change.  Such information may be eventually used to develop appropriate coastal hazard zones, which provides guidance to the public about where to build or not to build on the coast.

 

Study objectives

  1. Maintain the core elements of the existing beach monitoring programs on the Oregon coast, which includes:

    • undertaking quarterly beach surveys in the Neskowin (15 sites) and Rockaway littoral cells (25 sites), and along the Clatsop Plains (6 sites);

    • undertake biannual surveys of profiles established in the Newport (58 sites) and Beverly Beach littoral cells (15 sites); and,

    • if feasible, update monitoring effort following an extreme storm(s).

  2. Working with Dr. Peter Ruggiero from the Dept. of Geosciences at Oregon State University, initiate pilot bathymetric surveying along the Rockaway littoral cell;

  3. Undertake beach surface mapping at three locations along the Rockaway littoral cell to document the 3-Dimensional response and morphodynamics of the beaches.  These surveys are carried out on an annual basis;

  4. Working with Dr. Peter Ruggiero from the Dept. of Geosciences at Oregon State University, undertake probabilistic shoreline change and cross-shore modeling in the Rockaway littoral cell in order to quantify the effects of climate change and variability (variations in wave approach, El Niņos, PDO, secular increases in wave heights) on shorelines;

  5. Compare the measured profile responses with known forcings derived from offshore wave buoys and wave runup model simulations; and,

  6. Disseminate beach state-change data and products among coastal managers, regulatory authorities and the public at large.  Beach state data (i.e. beach slope, beach crest elevation, dune toe location etc.) will be extracted from the beach profiling and surface mapping to enhance the conceptual understanding of OR-WA beaches and refine existing predictions of  future coastal change and hazards.

The Beverly beach littoral cell in Lincoln County.

A house perched precariously close to an eroding bluff at Cove Beach, Clatsop County.

 

 

 

References:

Allan, J.C. and P.D. Komar, 2001, Wave climate change and coastal erosion in the US Pacific Northwest: Proceedings of the 4th Conference on Ocean Wave Measurement and Analysis, WAVES 2001, San Francisco, California, ASCE: 680-690.

Allan, J.C., P.D. Komar and G.R. Priest, 2003, Shoreline variability on the high-energy Oregon coast and its usefulness in erosion-hazard assessments:  Shoreline mapping and change analysis: Technical considerations and management implications,  M. R. Byrnes, M. Crowell and C. Fowler,  Special Issue No. 38: 83-105.

Komar, P.D., 1986, The 1982-83 El Nino and erosion on the coast of Oregon: Shore and Beach, 54(2): 3-12.

Komar, P.D., 1998, The 1997-98 El Niņo and erosion on the Oregon coast: Shore & Beach, 66(3): 33-41.