Peninsula Rocks & Roots: Geomorphology - Part 4: Alluvial landscape features - estuary entrances

<I>KATHLEEN SAYCE photo</I><BR>Washaway Beach in winter 2004. While sand is accumulating on the southwest to west beach, starting in the lower right corner, erosion continues on the south-facing beach near the new breakwater, which runs into the main channel above a drainage ditch. The truncated roads show where lots once existed that washed away. Tokeland is in the middle distance, and the Willapa Hills are beyond.

Basic Concept: In the past 150 years, the Willapa Entrance has changed dramatically. Charts and topographic maps of 150 years ago show a long spit arching down to the southeast from Cape Shoalwater into the entrance, and the main channel near present day Leadbetter Point. Successive charts map the shift of the main channel northward over the next 150 years. During those decades, Cape Shoalwater disappeared into the surf and Leadbetter Point built up out of the surf and extended northward. This situation is not unique to this or any other coastline, and serves as a severe reminder of the fragility of coastal lands built of sand. Similar stories could be told for Grays Harbor and Columbia Entrances; see Komar for several such tales on the Oregon Coast.

No one who now lives remembers Leadbetter Point as it was 150 years ago. At that time, based on the first charts we have for this area, the Peninsula ended at what is now the north parking lot at the point, on the high dune. North beyond this dune were intertidal flats to the west of Grassy Island, which was mapped on the first charts. At high tide, this area was covered with surf. A channel ran between the island and the flats; access was not possible by land even on minus tides in those years.

By 1871, a long narrow spit of sand extended along the beach at Leadbetter Point towards Grassy Island. The spit slowly widened and built up, continuing to extend northward. Then, soon after the jetties were constructed at Columbia and Grays Harbor Entrances, sand flowed ashore in larger amounts and the beach and dunes built westward. Leadbetter Point built both north and west.

At the same time, Cape Shoalwater was eroding. Komar (1998, pages 114-115) illustrates the Willapa Entrance with charts from 1871-1891. Cape Shoalwater eroded from 1891 to 1967, as seen on historic charts and maps; continuing for another several decades, the cape's spit was basically gone by the late 1980s.

The entrance channel also shifted. In the last quarter of the 19th century, from south to north in the entrance were the flood channel (where water surged in on flood tides), the ebb channel (where it left on ebbing tides), and the long elegantly curved spit of Cape Shoalwater. By late in the 20th century this condition had reversed, so that one deep channel on the north end served to move water in and out of the bay, with minor channels full of water at flood tide.

Actually it was probably changing all the time, but by 1911 there were enough old charts to document the shift. As the main channel shifted north, it abandoned a succession of old paths, which filled in with sand and became minor channels.

This circumstance did not pass unnoticed, particularly by fishermen and coastal residents. Elders living from Grayland and Tokeland around to the Peninsula remember conditions from the 1930s onward, and talk of dunes, farms, other lands and landmarks that disappeared on the north side as the channel shifted. On the south side, they talk about the extension of the Leadbetter spit and annexation of Grassy Island.

In the 1930s the spit of Cape Shoalwater became the first unit of Willapa National Wildlife Refuge, set up to provide wintering habitat for Pacific Brant, which fed on eelgrasses behind the spit. But the spit was already rapidly eroding away. At the time of establishment, this unit of the refuge covered more than 1,500 acres. Now it no longer exists.

There were also hundreds of acres of intertidal shoals and dune fields south of Tokeland that disappeared as the main channel moved north. The last remains of Cape Shoalwater became known as Washaway Beach; ultimately dozens of homes were lost to the ocean - and continue to be lost to this day. In the 1990s, as the channel approached State Highway 105 southeast of Grayland, a short jetty was installed to stabilize the channel, protect the highway and stop erosion. You may judge for yourself how effective this action has been.

Meanwhile, on the south side of the Entrance, Leadbetter Point continues to build northward, and is now well north of Grassy Island, which some decades ago finally connected to land. The expansion on the south side is approaching 1,000 acres. The main channel of the 1850s-1870s has filled in, and a new spit sits on top of it.

The channel between the island and point disappeared in the 1960-1970s, then ceased to be tidal soon after. These days, Grassy Island can be reached at any stage of tide, as a dune connects it to a former end of Leadbetter Point. The present point is a few thousand feet to the north. The Willapa Entrance now appears to have three channels; the deepest one is on the north end, with two shallow channels to the middle and south.

Why did the channels shift north so dramatically, removing one spit and building another? Geologists speculate that the channel may have abruptly shifted to the south side in response to the last subduction zone earthquake in 1700. For a short period of time afterward, the main channel may have been just north of the high dune at Leadbetter Point, running between it and Grassy Island. Then as sand supplies and ocean long-shore currents re-stabilized with sealevel, it shifted northward. Euro-Americans arrived when it was about 150 years into that process. Now, 300 years later, we may be seeing the entrance at its north extension. Without a full 300 years of charts to substantiate this hypothesis, we can only speculate, and wait to see what happens after the next subduction zone earthquake.

Local Elements: Both sides of the Willapa Entrance can be seen from highways and refuges. Plan on using binoculars or a spotting telescope to make out some features. If you have the opportunity, fly over the entrance at low tide.

Local Examples: To see the north side of the entrance, drive west on Highway 105 past Tokeland to a series of short jetties, which jut out into the north channel about a mile from the ocean and Grayland. The deepest part of the channel is a few hundred feet offshore of this site. You can see entrance shoals and Leadbetter Point to the south, ocean shoals and a few water pipes, all that remains of several homes, to the southwest at low tide. Trees, roots and all, tumble off the edge of the dunes in this area, along with the remains of several buildings.

To view the entrance from land, drive on Highway 101 south of Bruceport Park to the viewing location just south of the park. From this site, with binoculars or a scope, you can see the shoals and channels on the other side of the bay at the entrance. During high surf at high tide, the channels stand out, with abundant surf spray on shallow ground and less surf over deeper water.

To see the entrance from Leadbetter Point, drive north on Highway 103 to Leadbetter State Park, and north to the north parking area, which is on the boundary between the park and wildlife refuge. Hike west to the ocean beach, then north several miles on the beach to the north tip. You can also hike around to Grassy Island, now southeast of the present tip. No signed trails go up the east side of the spit to Grassy Island, so if you cannot navigate or walk easily over rough ground, do not go up the bayside.

References, for more reading:

Komar, Paul. 1997. "The Pacific Northwest Coast: Living with the Shores of Oregon and Washington." Duke University Press, 195 p.

Pilkey Sr., Orrin H., Pilkey, Walter D., Pilkey, Jr., Orrin H. & Neal, William J. 1983. "Coastal Design: A guide for builders, planners, & homeowners." Van Nostrand Reinhold Co., Inc. 224 p.

Pilkey Sr., Orrin H., & Dixon, Katharine L. 1996. "The Corps and the Shore." Island Press. 272 p.

Terich, T. & Levenseller, T. 1986. "The severe erosion of Cape Shoalwater," Journal of Coastal Research, 2: 465-477.

Oregon Historical Society map set for the Lewis & Clark bicentennial - look at the 1851 chart of Willapa Entrance.

Kathleen Sayce is Shorebank resident scientist in Ilwaco. Her column explains the scientific underpinnings of our area. She has started with basic geology.

Internet search words:

Cape Shoalwater

Washaway Beach

And see articles over many years in Chinook Observer archives

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