Washington Coastal Landforms
The coastline of the state of Washington is 4,296 km long and consists of three segments: the eastern coast and islands from the Canadian border in the north down to the straits and islands of Puget Sound in the south, the northern coast of the Olympic Peninsula along the Strait of Juan de Fuca, and the outer, western, coast facing the Pacific Ocean. Along the eastern side of the Olympic Peninsula is the Hood Canal, a 104 km long inundated glacial trough. An account of the coastal features of Washington State was provided by Shepard and Wanless (1971) and a geomorphic classification of the ocean coast by Terich and Schwartz (1981).
Locations of places mentioned can be found in the Washington Atlas and Gazetteer published by the DeLorme Mapping Company, P.O. Box 298, Freeport, Maine 04032, USA http://www.delorme.com. Further topographic details are shown on the relevant 1:24,000 Washington 7.5 min maps produced by the United States Geological Survey, Denver, Colorado 80225, USA Reference can be made to the Washington State Department of Ecology collection of air oblique photographs of the coast at http://apps.ecy. wa.gov/shorephotos/.
The geology of the Washington State coast is dominated by the folded and faulted Tertiary formations of the Olympic Peninsula and the extensive Pleistocene glacial drift and associated deposits of the Puget Sound region, which extend northward across the Canadian border and also occupy valleys and mantle coastal slopes along the Pacific seaboard. There are Mesozoic and Palaeozoic formations south of Bellingham and in the San Juan Islands.
There was intensive Pleistocene glaciation, producing rugged mountains and wide mantles of glacial drift deposits in the lowlands. Shepard and Wanless (1971) commented that although Ozette Lake (12.8 km long and over 90 m deep) lies in a basin scoured by an ice sheet, the coast between Cape Flattery and Quillayute River shows little evidence of glaciation: there are no fiords. They suggested that the ice was relatively stagnant in the coastal fringe, where it melted to deposit a glacial drift mantle.
Cliffs and bluffs along much of the coast and around islands are cut into this glacial drift, and sand and gravel derived from these has produced beaches and spits, especially on the islands, along the eastern coast, and around Puget Sound. Bedrock outcrops, mainly of Mesozoic and Tertiary formations, are found on headlands and along shores where the glacial drift mantle has been removed by marine erosion, and are more prominent on the Pacific Ocean coast.
Stacks and natural arches along the Washington coast between the Quillayute River and Point Grenville are the outcome of differential erosion of Eocene (Quinault Formation) volcanic rocks, siltstones and sandstones and the Miocene Hoh Rock Assemblage, which consists of a basic mélange of chaotically mixed blocks of hard sandstone and basalt in a matrix of softer mudrocks and an overlying steeply tilted and overturned formation of sandstone, siltstone and conglomerate. Evidence that the Hoh mélange rose discordantly as diapirs or piercement structures through the overlying sedimentary beds can be seen in sea cliff exposures where the mélange is bounded on both sides by strata steeply dipping outward; and in offshore sub-bottom profiles indicating a doming of otherwise horizontal beds. Due to the easily eroded soft claystone and broken siltstone within it, the Hoh mélange forms embayments along the coast between headlands of the more resistant sedimentary beds of the upper Hoh Rock Assemblage and the Quinalt Formation. Some large blocks of mélange hard sandstone and basalt still remain as erosional remnants in stacks offshore.
The coastal climate is cool temperate and humid, with extensive winter snow in the mountains. The Pacific Coast region has an average annual rainfall of about 2,000 mm increasing to 2,875 mm in the rain forest area inland of La Push. Along the forested coastal strip the principal trees are Western hemlock (Tsuga heterophylla), western arborvitae (Thuja plicata), Douglas fir (Pseudotsuga menziesii), Sitka spruce (Picea sitchensis), and Lodgepole pine (Pinus contorta). Westerly winds prevail, but easterlies are frequent, particularly in winter. On the Pacific coast onshore winds are highly variable, between SSW and NNW. East of the Olympic Mountains rainfall is reduced in a rain shadow region, the Sequim district being well known for its dry climate (annual rainfall down to about 400 mm), but the eastern coast is also relatively wet (1,000–1,200 mm).
Tides are typically mesotidal, from about 2 m at neaps to 4 m at springs. Mean spring tide ranges on the eastern coast at Bellingham and Anacortes are 2.2 m, at Seattle 3.1 m and rising to 4.0 m at Olympic in Puget Sound, but on the Strait of Juan de Fuca they diminish to 1.8 m at Port Angeles, and on the Pacific Ocean coast are 2.2 m at Cape Flattery and 2.1 m at Willapa Bay. Nevertheless, tidal currents can be strong through narrow straits, as in Deception Pass, between Fidalgo Island and Whidbey Island, where they attain 18.5 km/h (10 knots), while currents of about 3–7 km/h (1.6–3.8 knots) are measured off Cape Flattery.
Wave action along the eastern coast and in Puget Sound is determined by local winds across often short fetches in straits and between islands, but on the Pacific coast westerly ocean swell accompanies locally generated and occasional storm waves. Net longshore drifting varies with configuration (Schwartz et al. 1985): Sandy Point, north of Bellingham, has grown southward but Ediz Hook and Dungeness Spit on the Strait of Juan de Fuca have grown eastward as the result of north-westerly wave action, and the latter has also been shaped by waves from the east and north east. On the Pacific coast the prevailing south-westerly waves generate net longshore drifting northward, as can be seen in the development in that direction of the Long Beach Peninsula and the northerly deflection of the mouths of such rivers as the Copalis, Moclips, Quinault, Queets, and Hoh. There are occasional local reversals, as at La Push, where wave refraction around two large stacks has caused a spit at the mouth of the Quillayute River to grow towards the south.
Occasionally tsunamis generated by tectonic disturbances along the nearby plate boundary have produced giant waves on the Pacific coast. There is stratigraphic evidence of rhythmic estuarine deposits along the shores of Willapa Bay and Grays Harbour, interpreted as indicating up to six major earthquakes (magnitude 8 or 9) along this zone in the last 3,500 years, with an average return period of 500–540 years (Atwater and Hemphill 1997). At Willapa Bay serial exposures of buried forest and marsh soils, with the uppermost soil mantled by tsunami- deposited sand, date the most recent tsunami event as occurring in 1700 (Atwater 1996). Corroborating this event are historical records in Japan of a devastating tsunami reaching the coast there on January 26, 1700 (Atwater et al. 2005). This predates European settlement of the Washington coastal area, but in the 1800s coastal native people described nearby Neah Bay as being flooded in the “not very remote past without any swell”, while canoes were lifted into trees and many people were drowned.
The Washington coast has been subject to changing land and sea levels, with tectonic uplift in the Olympic peninsula and along the Pacific coast associated with movements on the nearby subducting Juan de Fuca Plate (Atwater 1996) and Quaternary isostatic movements related to land depression by glacial ice loads and recovery and after deglaciations as well as oscillations of sea level. In consequence there are terraces at various levels in the coastal region, active emergence along the shores of Juan de Fuca Strait and the eastern coast and islands, and active submergence south of Cape Flattery and in the southern part of Puget Sound.
Cliffs have been cut into glacial drift and bedrock formations on coastal sectors exposed to strong wave action, especially on the Pacific coast, where there are also forested bluffs, usually with some basal cliffing, and these show occasional recession by slumping and landslides, especially during storms and periods of heavy rainfall. The Pacific coast of the Olympic Peninsula is one of the great scenic coasts of the world. Differential erosion of Tertiary continental and marine sediment and volcanics has produced sea caves, stacks, arches and high cliffs. Long term coastline recession is indicated by numerous stacks and islands in coastal waters (mostly within 2 km of the shore), and it is possible that episodes of substantial cliff recession have taken place during occasional tsunamis.
Many of the stacks and small islands off the coast south from Cape Flattery are residuals of harder rock, including Eocene volcanics, sandstone and siltstone, the Miocene Hoh Rock Assemblage and the Pliocene Quinault Formation. These are found sporadically within a softer sandstone and mudstone matrix in mélange formations outcropping along the coast, and are exposed and left standing offshore as the softer rocks are removed by marine erosion. Bluffs cut in glacial drift on the islands and along the eastern coast also recede as the result of recurrent local landslides.
Shore platforms are not as well developed on the coast of Washington State as on other Pacific coasts (see Australia, New Zealand, Japan), but they are found on the Cape Flattery peninsula (Bird and Schwartz 2000). They include subhorizontal high tide benches produced largely by weathering processes and seaward sloping intertidalsubtidal shore platforms cut by abrasion where waves move sand and rock fragments to and fro. Where sediment accumulations exist along the inner edges of shore platforms, they consist mostly of coarse gravel and cobbles; sandy beaches are to be found only in the occasional embayments along this stretch. Similar features are seen on some headlands along the Pacific coast and the Strait of Juan de Fuca, but shore platforms are poorly developed on the eastern coast and around the islands.
On the eastern coast and island shores there are sand and gravel beaches, often with cobbles and boulders, derived from glacial drift cliffs and the sea floor. On the shores of the Strait of Juan de Fuca and along the Pacific coast sand and gravel is also supplied by rivers, and heavy driftwood concentrations are found along the shore.
As on other coasts dominated by glacial drift deposits (Denmark, for example) there are numerous spits, some straight, some recurved and some cuspate. Dungeness Spit and Ediz Hook, respectively 8 and 5.6 km long, are two large spits on the southern side of the Strait of Juan de Fuca. Damming of a river and barricading the foot of a cliff, both west and updrift of Ediz Hook has caused considerable erosion at the base of this highly industrialised spit. The U.S. Army Corps of Engineers has recently initiated a maintenance program consisting of foreshore revetment and periodic beach nourishment. Smaller spits have formed on island and peninsula shores, particularly at points where the coastline changes direction (Finlayson 2006).
On Cape Flattery beaches are confined to coves, but southward along the Pacific coast there are long sand and gravel beaches between rocky headlands. South of Moclips the coast consists of broad, prograded sandy beaches fronting dunes. Provenance of the accreted sand along this sector has been attributed to the Columbia River to the south, whence sand has been carried northward by longshore drifting. With the construction of large dams on the Columbia during the twentieth century, it is speculated that the progradation regime may have ceased and possibly will turn to one of erosion. The beach that prograded alongside the breakwater built on the northern side of the Columbia River mouth at Cape Disappointment is now eroding, and erosion has followed earlier progradation alongside breakwaters at Point Brown and Westport, north and south of the entrance to Grays Harbour.
Coastal dunes are best developed on the Long Beach Peninsula, where there are multiple rows of beach and dune ridges, each of which was built parallel to the prograding sandy coastline. Locally there are blowouts and small transgressive dunes, as on Leadbetter Point at the northern end of North Beach Peninsula, but the extensive dune fields of the Oregon coast have not developed here. Similar dune morphology has developed along the coast south of Copalis Beach to Ocean Shores and Point Brown, and between Westport and Cape Shoalwater. Otherwise there are only minor dunes, chiefly behind beaches near the mouths of rivers and on some of the spits in northern Washington. One small dune at Fort Worden State Park, near Port Townsend, has been planted with dune grass to maintain it in an intensively used area.
The southern part of the Pacific coast is backed by a gently rolling plain, with two large estuarine lagoons, Willapa Bay and Grays Harbour, developed by the submergence of the mouths of valleys cut by rivers during phases of lower sea level, followed by the growth of barrier spits on the ocean shore, constricting their entrances. Northward migration of the main Willapa Bay inlet channel is believed to be the cause of severe beach erosion on the northern shore, at Cape Shoalwater, where the coastline has receded up to 3.7 km over a 76 year period. Reference has been made to the breakwaters built to stabilise the entrance to Grays Harbour.
There are small estuaries at the mouths of rivers on the Pacific coast, notably the Quillayute and Queets, and the Pysht River on the Strait of Juan de Fuca, and the growth of the compound Dungeness Spit has almost enclosed the waters of Dungeness Bay as a coastal lagoon. Crockett Lake on Whidbey Island is an example of a coastal lagoon enclosed by a wave-built barrier of sand and gravel.
Several deltas have been built on the eastern coast where rivers have deposited large loads of sediment brought down from mountainous catchments. They include the deltas of the Lummi and Nooksack, the Samish, Skagit and Stillaguamish deltas, the Snohomish delta near Everett, the much modified Puyallup delta (largely converted to Tacoma docks) and the Nisqually delta at the southern end of Puget Sound. The Skohomish River has built a marshy delta at the Great Bend on Hood Canal. On the Strait of Juan de Fuca coast the Elwha delta is prominent.
Marshes and swamps (sloughs) have formed on the more sheltered parts of estuary and lagoon shores, and in straits and bays protected from strong wave action by peninsulas, islands or spits. There are corridors of fresh water swamp between the north-south dune ridges on Long Beach Peninsula, some of which are used to cultivate cranberries.
The Coast of Washington from North to South
Point Roberts is a rectangular peninsula, an isolated segment of the United States, cut off because the Canadian boundary, the 49th parallel of latitude, runs westward across Boundary Bay to intersect it between Maple Beach and Boundary Bluff. It has beaches of sand and gravel bordered by multiple sand bars.
Drayton Harbour is a NW-facing horseshoe-shaped bay bordered on the western side by steep wooded bluffs, and partly enclosed as a lagoon by the long Semiahmoo spit that has grown north-east toward Tongue Point opposite the harbour structure at the town of Blaine.
This spit shelters salt marshes and mudflats exposed at low tide in Drayton Harbour on its landward (eastern) side, while the more exposed western shore consists of a beach of well-rounded pebbles and sand that continues southward below wooded bluffs and cliffs 20–25 m high, with occasional landslides in grey clayey sand (glacial drift). At the southern end of Semiahmoo spit, adjacent to the bluff and beside a sewage treatment site, is a large Indian midden over 6 m thick, dating from 4,000 bp onwards and rather overgrown. The beach passes in front of slumping bluffs south towards Birch Point (Fig. 1.2.1).
Birch Bay is similar in outline to Drayton Harbour, but faces SW and has no enclosing spits. Mean spring tide range is about 3.6 m, and at low tide extensive sand bars are exposed in front of a gravel beach segmented by groynes. The beach outline is an asymmetrical (log-spiral) curve, produced by the refraction of waves from the NW, and although there are episodes of northward and southward drifting net longshore drift is zero. A succession of emerged coastlines in the hinterland of Birch Bay, marked by a stairway of glacial rebound terraces, follows the same asymmetrical curve.
South of Neptune Beach is Sandy Point, a large spit that has grown southward as the result of wave action sweeping sand and gravel along the coast (Fig. 1.2.2). In the 1960s canals were dredged within the spit to form a marina, and there are now many houses behind the beach and around the boat channels. Unfortunately, beach erosion has become a serious problem, and residents have built sea walls and boulder ramparts on the shore to protect their properties. The spit is low-lying, and occasionally overwashed and flooded during storms. In the 1920s it was temporarily breached, and the storm of Easter 1977 swept sand and gravel in from the beach and damaged several houses. Within Lummi Bay, to the south, are the eroded (and now embanked) remains of the Lummi delta, which decayed after the diversion of the Nooksack River eastward into Bellingham Bay in 1877 (see below).
Portage Point is at the south-eastern end of the Lummi Nation Indian Reservation peninsula. The Portage (Fig. 1.2.3) is a tidal divide (intertidal tombolo) where a road is exposed at low tide, giving access to Portage Island. Brant Point is a sandy spit with shoals curving out in the lee of Portage Island into Bellingham Bay. There is a cliff cut in glacial drift on the southern end of Portage Island at Point Frances (Fig. 1.2.4) which is typical of the intermittently active cliffs in this region.
On the northern side of Bellingham Bay the Nooksack River has a growing delta, and the bay water is discoloured by brown silt and clay when the river floods. The Nooksack River has a northern branch, Lummi River, which flows to the sea in Lummi Bay on the northern side of the peninsula. In the mid-nineteenth century the Nooksack had become choked with a massive log jam just below the divergence of the two rivers, and some of the water and sediment discharge was carried down Lummi River into Lummi Bay. In 1876–1877 the log jam was removed, and the Lummi River diked off. After that the Nooksack delta began to grow out into Bellingham Bay (Shepard and Wanless 1971).
The San Juan Islands are scattered, mainly forested islands of various sizes and shapes in the southern part of the Strait of Georgia. They represent the partial marine submergence of a mountain range, dissected by glaciated valleys that are now fiords. San Juan Island is the largest of the group, about 29 km long with an average width of 10 km, a hilly island rising to the grassy granite slopes of Mount Young, 198 m high. It has steep coasts and rocky shores, declining to a narrow peninsula in the south-east, extending to Cattle Point. On the southern coast False Bay is a shallow rounded embayment with a wide intertidal zone.
To the north of San Juan Island is Waldron Island, consisting of a south-eastern upland of Upper Cretaceous shaly sandstones and conglomerate culminating southward in the steep-sided narrow Point Disney, which has vertical cliffs up to 150 m high on its western flank. On the eastern coast is rocky Mail Bay, and to the north a lowland of glacial drift rising to 30 m above sea level. Stratified glacial deposits outcrop in 30 m cliffs near Point Hammond at the north-eastern end of the island, and there are several small promontories of exposed bedrock, the most prominent at Fishery Point in the north-west. From here North Bay curves out to a sharp cuspate point of glacial drift projecting westward to Sandy Point. To the south Cowlitz Bay is another curved bay that extends south to Point Disney, and near the south-eastern end is intertidal Mouatt Reef, rising a metre above low tide.
To the north of San Juan Island is Spieden Island, a narrow ridge rising to 116 m. Nearby is Flattop Island, which has a steep rocky north-west coast and a surface that is not flat, but slopes south-east with the dip of the rock formations. Gull Rock, off the north-west point of the island, is split by a chasm cut out of shale between hard conglomerates. The hard rocks form reefs, notably White Rocks, one of which rises 10 m above high tide level. To the west is Stuart Island, almost split by elongated Reid Harbour, with Turn Point at its western end looking across Haro Strait to the similar Canadian islands that border Vancouver Island.
Also to the north of Waldron Island is Bare Island, a small island and seabird colony rising 12 m above sea level and almost unvegetated. Narrow inlets have been cut in steeply dipping shales on the east and west coasts, and there is a cap of glacial drift as well as much guano.
Orcas Island is M-shaped, with a smooth north- eastern coast following the geological strike and to the south steep- sided ridges separated by deep inlets, East Sound, West Sound and Deer Harbour. Mount Constitution, the highest peak in the San Juan Islands, rises to 759 m. Point Doughty is low and narrow, projecting into President Channel, and Freeman Island is a small island to the south that has a broad flat rock platform exposed at low tide. There are broad flat rocky reefs off the north coast, including Parker Reef, exposed at low tide. Lopez Island is a lowlying island to the south of Orcas Island.
On the mainland coast Bellingham Bay is a broad bay opening southward and bordered by steep bluffs and occasional cliffs. Relics of the wooden supports for the Bellingham and British Columbia Railroad stand offshore along the SE coast, and at Bellingham the Georgia Pacific water treatment lagoon is prominent on the shore. Aerating sprinklers and introduced bacteria and fungi were used to break down chemicals generated by the paper works and discharged into the sea, but this reduction of pollution in Bellingham Bay resulted in the return of the shipworm Teredo, which bored into the wooden pilings that support piers and attacked the rafts of logs that used to be floated in by sea.
Fairhaven is a historic neighborhood, dating from the mid-nineteenth century. The coast has been modified by reclamation. Towards the end of the nineteenth century large quantities of sand and gravel were sluiced from Poe’s (Post) Hill Point, which was an 18 m high promontory, and deposited in the bay to form new land that was then called Commercial Point for the development of shipbuilding yards, boat piers and factories. Depletion of the beach at Marine Park, Fairhaven, was countered in 2004 by emplacing an artificial beach of shingle.
South of Fairhaven Chuckanut Mountain (Fig. 1.2.5) descends to a steep forested coast on Cretaceous sandstones, passing southward across the Oyster Creek Fault to Palaeozoic metasediments. Below the steep slopes mudflats are exposed at low tide on the shores of Samish Bay. The view south from Chuckanut Mountain is of a wide coastal plain which includes the Samish River delta (Fig. 1.2.6). Samish Island, a wooded flat-topped ridge (two former islands linked by a sandy tombolo), was attached to the mainland by reclamation of intertidal land between earthen dikes by Dutchmen more than a century ago.
Offshore is a group of islands including high Cypress Island and low-lying Guemes Island. Sand and gravel eroded from cliffs has supplied beaches and spits shaped by wave action on the shore of Lopez Island (Fig. 1.2.7).
South of the Guemes Channel is Fidalgo Island, the inner part of which is separated from the mainland only by a marshy isthmus followed by the Swinomish Channel. Shannon Point is a cliffed promontory at the north-western end with glacial drift (Vashon drift) of the Fraser glaciation) over strongly folded and metamorphosed Mesozoic sediment and volcanics and a crystalline basement of Devonian rocks. Fidalgo Head on the west coast is a grassy bluff with outcrops of serpentine rock, above the swirling waters of Burrows Channel, looking across to the San Juan Islands. To the south is Deception Pass (Fig. 1.2.8).
Deception Pass is located between Fidalgo Island and Whidbey Island and is a deep and narrow strait through which the tides swirl at up to 18.5 km/h (10 knots). It is bordered by steep rocky cliffs. When it was discovered by Vancouver in 1792 he thought it would lead through to a harbour, but when he found otherwise he named it from having been deceived. West Point (Fig. 1.2.9) has been truncated by strong tidal currents.
Whidbey Island is about 145 km long, parallel to the mainland coast and extending southward to Seattle. On the west coast high cliffs of sandy glacial drift face the Strait of Juan de Fuca, with beaches and a looped barrier (Fig. 1.2.10). Point Partridge and Admiralty Head are prominent headlands, and on the latter is Fort Casey, where an old searchlight tramway protrudes 4 m from the cliff below an artillery fort, indicating recent recession of the cliff. This part of Whidbey Island has the Weird Pits, which are kettle holes up to 30 m deep which formed as the result of collapse following the melting of chunks of ice left in the glacial drift after the glaciers receded. Near Point Partridge one of these has been excavated by the sea to form a cove with a little lagoon.
On the east coast of Whidbey Island a succession of promontories separates coves and harbour bays. Bluffs with a scrub or forest cover alternate with cliffs exposing glacial drift deposits, and there is occasional slumping in the bluffs. At low tide a gravelly foreshore is exposed at the village of Coupeville, founded in 1852 on slopes descending into Penn Cove. Skagit River has built a delta on which the river splits into North Fork and South Fork, on either side of Fir Island, and there are relics of many distributary channels.
Camano Island, parallel to Whidbey Island east of Saratoga Passage, has wooded bluffs and occasional cliffs. Camano Head (100 m) is one of the tallest, steeply sloping bluffs in the archipelago, with tanglewood scrub sliding down the slope.
South of Stanwood the Stillaguamish River has built a delta into Port Susan, a bay sheltered from westerly winds and waves by bluffs in the lee of Camano Island. The coast southward along the Tulalip Indian Reservation has wooded bluffs and sand and gravel beaches, with some minor spits. Mission Point is a hooked sand spit sheltering Tulalip Bay.
A delta has been built where the Snohomish River and Steamboat Slough curve out on either side of Smith Island, north of the town of Everett. This town is built on low hills beside the valley of the Snohomish River. The waterfront harbour on the shores of Port Gardner Bay is sheltered by a chain of low islands extending north to Jetty Island, partly artificially formed by the dumping of spoil from dredging. Reclamation of the Everett waterfront has formed a series of docks and marinas and a large U.S. naval station at the southern end.
Puget Sound was cut by glaciers and meltwaters which formed deep, steep-sided channels, into which the sea flooded to form marine inlets that wind and branch deep into the state of Washington; inlets bordered by forested bluffs. The islands are generally steep-sided and flat or gently undulating, possibly as the result of marine planation of the glacial drift deposits at higher sea levels. The rise and fall of the tides in Puget Sound is about 2.1 m in the north, increasing to nearly 3 m in the south, and at low tide sandy and gravelly beaches and muddy fringes are exposed.
Spits are found on many of the islands (Fig. 1.2.11), and there are intertidal and subtidal shoals.
South from Everett bluffs and cliffs form the eastern coast of Possession Sound, and extend past Mukilteo to Norma Beach, where the coastal suburbs of Seattle begin. Bluffs and small headlands with some coves and beaches line the Seattle coast. Seattle has spread across the isthmus of ridges and valleys that trend south to north on the eastern side of Puget Sound, has a coastline of wooded bluffs with headlands and bays, and some of which have been reclaimed for port development.
West Point is a cuspate spit that carries a City of Seattle sewage treatment plant, a small Metro lighthouse marking the northern point of Elliot Bay, and a Coast Guard building.
Elliot Bay provided a good harbour in deep water, below a steep wooded hillside with ravines and springs. This part of the coast has been much modified by land reclamation; in 1902–1930 Denny Hill was removed and the earth and rock sluiced from it was dumped to reclaim former tideflats in Elliot Bay.
Tacoma is a large city on a wide plateau near the southern end of Puget Sound. Commencement Bay is broad, with the delta of Puyallop River at its head, modified to form Tacoma docks. The coast southward is dominated by steep bluffs cut in glacial drift, extending past the narrow promontory at Point Defiance.
Towards the southern end of Puget Sound the Nisqually River has built a shrubby deltaic plain with extensive marshes. The head of Budd Inlet, to the west, has been enclosed to form Capitol Lake, alongside Olympia.
Bainbridge Island, on the western side of Puget Sound opposite Seattle, is a broad plateau of glacial drift bordered by bluffs, separated from the mainland by Agate Passage. Restoration Point has an emerged shore platform 6 m above the modern one, probably uplifted tectonically. Point Monroe has a looped sand barrier enclosing a lagoon at the northern end of Bainbridge Island. To the south is Vashon Island, similar to Bainbridge Island, attached to Maury Island by way of an isthmus at Portage.
On the west coast of Puget Sound opposite the cliffy southern end of Whidbey Island is Point No Point, a rounded or lobate spit like many others on Puget Sound, shaped by waves delivering sand and gravel but blunted by strong tidal currents.
Hood Canal, the long channel that diverges from Admiralty Inlet near Port Ludlow is generally 3–5 km wide as it runs southward past Hoodsport to the Great Bend, and 1.5–3 km wide as it swings north-east to its marshy head at Lynch Cove, near Belfair; it is bordered by steep wooded slopes that are sometimes disrupted by landslides, the scars of which persist for some years. Inflowing streams have built small deltas, such as that of the Dosewallips River, and a large delta has been built by the Skokomish River south of the Great Bend near Union. Longbranch Peninsula, between Case Inlet and Carr Inlet, has springs flowing from cliffs of gravel and clay on its west coast.
The Hood Canal opens northward into Admiralty Inlet near Port Ludlow, sited on a slight hill overlooking a harbour. To the north, Marrowstone Island and Indian Island are islands of glacial drift that run north-south. They are fringed by bluffs and minor cliffs, and have beaches of sand and gravel and spits, such as the cuspate spit at Marrowstone Point.
Port Townsend on the east coast of the Quimper Peninsula, looks across Admiralty Inlet to Whidbey Island, and has bluffs fronted by a reclaimed shore area (Zelo et al. 2000). Beach sand drifts northward past Fort Worden.
Point Wilson at the northern end of Quimper Peninsula, on the western side of the entrance to Admiralty Inlet and Puget Sound, is a sand and gravel spit with low dunes. It has been shaped by waves arriving from the south-east, across Admiralty Inlet, and from the west, along the Strait of Juan de Fuca.
The Quimper Peninsula, bordered to the west by Discovery Bay is broad and flat-topped with steep forested bluffs. At Fairmont, a village at the head of Discovery Bay, salt marshes and mudflats are exposed as the tide falls. Offshore is Protection Island, which became a national wildlife refuge in 1982.
West of Discovery Bay is the broad Miller Peninsula, and then Sequim Bay, which is essentially a lagoon almost enclosed by Gibson Spit (Fig. 1.2.12) which has grown southward on the western side and Travis spit, which has grown eastward. Strong tidal currents flow through the gap.
Dungeness Spit (Fig. 1.2.13) is a sand and gravel spit nearly 10 km long, a long narrow ridge of sand and gravel, piled with driftwood, with lobes of washed-over sand, runs out eastward to the distant lighthouse (Schwartz et al. 1987). Sediment from eroding cliffs in glacial drift to the west has drifted alongshore to build the spit, which is still growing eastward. It is backed by a lagoon, Dungeness Bay, containing truncated Cline spit and broader Graveyard Spit, running sharply back from the middle of Dungeness Spit, and intervening marshes and lagoons (Fig. 1.2.14).
Dungeness Spit has been supplied with sand and gravel from eroding cliffs in glacial drift to the west. The steep cliffs cut in sand and gravel between Dungeness Spit and Port Angeles are receding, and pose a problem for houses built on cliff-top land. Cliff recession occurs as the result of basal wave attack, but there is also slumping, particularly after wet weather when the glacial drift deposits become overloaded with groundwater and are unstable. Port Angeles stands in the lee of the Ediz Hook spit.
Ediz Hook is a spit 5.6 km long that has grown out from the coast east of the Elwha delta, supplied with sand and gravel from eroding cliffs and from the Elwha River. In recent years erosion has become severe along the shores of this spit, partly because of the reduction of sand and gravel supply from cliffs that have been stabilised and partly because of the damming of the Elwha River, so that the shore is now heavily armored with large rock boulders, which preserve the spit artificially as a breakwater for Port Angeles.
The Elwha River is incised in a deep valley. It has built a delta, but this is eroding because dams have intercepted most of the sediment previously brought down the river to the coast. West from the mouth of Elwha River the coast consists of bluffs and cliffs, interrupted at the mouths of many small river valleys. Pysht is at the mouth of two valleys, and to the west there is a rocky headland and a prominent sea stack to the west on Pillar Point.
Clallam Bay is a village with a small fishing harbour, where a walkway leads out from the coastguard station to a steep headland and Sekiu is a village on the western shore of Clallam Bay, with a sheltered harbour. To the west are cliffs fronted by shore platforms exposed at low tide. Seal Rocks, east of Neah Bay, include high Old Hat islands (Fig. 1.2.15), surrounded by subhorizontal high tide shore platforms produced largely by weathering processes (Bird and Schwartz 2000).
Neah Bay, to the east of Cape Flattery, has a harbour protected by a breakwater linked to Waadah Island, and has a crescent-shaped beach of pure white sand connecting Bahada Point.
Tatoosh Island (Fig. 1.2.16) is a flat-topped cliffedged island offshore, the northwesternmost point of the 48 coterminous United States at the western end of the Strait of Juan de Fuca.
Cape Flattery has massive sandstone cliffs with basal rock ledges, looking out to Tatoosh Island. The peninsula consists of Lower Tertiary (mainly Eocene) stratified sandstones and siltstones and, locally massive or conglomeratic. The cliffs show weathering features, including tafoni and caves, structural ledges, and basal subhorizontal high tide shore platforms (Bird and Schwartz 2000).
High cliffs run south from Cape Flattery towards Waatch Point, where there are wide rocky shore platforms cut by abrasion as waves move sand and gravel to and fro. Hobuck Beach at the mouth of Waatch River curves round Mukkaw Bay towards Anderson Point. Sooes River flows northward behind a barrier spit to a deflected outlet.
Anderson Point has subhorizontal high tide shore platforms around islands and rock stacks. Shishi Beach, 4.8 km of sandy shore, runs south from Portage Head in the Makah Indian Reservation; there are numerous grey jagged reefs and stacks offshore. Point of the Arches is a cliffy headland with caves and tunnels and many stacks offshore. Between Point of the Arches and Cape Alava is wilderness coast in the Olympic National Park, accessible only to walkers. Cape Alava is the most westerly point in the coterminous United States. South from Cape Alava, near Ozette, the coastline is a series of beaches a few hundred metres long with a headland at each end. The headlands are 30–50 m high, steep and thick with salal bush, and impassable at high tide.
Alava Island stands as a mesa in the ocean, first and biggest of a group of sea stacks, reefs, isles and boulders known as The Flattery Rocks. One of the first headlands south of Cape Alava is Wedding Rock, a dark-basalt cliff with broken rocks at its base. These rocks have served as a canvas for ancient artists, with petroglyphs carved on the rocks. Sand Point, down a 15 km walking trail from Ozette, is notable for its shore pools exposed when the tide is out. Ozette Lake is elongated parallel to the coastline, and one report suggests that it was impounded by a bouldery glacial moraine on its western shore (Alt and Hyndman 1984). Its great depth (90 m) indicates that it occupies an ice-scoured depression. The coast continues southward past Point Johnson and several other rocky promontories. Hole in the Wall is on a small headland penetrated by a wave-cut cave. There are many outlying sea stacks of dark basalt. Rialto Beach, a curving bank of pebbles and cobbles backed by heaps of driftwood worn smooth and clean by the abrasive waves, runs out from the mouth of Quillayute River at La Push. The harbour is protected by a large breakwater, strewn with driftwood, linked to one of several forested flat-topped islands.
To the south are First, Second and Third Beaches, extending down to rugged Teahwhit Head. 27 km of steep forested wilderness coast extends between La Push and Ruby Beach, which takes its name from the polished black stones that can be found on the shore. This part of the coast is accessible only on foot, along Olympic National Park trails that run behind prominent Hoh Head and a succession of rocky capes and curving bays, with many islands and stacks offshore (Fig. 1.2.17).
Destruction Island is a bold, steep-sided island, 1.5 km long and 5 km offshore (Shepard and Wanless 1971), one of the very many islands and stacks off the oceanic Washington coast. To the south Kalaloch Creek swirls out past a slumping meander cliff to the sea. Southward the coastline straightens, and is fringed by a beach of sand and gravel. At Queets the beaches are again numbered rather than named: First Beach, Second Beach and Third Beach. Tunnel Island is penetrated by a large cave. There have been recurrent tsunamis on this coast.
Cape Elizabeth is a flat-topped promontory with cliffs cut in soft stratified siltstone and conglomerate (Quinault Formation) which run southward to the mouth of Quinault River. A 1902 photograph shows that a double arch in Eocene sandstone and conglomerate existed here, but before 1970 the inner arch collapsed. South of Taholah is Point Grenville, a rocky promontory of marine volcanic rocks, rising abruptly from the ocean, into which it extends a short distance in a semicircular shape. Outlying to the southeast are two pyramidal rocks 20–25 m high.
Moclips is a village on top of bluffs with pine and cedar forest at the mouth of Moclips River. The straight coast continues, with bluffs and cliffs rising behind a long sandy beach. Roosevelt Beach is a firm sandy surf beach in front of cliffs of soft dark sand. The barrier beaches continue southward to the mouth of the Columbia River. Roosevelt Beach narrows southwards past Copalis River to Copalis Beach, where the steep wooded bluffs, locally slumping, give place to dunes behind a narrow shingle beach with much driftwood.
At Sampson the beach and dunes become a barrier spit on the northern side of Grays Harbour. On it are extensive seaside resorts, including Ocean Shores. Grays Harbour is a large estuarine lagoon which narrows eastward to the mouth of Chehalis River, where Aberdeen and Hoquiam are log-shipping and lumber-milling towns. At Point Brown, on the northern shore, North Jetty was built to stabilise the entrance. A wide sandy beach, backed by dunes, built up after the jetty was first built, but is now eroding away, and at Ocean Shores a large condominium block which was threatened by shore erosion and protected by massive boulder rampart now projects on to the beach.
Westport on the broad sandy spit that borders the southern part of Grays Harbour stands behind the sand dunes, with long jetties built early in the twentieth century to stabilise the entrance to Grays Harbour and disperse the sand shoals that impeded navigation: at first the jetties led to widening of the sandy beach on either side of the entrance, but in the last few years there has been rapid erosion on the southern shore, and the Corps of Engineers has had to deposit about 600,000 cubic metres of sand and pebbles to make a wide isthmus that prevents the sea breaking through into Half Moon Bay and threatening Westport town.
Cape Shoalwater is a low promontory on the northern side of the entrance to Willapa Bay, and has been subject to severe marine erosion. Comparison of historical maps shows that Cape Shoalwater was been cut back 3.7 km over a 76 year period, and that since 1967 it has been receding about 30 m/year. Since the early charts were made the entrance to Willapa Bay has widened, and the erosion is partly due to the deep-water channel impinging on the Cape Shoalwater shore (Fig. 1.2.18).
Willapa Bay, once known as Shoalwater Bay, is a large coastal lagoon with a wide shoaly entrance, an irregular outline, rocky headlands and marshy coves, and the high forested Long Island; the average tide rises and falls about 2 m. It has been calculated that Willapa Bay exchanges 12 million gallons of water per tide: on the west coast only the Columbia River, San Francisco Bay, and Puget Sound exchange more than this.
Long Beach Peninsula is a barrier spit, consisting of sand brought down to the sea by the Columbia River, which has accumulated on the coast north of the river mouth. A wide beach is backed by grassy and forested parallel dune ridges, with Willapa Bay on the landward side, the dunes running from south to north, and separated by elongated hollows containing lakes and bogs.
Long Beach extends north from Cape Disappointment to Leadbetter Point at the entrance to Willapa Bay. South of Seaview the dunes come to an end, interrupted by cliffy North Head and the rocky Cape Disappointment promontory.
From Cape Disappointment there is a view of the long North Jetty, with much driftwood on the sandy beach that has grown very wide on its northern side. The breakwater was built to stabilise the northern side of the mouth of the Columbia River, and comparison of early maps and charts with the modern configuration indicates that a wide beach has formed on its northern side. Nearby is a deep, steepsided rocky inlet.
Large quantities of sand were carried down the Columbia River and swept into the sea in times of flood, and ocean waves have carried this onshore to build the beaches and dunes of North Beach to the north (and Clatsop Plains, in Oregon to the south). In recent decades the sand supply has diminished, possibly because of dam construction upstream, and beaches that were formerly built up with sand washed in from the sea floor now show signs of erosion. The explosive eruption of Mount St. Helens in 1980 sent large quantities of sediment down the Toutle River into the Cowlitz River and so into the Columbia River at Longville. The sediment reaching the Columbia River was largely fine-grained (silt and clay) rather than sand. At Longville the river shallowed overnight from, and dredging was necessary to 12 to 4 m restore navigability. Turbid water flowed downstream to the mouth of the Columbia River, but there was no sand accretion as a result of the Mount St. Helens eruption.
Along the northern side of the Columbia River steep slopes descend to the estuary shore. There is a succession of bays and rounded promontories, and Grays River and a number of smaller streams flow into the Columbia estuary from the north. Upstream the estuary becomes shoaly, with marshy islands extending at intervals up to the Lewis and Clark bridge at Longview.
References
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