Sometimes we take for granted the gorgeous Oregon coast, yet in reality this ever-changing natural resource is susceptible to the environmental factors around it.
For years, experts have been watching its develop-ment and assessing threats to its continued well-being. A report recently published by the U.S. Geological Survey, in cooperation with the U.S. Department of the Interior provides a view into how erosion affects the Pacific Northwest historically and currently.
This report on the coasts of Oregon and Washington is the seventh in a series of studies on historical shoreline change. It relied on the cooperation of several agencies, including the National Oceanic and Atmospheric Ad-ministration (NOAA), which provided topographical maps from the region, indicating years of observation. Also cited, along with others, is the U.S. Army Corps of En-gineers (USACE), which conducted the first national assessment of coastal erosion in 1971, says the study.
“An increase in erosion hazards in much of Oregon may be related to the effects of sea-level rise and increasing storm wave heights,” the report states. Tectonic activity in the coast region plays an important role in changing the coastal environment. The USGS report is comprehensive, detailed and scientific. It is available online for those who wish to further pursue the details, so we merely offer an overview.
We have seen the effects of the winds and tides every year. We have seen how development on the coast impacts currents. History tells us that some of the land was once some 35 miles farther out to sea, and after the Ice Age the ocean came much farther into the mountains and land, breaching even into the Willamette Valley and in Washington to the Puget lowland, the report says.
“Unlike much of the U.S. coast, population pressure on the PNW coast has historically been relatively low,” states the report.
But some population changes have made impacts. Man-made measures such as jetties affect sand deposits and wave action. For example, Bayocean Oregon, a resort built in the early 1900s: A jetty was built to protect it, but the sea transferred sand and changed currents. Mighty storms circumvented the jetty, and the fledgling resort fell into the sea. (See the story of Bayocean at nwboom-erandseniornews.com) Other areas have placed barriers to protect buildings, but the ocean changes to crash them away or reorganize the beaches.
The report relates the an-cient history of Oregon’s coast, including the drama caused by the Ice Age and its effect on the geology of the coastal land.
Volcanic and seismic ac-tivity have greatly affected the coast’s geology. The western coast of Oregon is home to four major faults. The Cascadia Subduction zone inland along the coast is influenced by four plates, which move beneath the earth. These are the Juan de Fuca plate, the Pacific plate and the Gorda plate at sea and the North American plate inland. “The oceanic Juan de Fuca and Gorda plates are moving northeasterly at a relative rate of about 4 centimeters per year (cm/yr), colliding with and being subducted beneath the continental North American plate,” states the report.
The report says that things began to change during “the Pliocene epoch about 5 million years ago.
“At that time, the Coast Range began to emerge from the sea, forming the land of western Oregon and Washington. Therefore, the PNW coast can be thought of as being geologically very young,” states the report.
“With the land’s emer-gence from the sea during the Pliocene epoch (5 million years ago), erosion processes began. Weaker rocks were cut away leaving the more resistant rocks of the Coast Range and the basaltic headlands along the coast.”
The earth’s geological history affects the oceans today. Glaciers did not reach the coast, and therefore didn’t have much of a geological impact. However, several thousand years ago when the glaciers melted, the sea rose rapidly. What we know as the Oregon coast became that way a mere 2,000 years ago.
Neskowin’s sandy beach covers an ancient forest that lived hundreds of years ago where the ocean now ebbs and flows. Its stumps can be seen on Neskowin’s south beach off and on through the years depending on tide changes. Cascade Head towers as south beach’s headland in Neskowin; its basalt struc-ture attests to its solidity against centuries of wave action.
The USGS study divides the Pacific Northwest shore into eight study regions, which are referred to as littoral zones, meaning land water near shore. Starting from the south, they are Southern Oregon, Bandon, Coos Bay, Lincoln County, Tillamook County, Cannon Beach, Columbia River and the Olympic Peninsula. There are many sub-cells within the regions.
Probably the most prone to change is the Columbia River zone, which affects the shorelines of both Oregon and Washington. However, it appears from the report that there is ongoing seasonal and long-term change throughout the coast. Coast residents see changes to beaches through the year.
With all the factors affecting the region, the agencies involved hope to maintain a healthy coastline by addressing any negative issues before they permanently damage this natural resource.
Thanks to National As-sessment of Shoreline Change: Historical Shoreline Change along the Pacific Northwest Coast, by Peter Ruggiero, Meredith G. Kratzmann, Emily A. Himmelstoss, David Reid, Jonathan Allan, and George Kaminsky.