The appearance of Oregon beaches changes with the seasons. Some of the most dramatic examples occur along our section of the coast. It’s a common phenomenon yet it invariably leads people to ask, “Where did the beach go?”
Indeed, if you visit the beach this time of year, it looks as if it’s been scoured clean of sand from the ocean waterline to the first row of sand dunes, also called a berm or foredune. Quite the contrast with the pillowy, loose sand of summer.
How does this happen? First,a few facts. According to the 1994 Scientific American reference book “The Evolving Coast” by Richard Davis, “sand” is not a thing, but a size. Smaller bits are “silt” and larger bits are “gravel.” The sand on Oregon’s beaches is primarily mineral sand, with most grains being a crystal or tiny chunk of rock eroded from Cascade Range and Coast Range sources.
The distinctly different seasonal beach profiles are attributed to the frequency and duration of energetic storms. During the winter, long-lasting storms with large breaking waves tend to sweep sand away and deposit it offshore in sandbars. By March, after four months of scouring by winter storm waves, most sandy beaches on the South Coast are flattened and seriously depleted of sand. Winter waves have carried most of the sand offshore to form extensive underwater sand bars. As winter storms become less frequent, these sand bars start to migrate back toward the beach, marching slowly across the sea floor like underwater sand dunes.
The process of sand bars moving ashore and rebuilding the beach continues sporadically throughout the spring and summer, but can be reversed any time, if late storms bring large, steep waves that sweep the sand back offshore.
Although the strong northwest winds of spring sometimes create wind waves that erode the beaches, these same winds also carry beach sand to the back of the beach, out of reach of all but the largest storm waves. In this way, the spring winds help build up dunes that may have been eroded by winter storms.
What are the origins of all this sand? Most is delivered by rivers that carry and collect sediment throughout their course and finally dump it in the ocean because the energy of river flow gets exhausted at this stage. The sediment load (mostly fine sand) is pushed back and forth towards the shore under the influence of rip currents, which flow at an angle to the shore and are spread along the shore by what’s called long shore current (Ocean current which flows parallel to the shore). In this way, new load of sands are delivered and spread by ocean currents, resulting in the creation of beach.
The scouring of the top layers of sand has another predictable yet interesting effect, and that’s to “unbury” shipwrecks. The most famous is the Sujameco, grounded at Horsfall Beach in the Oregon Dunes National Recreation Area north of Coos Bay
Constructed in 1920, the steamship Sujameco was a regular part of the lumber trade. On March 1, 1929, Captain JF Carlson was leading the Sujameco and its 35-man crew to Marshfield (as Coos Bay was called then) for the first time. Heavy fog hit. Carlson became confused, and later admitted he miscalculated his position.
Everything of value was eventually recovered and the wreck was salvaged several times, including during World War II for scrap metal. Since it sits so close to shore, it’s become a fun destination for visitors.
Yet not a trace is visible most of the year, so go soon if you want to see this season’s “show.”
Getting There
From North Bend and Coos Bay, head north on US 101, crossing McCullough Bridge. In just under 1 mile turn left (W) on TransPacific Parkway. Cross a causeway, small bridge and two sets of railroad tracks. Just past those, turn right (N) into the Horsfall Beach access road to the Oregon Dunes. Follow it to its terminus with the Pacific Ocean at Horsfall Beach. A $5 day use permit or seasonal pass is required.
(Shopper columnist Tom Baake is author of local guidebooks.)
