Tag Archives: Beach of the Month

Changing Beaches, Changing Uses, Mystery Structures: Rosy Mound Park, Lake Michigan, U.S.A; By William Neal, Peter Wampler & Brock Hesselsweet

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By William J. Neal and Peter J. Wampler, Department of Geology, Grand Valley State University, Allendale, MI, and Brock Hesselsweet, Hesselsweet Architects, Grand Haven, MI

One of the general rules of beaches is that ‘no beach stays the same,’ neither over long reaches or very short stretches nor for very long time intervals. This rule is as true for fresh-water beaches as those of the salty seas. Rosy Mound Natural Area about 2 km south of Grand Haven, Michigan, on the eastern shore of Lake Michigan is a good example (Figs. 1 and 2). Although a very small beach in terms of the Park’s lake frontage, the beach/dune complex tells a story of both geological change and human-induced changes.

Geologically, today’s Great Lakes are the product of over 12,000 years of post-glacial changes in the region, including numerous rises and falls in the ancestral Great Lakes. Ancient shorelines have been both landward and lakeward of where Rosy Mound is today, but the great parabolic dune that rises nearly 200 feet above lake level provides a sedimentary record extending back over 3000 years ago (Fig. 1). That was when the sand dune began to grow atop earlier lake sediments (Arbogast and Loope, 1999).

“The sand grains in these dunes are the survivors of earth history… ”
— W.Neal, P.Wampler & B. Hesselsweet

The bulk of the dune growth was probably over by a millennium ago, and by the time of European settlement the dune was covered by a mature beech-maple forest. The sand grains in these dunes are the survivors of earth history – the dominant quartz grains derived from Precambrian granites and gneisses of the Canadian Shield, worked and reworked, along with feldspars and garnets, magnetite, and a suite of less common minerals; from glacial grinding, to rivers, to sand bars, dunes, to beach, and back again to a dune that persisted for as long as 3000 years!

Large ancient parabolic dunes characterize much of the eastern shore of Lake Michigan, the most famous being those of the Sleeping Bear Dunes National Lakeshore (Neal and Wilson, 2014). These dunes are prehistoric in age and should be regarded as fossil dunes in that if damaged or destroyed, current natural processes will not rebuild them to their former state. The lakeside feet of such dunes have been eroded over time by waves, providing natural sand nourishment to the associated beaches. However, the last 150 years have seen major impacts on both the dunes and the beaches by human activities.

From Mining to County Park

European settlement brought change to the region and this specific area. The dunes were heavily timbered in the late 1800s and again in the early 1900s. The rise of the auto industry created a demand for foundry/casting sands, and the fossil dunes along the Lake Michigan shore were ideal in sand composition, a bulk resource, and economic to mine. By 1924 there was sand mining in the Rosy Mound area, and there are regional examples where entire dunes were mined away (Lake Michigan Federation, 1999). Rosy Mound was decapitated and scarred by mining, and opened to further erosion by wind (e.g., blowouts).

Beach and dune sand mining is a global concern (Coastal Care). The history of such mining along the Great Lakes is a story in itself, and by the 1970s the level of concern in Michigan led to state regulatory legislation which has been strengthened since the first Sand Dune Protection and Management Act (see Lake Michigan Federation, 1999, for summary).

Interest in preserving the Rosy Mounds tract began as early as the 1960s when students at Rosy Mound Elementary School petitioned a local senator for the state to protect the dune. By 1989 the Ottawa County Parks and Recreation Commission’s plan to acquire the Rosy Mound property, including 3,400 feet of beach front, was a number one priority (Michigan Trail Maps, 2016). The Standard Sand Company proved to be a good citizen to the community and cooperated in the land transaction with the State purchasing the land and then deeding it to the county. The park was dedicated in 2004, and the county has turned the area into a recreational, but protected environment.

Instructional nature trails through the forest and an extensive boardwalk system across the fragile dune habitat down to the beach replaced random foot paths that were contributing to erosion (Fig. 3). Areas were revegetated with plantings of native species, and the park is off-limits to dogs.

“The natural cycle of the fall and rise of Lake Michigan over time results in alternating times of wide beaches and transverse dune growth… ”
— W.Neal, P.Wampler & B. Hesselsweet

The natural cycle of the fall and rise of Lake Michigan over time results in alternating times of wide beaches and transverse dune growth, to times of narrow beaches and erosion of the back-beach dune (a vertical water-level span of 6 feet reflecting changes in annual precipitation and evaporation). Areas of private shoreline ownership are lined with houses, and significant numbers of buildings have been lost or damaged by storm waves and erosion. The typical response is for property owners to build shore-hardening structures (seawalls, revetments, groins), causing additional beach damage. The parks leave the beach in its natural state without man-made structures, so the subaerial beach recovers quickly when water levels fall.

After an extended period of high water levels from the 1970s into the 1990s, lake level fell from the late 1990s to 2014. Figure 3 gives a good indication of how wide the beach was in 2010 (note the position of the ends of the boardwalks in reference to the water’s edge and beach width in comparison to Figs. 4 and 5). The current rise has greatly narrowed the Park’s beach, and the erosional bluff in the dune is cut back to the ends of the boardwalks. One can expect this trend to continue, but nothing is threatened other than a minor stretch of the boardwalk. The dune that’s being eroded is less than 25 years old, and will rebuild on the next low water cycle. In the meantime, the locale provides a good example for students and land owners of how the beach/dune changes, particularly in response to lake/climate events.

Mystery Structures

Like all beach/dune complexes, a beach walk at Rosy Mound provides the opportunity to see sedimentary bed forms both on the beach and dune surface as well as in cross section where waves have scarped the beach or toe of the dune. Ripples, wave swash marks, dark placers of heavy-mineral sands (dominated by magnetite, garnets, amphiboles and a variety of other minerals), and current crescents around pebbles or other obstacles on the beach are common. But from time to time, after storms or strong wind events, some less common features are found, particularly in the eroded dunes and at the back of the beach. Two of these types of structures are highlighted here.

From time to time mysterious concretion-like structures are reported along the Lake Michigan shore (Fig. 6). Technically these are rhizocretions (Klappa, 1980), and they are found in association with driftwood or deadwood buried by dunes, and then re-exposed after the formation of cemented sand around the smaller limbs of the tree remains (Fig. 7). Here we note their occurrence at Rosy Mound, however, similar structures have been reported at other Lake Michigan shore localities as well as along Lake Superior. The latter were studied by Dietrich and Lampky (1981), and they found that the cementation of the sand was due to fungal mycelia. Their formation is the result of the fungus growing on buried, rotting wood in permeable sand. Wind and/or water erosion later exposes the concretion-like structures, usually in association with some of the remaining wood on which they formed (Fig. 8). At Rosy Mound two different concretionary forms were noted (Figs. 8 and 9).

“From time to time mysterious concretion-like structures are reported along the Lake Michigan shore. Technically these are rhizocretions… ”
— W.Neal, P.Wampler & B. Hesselsweet

A second unusual structure was found in these same areas of exhumed wood. These were mini-caverns with very small sand columns in the caverns (Figs. 10 and 11). The structures are somewhat like the mini-hoo-doo or toad-stool like forms that develop when beach sands dry out differentially, typically after storms cause water saturation, and then strong winds sculpt the sand layers (see for example: “Wind carves amazing formations in Lake Michigan sand,” Detroit Free Press).

However, the mini-cavern structures at Rosy Mound were in wind-blown sands that accumulated on a gentle slope. It appears the sand was water-saturated, and a very thin layer of fine sand was more cohesive than the underlying bed as the sand dried. This layer formed the roof of the mini-cavern (Fig. 10), while the wind etched the underlying sand away to form the columns. Some of the columns became detached at their bases as wind erosion continued (Fig. 11). As erosion continued, similar structures were nearly completely erased, leaving only odd hanging tongues of sand that would be difficult to explain if one had not seen the mini-cavern stage of formation.

Thanks to the foresight of children, State and County Officials, and a cooperative mining company, Rosy Mound Natural Park will serve the public for generations to come without additional compromise to the environment.


References

  • Arbogast, A.F. and Loope, W.L., 1999, Maximum-Limiting Ages of Lake Michigan Coastal Dunes: Their Correlation with Holocene Lake Level History: Journal of Great Lakes Research, 25(2), 372-382.
  • Coastal Care: Sand Mining
  • Dietrich, R.V. and Lampky, J.R., 1981, Fungus-Bound Quasi-Sandstone: Journal of Sedimentary Petrology, 51(4), 1133-1136.
  • Klappa, C.F., 1980, Rhizoliths in Terrestrial Carbonates: Classification, Recognition, Genesis and Significance: Sedimentology, 27, 613-629.
  • Lake Michigan Federation, 1999, Vanishing Lake Michigan Sand Dunes: Threats from Mining: Lake Michigan Federation, Chicago, IL, 36p.
  • Michigan Trail Maps, 2016, Rosy Mound Natural Area
  • Neal,W.J. and Wilson, G.C., 2014, Beaches of Sleeping Bear Dunes National Lakeshore, Michigan

Captain Sams Spit, Kiawah Island; By Cecelia Dailey

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By Cecelia Dailey

Since 2008, concerned citizens and environmental organizations have opposed the development of Captain Sams Spit, Kiawah Island, South Carolina.

South Street Partners (who purchased the holdings of Kiawah Development Partners) want to build 50 houses on this dynamic landform and critical wildlife area. The Coastal Conservation League and SCELP have been paramount through continued litigation. Experts including coastal geologist Dr. Orrin H. Pilkey have written against this project.

Dr. Richard Porcher (author of A Guide to the Wildflowers of South Carolina, field botanist, and professor Emeritus at the Citadel) raises two important concerns about the proposed development. There is erosion on the beach, which developers deny, and their calculation of “highland” does not appear to include the myriad of low-lying wetlands interspersed between dune ridges. The following account reveals the latest efforts by developers to sway public opinion.

On Saturday February 13th, 2016, Richard Porcher and I drove out to Beachwalker Park to investigate the viability of development on Captain Sams Spit. As we walk, we see clear signs of erosion all along the beach. Roots of plants are exposed in the sheared off dunes.

Patrick Melton, South Street managing partner, in his most recent op-ed on February 9th, says,“The beach on Captain Sam’s Spit is not eroding. Just the opposite in fact. The beach has accreted non-stop for more than 65 years.”

But, Richard sees evidence to the contrary. “There is no beach community due to erosion,” he says, meaning that typical plants such as sea rocket and Carolina saltwort, which are first to take hold on a beach, are not prevalent. These small plants are usually seen between the dune community and high tide line. Presence of a well formed beach community with its hardy plants and wide beach with active dune formation would be a clear sign of a recent period of accretion. That does not exist right now on the spit. Is this a recent change or something others have failed to notice? Is this a minor blip or a sign of a shifting trend?

There are bands of established dune ridges behind the beach which represent accretionary surges in the past. To use the word “non-stop” does not properly address that accretion and erosion are cyclical. This day’s walk is only a snapshot in the spit’s recorded history which has been characterized by change.

Since 1661, the spit has come and gone many times, according to Miles O. Hayes in A Coast for All Seasons (2008). Most recently in 1949 there was a breach, as well in 1922 and 1822, and it is safe to say there have been others. This is a typical recurved spit which has accreted, elongating across the inlet, then undergone severe erosion and breached again and again. Hayes estimates that in the past, intervals between breaches have been as short as 40-50 years. We circled around the end of the spit. Accretion had been noted here at the tip, where the inlet was recut last year. (Here is a video animating Miles Ol Haye’s documentation of the spit.)

Melton says of the spit, “In the last 20 years it has grown from 119 acres of highland to 160 acres. ” In his previous op-ed on June 6, 2015, he said there were 180 acres of highland. To our knowledge, the spit is a total of 150 to 180 acres, so we do not know how Melton came up with these figures. There are little pockets of wetlands and finger-like depressions scattered throughout the dune ridges in varying states of vegetation. Have these areas been included in his calculation of “highland”? To call so much of the spit “highland” is suspicious. (See reference)

These wetlands are significant as habitat for wildlife. The town of Kiawah has been studying migratory birds in these scrubby wet depressions for the past 8 years.

“Building 50 houses on 20 acres will have consequences for this sensitive area.”
— Cecelia Dailey

Melton tells us, “The backside is highly vegetated with mature trees and other natural coastal flora.” Presence of vegetation does not mean that a land is suitable for development; there is of course “natural coastal flora” on even the youngest beach. His statement puts us on a search for mature trees. What we find is what Richard calls an “incipient maritime forest,” one that is just starting to develop.

At high tide, we explore the salt marsh and salt shrub thicket. All along the backside of the spit, we see the wrackline washing right up to the treeline. We are searching for “highland” where developers propose to build. We trot through flooded ox-eye and Spartina patens in our tall boots up to the treeline. One of the largest trees is a live oak, which Richard says grows pretty fast, and not more than 40 years old, if that. We continue to charge through the brush and find a path that leads to the salt shrub thicket in a depression between dune ridges. Just a little elevation can allow for a tree to take hold. Tide water inundates this central depression of the spit. Young sabal palmettos, pines, cedars, and red bays are found in this low area. Just because an area is vegetated, even with trees, it is not necessarily high land or well drained.

We find the dune ridge where they could possibly build, maybe a few hundred feet wide, and elevated, we guess, about 15 feet. It’s hard to tell with the impenetrable brush which characterizes this young maritime forest community. Pine trees atop this ridge are 20-30 years old.

Building 50 houses on 20 acres will have consequences for this sensitive area. Dunes will likely be leveled in the process of construction and wetlands filled in. At points where vegetation has been killed or removed, dunes are more susceptible to erosion by wind.

We walk back into the dune fields behind the beach and take note of the cactus and yucca species. We imagine that the road must be placed as far back from the beach as possible. Still, the road will have windblown sands accumulating on it all the time. One of the most rapidly eroding parts of the spit is the backside, and right here at this point of connection to the mainland, it is the thinnest. It will eventually break through.

It is easy to see standing atop these dunes, viewing the ocean to one side and the river to the other, that storm surge at a high tide from even a small hurricane would drastically impact the dunes and beach face. Overwash and flooding from hurricanes is an inevitable threat. It’s been a while since any storm has directly hit our coast south of Charleston. It will happen again.

Developers agree that the backside is eroding. The steep bank of the backside of the spit can be seen from the parking lot at Beachwalker Park. Developers have sought a half-mile long sheet pile revetment to protect their proposed road. After flip-flopping decisions by the South Carolina Supreme Court, an Administrative Law Court judge has once again granted the developer permission to build the revetment. Melton says, “Our request for an erosion control structure includes protecting the park’s parking lot, which we think is in the public’s interest. But our opponents vigorously oppose our efforts to save Beachwalker Park.” We say “let nature run its course” and move the edge of the lot back as the river changes, a better alternative than a hard structure which would impact wildlife.

Melton says: “Our opponents claim that in the end the public will have to pay for our development.” If there is a hurricane, it will be the public who are cleaning up debris scattered all over. As well he says “Federal flood insurance, even in its limited amount, will not be utilized.” Captain Sams Spit does not qualify for federal flood insurance because it is in the Coastal Barrier Resource System, which is intended to discourage development of such a sensitive coastal area.

We want to protect our fragile coastal environments for many reasons. This kind of development has long been thought unwise. In the original plan of Kiawah Island, with setbacks determined by Miles O. Hayes’ team, Captain Sams Spit was reserved from development for good reason. Inlets and spits are notoriously dynamic features of barrier islands.

If you walk to the sites of the proposed houses yourself, you would understand the concerns of many vocal citizens. You would see a thin margin of trees, a dune field that takes up half the spit, clear signs of erosion on both sides of the land, and protected dune foliage such as sea oats throughout the landscape. You would hear the ocean breaking from every point of your walk.

We are environmentalists. We work for the benefit of all the generations that follow. A developer will make his quick profit on the site. Their investment in South Carolina is not the lasting legacy and benefit to humanity that we seek. The lifespan of a home site should be on the caliber of centuries.

I would like to repeat the words of Mr. Melton and urge the public to make an informed decision: “…arguments should not be based on false premises and inaccurate information. You, the public, and our legislators deserve better.”

We encourage education on the complexities of coastal geology and biological communities whether or not it leads to our opinion. We see Captain Sams Spit as improper development with its history of transformation and status as a critical wildlife site, especially in an uncertain time of rising seas and global change.


More on the subject:

Capt. Sam’s and shifting sands, The Post and Courier (03-30-2016)
The dispute between those who would build houses on Captain Sam’s Spit and those who would keep that from happening has been festering for four and a half years. It’s been one step forward, one step back. Or one step backward and one step up, depending on your perspective.

Capt. Sam’s Spit road gets court go-ahead; conservation groups plan to appeal, SC, The Post and Courier (03-24-2016)

Captain Sams Spit back in development headlines, Charlestone Currents (11-23-2015)
Captain Sams Spit is in the crosshairs of development again. The Spit is a 150-acre pristine sandy land mass at the southern end of Kiawah Island, relied upon by the piping plover, diamondback terrapin, bottlenose dolphin, and other rare and threatened species for nesting and feeding…

Battle over Captain Sam’s Spit grows as coastline shrinks, Charleston City Paper (11-19-2015)

Editorial: Due process needed in coastal development cases, The Island Packet (11-18-2015)

Kiawah Developer Denied Permits for Capt. Sam’s Spit Sea Walls, SC, The Post and Courier (12-10-2014)
The South Carolina’s Supreme Court has ruled against granting a permit for a sea wall and revetment on Capt. Sam’s Spit – the wildlife-rich, 150-acre spit that is a prized piece of disappearing natural coast…

Part 2: Excursions in Cape Romain; By Cecelia Dailey

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By Cecelia Dailey

Through a series of excursions, I bring to you some ground-truthing in Cape Romain National Wildlife Refuge, SC as an amateur naturalist. My friend Charlie McAlister often navigated these waters with me in his small wooden skiff. For an examination of the geology of the Cape Romain area, see Part 1: Decoding the structure of Cape Island.

Over a year ago in November 2014, Charlie and I arrived at Cape Island early in the day. It was a high enough tide to pass over the shallow waters near the wide breach in the center of the island.

The tide fell and we were left at the beach all day. Sea Oats and Sweetgrass were established on the beach away from the ocean’s edge. A little cliff defined a line behind which older vegetation thrived. Mud with clams embedded and the cut-off roots of Spartina lay in huge chunks on the shoreline. This is evidence that where the mud on the beach is located was once marsh, the backside of an island, protected by a beach once offshore from here. Spartina, gone to seed, thrives behind the island where washover has not yet occurred.

The beach is steep and receding. As sand washes into the forest, life struggles to hang on. Classified as a thin, retreating barrier island, Cape Island is on a slow crawl landward. Eventually this inundation will incorporate the marsh behind it, resulting in the conversion of salt marsh to tidal flats, then to open ocean. (1) The sand can move with the rising seas but the marsh will struggle to survive.

In summer when oysters are out of season, many turn to crabbing or clamming to make their living in Cape Romain National Wildlife Refuge. Crabs molting in the spring allow for a short soft shell crab season. A building filled with tanks on the bank of Jeremy Creek in McClellanville, SC serves as a holding facility for the crabs, moved from tank to tank by hand as they begin to molt. Having been acquainted with Darryl and Ronnie who manage the crabs at Livingston’s Seafood, I walked up and bought two for dinner wrapped in paper on a spring afternoon.

An excursion to the clam beds with Julie McClellan and her business partner, Irving, allowed me to see the process of raising clams in the natural environment in the early summer. Moving through the curving waterways, Spartina blocks the view from the deck of the small boat. Julie points out an old tower used as a place marker which was turned over in a storm last winter. Crabbers, clammers and shrimpers are out here working in the waters that have just gotten warm. The clammers mark their plantings with rebar or PVC pipe. Passing in the early afternoon, I see the DNR has thrown a cast net along the river bank, surveying all the creatures found.

The day I observed the clamming, we collected bags previously placed in a hard-bottomed creek with flow from the ocean moving through to clean the clams. These bags had been placed there the day before, moved from the muddier location. Later in the day, we collected bags from the mud, pulled up by hand and hosed out in the water with a gas-powered pump. These bags were motored back to the creek spot when the tide was lower and could be tossed out into the center of the creek. The rushing tide will leave these clams pristine when they are collected, to be sorted and counted the next day.

Clam seed is bought then raised over many months in mesh bags or placed under grating in the mud. This prevents predation and these areas are marked to allow clams to be moved so that they aren’t buried by sediment. Clams do better with the grating system, Irving says, because it is a more natural environment and less mud collects on the grating than with the bags. Bags make the collecting and moving of clams much more efficient however.

Charlie is here for the summer and ready for some exploring in Cape Romain. We exit Jeremy Creek from the McClellanville public boat landing and pass over the Intracoastal Waterway, into where the broad Five Fathom Creek goes south toward Bulls Bay and the ocean. Near the inlet of Five Fathom Creek is tiny Clark Creek on Raccoon Key, our destination. But on this day in early August, we don’t get that far. His motor is acting funny so we don’t want to push it.

Oyster shells are piled up on the banks, shining brightly in the sun, along the east side of Five Fathom as we approach the ocean. Wrack lines of marsh grass on the shell banks show evidence of three recent storms. (2) The shells are bleached by the sun and some are riddled with holes from oyster drills. I don’t see any sign of living oysters on this creek. Lime green Saltwort and the bluish Southern Sea Blite grows lushly in the shell piles and Spartina abounds into the marsh.

Riding out to the end of Five Fathom Creek, the depth is over 30 feet, but becomes shallow quickly where Sandy Point disappeared below the water. Sandy Point was the mile-long spit of Raccoon Key used to obstruct the inlet to Five Fathom Creek. By 1994, Sandy Point had disconnected and by 2006 was nearly gone, rapidly eroding thereafter. (3) Swells prevent our crossing of Five Fathom Creek. Waves break over the shoals and strike the steep bank.

After discovering extensive rot in Charlie’s boat, we spent two months digging it out, filling holes and painting the wooden hull. On Labor Day, we rode out toward Cape Island, in the Cape Romain National Wildlife Refuge, but decided to walk on Lighthouse Island first. We rode up a small creek to the backside of the island. Where we landed, there was active dune formation. A huge waterway maker and a massive float for an artificial reef were washed up on the shore, among crab traps and other debris. Lines of black sand (likely magnetite) were interlaced with the white quartz sand and the wind had made fine ripples across the beach. (4)

“Cape Romain will keep revealing its secrets to those that listen. ”
— Cecelia Dailey

We walked up the beach from the west and the scene grew increasingly desolate. Chunks of mud began to appear on the beach. Almost all the plants were gone where there used to be thick vegetation at the end of the island. There was barely a dune line with a small patch of Sea Oats hanging on. The sand was washing over into the marsh creeks. Since last year, it looked like almost all the Spartina grass had died and a small creek was now a few hundred feet from breaching here.

Across the inlet, the sandy southern spit of Cape Island has about ten people out with their umbrellas and chairs, and a few boats are anchored in the inlet enjoying the holiday weekend. On the end of the island, the dunes are high, and the water looks even higher.

We return to the boat so that we can approach the southern spit from the other side of the lighthouse. It is high tide, otherwise the silting of the inlet here would stop us from taking this route. Tongues of sand extend below the water and a curling tip of sand flows back into the inlet.

We attempt to go north and see more of Cape Island, but as we approach the new inlet in the center, we encounter unknown sand bars. Newly formed sand islands have signs posted that mean they are temporarily closed as bird habitat.

At the end of September, after a seven foot high tide (infrequent here on a mesotidal coast) and weeks of rain, we went out to see the north end of Cape Island. (5) The water was amber-brown with fresh water. Organic matter from the runoff made patches of suds in the turbulence. (6) Even though summer is only passed by a few days, winter looks like it has taken hold on this overcast day. The wind is blowing from the north, straight into our faces. The north wind is typical of the winter season. A cool front has stagnated, so we are free from the storms that we see in the distance. We take an entrance to a small creek we’ve never taken, avoiding the open waters of Muddy Bay where the chop would spray us.

This is Ramhorn, a very skinny, winding creek. We begin to see Black Needle Rush mixed with the Spartina as we move only a mile or so north of our McClellanville departure. Rush requires more fresh water than the more salt-tolerant Spartina varieties. The Santee Rivers, about 8-10 miles to the north, contribute abundant fresh water to this area, but the irregular distribution of Needle Rush is more complex than that. Right here in Ramhorn Creek, the Rush grows on high, clay banks. As I stand up on the bow as we ride, I observe pockets of rainwater trapped in pools. My guess is that this is an older creek, at slightly higher elevation, and the clay substrate (as opposed to the silty, muddy conditions normally encountered) has kept the rainwater from draining completely.

The Rush is deep brown, frosted gray by mist, prevalent along the land, but diminishing toward the ocean. We make it out of the creek and cross over Cape Romain harbor, looking toward the low-lying Cape Island, here at the north end. Anchoring, we explore the beach, walking up the little creeks that drain the backside of the island, and refuse such as crab baskets, navigation signs and even the floorboard of a wrecked vessel have collected. We observe the old oak knees connected to cedar planks by metal nails capped with plugs of wood. We find a rusted trap that perhaps was used to capture raccoons. (When was this trap used? It is a peculiar find. If it predates establishment of the refuge area in 1932, it seems like it should have rusted away by now.)

The plant life here is crushed by the tide. Saltwort, grasses, and Prickly Pear cactus survive the frequent flooding and constant salt spray. Abounding are Seaside pennywort, with long drought-resistant roots, and Beach Pea, a leguminous vine with a green bean-like pod. There is a sandy bank about 100 feet wide, and the higher, older portion of the island is defined by a small cliff that is slowly eroding.

The distance to the ocean-front beach is about ¼ mile across this recurved spit. Dunes on the shore are visible, and the Sea Oats that hold them in place on the horizon. We get back in the boat and motor up to the tip of the north spit. The wide sandy bank here is a feat of nature, seeming to grow in spite of tremendous tidal forces.

The mist is growing thick and we must rush home this afternoon. We take note of the many varieties of marsh birds that make a quick retreat out of the high grass as we move by and we spot a few bald eagles along the waterway nesting up in pine trees. Dredge spoil forms high banks and harbors some invasive species such as the bamboo-like Arundo donax, or Giant reed. Other species found in disturbed areas here include hackberry, chinaberry and honeysuckle. (7)

In mid-October, I took a walk across the narrow northern spit of Cape Island after we travel half an hour by boat from the village. A variety of shrubs, slow-growing cactus and yucca can be found on this oldest part of the island. On the beach, every few hundred yards are creeks that flow into (and drain) the island. The wrack of Spartina grass provided a pathway to walk on, then I found a sand ridge where Seaside Goldenrod and yellow Camphorweed were blooming and try to avoid the thick boggy patches of Oxeye which are coarse and scratchy. These sand ridges come in bands that have developed northward over time, growing like an oyster shell.

Fruiting cactus and Spanish Bayonets were surviving on the higher sandy patches. These plants are important to stabilization as they capture windblown sand, seen at their bases.

We came here two weeks ago but the soggy conditions made this walk impossible. A line of Sea Oats hold the dunes here, only a single row. I find a low spot to walk through to access the beach. If this place was more accessible, it would not be in such natural condition.

I come out on the beach to see surprising geometry in the sand. A line of triangle-shaped ridges (only a few inches high) are equally spaced, punctuating the beach. This is an intriguing pattern, and I guess it must be the result of forces colliding on the beach, perhaps waves striking each other from opposing directions to create these regularly spaced triangular bulges. I’m not sure exactly how to read these lines in the sand.

On the way back from Georgetown on October 18th, we detoured to see the central breach in Cape Island again. We approached from the edge of the point to avoid the unknown hazards from silt and sand in the water behind the beach. The tide was coming in so there was limited view of the low-lying sand formations.

There was overall less shell material, including oysters, on the beach on this trip than when we were here a year ago. Large chunks of mud on the beach had been washed away, but mud patches could still be seen at this tidal height at the open ocean. Some small balls of mud were scattered on the beach, hardened by the sun.

Vegetation was crushed and there were fewer Sea Oats, some of which look dead in the sand, as the ocean has crept forward. The beach was scattered with broken foliage. To the north, a forested area which extends across the island in a band remains at the ocean’s edge. Where the trees are being inundated, the beach is gone.

Cape Island seems destined to be two pieces now. I suspect this breach will grow wider, with sand accumulating on both sides of the breach composed of material eroded from the beaches nearby. The beach is not just what we walk on, but all the sand that lies underwater that feeds the beach. A new sand formation might remain and accrete or get washed landward in the next storm. If plants colonize here where the birds have collected on the new sand, this ground may gain traction against the forces of the open ocean.

In December I spent a couple of weeks house sitting for the Fulchers at a remote location down two long dirt roads on the mainland adjacent to the Cape Romain National Wildlife Refuge. Jim Fulcher says he’s lost 20-some odd acres to the rising sea level. He retired last year and was the town doctor in McClellanville for 40 years. He and his wife Patty bought 140 acres on the marsh at Cape Romain years ago, before Hurricane Hugo, and many of their friends share this wooded backyard.

Black Needle Rush, he says, is what defines his land from what is federally-owned. Coastal law prevents them from building on this land. Until they get it surveyed again, they pay taxes on all of it. (8) The Rush grass creeps in along the sides of a dirt dike that leads out to a promontory, populated with pines, oaks, cedars, and palmettos. Bright red Yaupon holly berries and clusters of black Smilax berries overflowed on bushes along the dike’s bank. (9) A huge grey heron took off from a pool surrounded by the rush as I make these notes. This area was carved up with dikes by enslaved people, who removed vast treed swamps to create controlled floods for rice cultivation. Perhaps this dike is one of those remnants.

Hummocks and islands float on the horizon, and from the edge of his land on a clear day, you can see the Cape Romain lighthouse, about 8 miles away. Small creeks meander up behind forested islands and cut the higher elevation land into pockets of trees. Going out by boat here requires at least a half tide on this tiny creek.

Many plants thrive on the sandy island including mosses and grasses too numerous to name. Wiregrass should be noted because it is so integral to the pine forest here. A more wooded area has branches, pine needles and other organic matter remaining in place, improving the soil quality. When it rains, this land becomes a swamp. There are taller grasses, shrubs such as groundsel, calf-high hollies, and flowers gone to seed such as Goldenrod below the pines. Seeds blowing in the wind stuck to my jacket. Vines of small blackberry and Smilax were all over the ground ready to snag my leg.

In the morning duck hunters can be heard blasting. Abundant berries in these woods attract many deer for the interested hunter. Quiet walks around this property stand in peaceful contrast to the force of geologic time and the span of life that harnesses beautiful diversity, yielding opportunity for endless observations. Cape Romain will keep revealing its secrets to those that listen.

References:

  • (1) USFWS
  • (2) The wrack line is the debris left by a high tide. Wrack lines act like mulch, retaining water and allowing a protected environment for seed germination. Sand accumulates around any object or vegetation on the beach, including wrack lines. “This sand-trapping effect of natural wrack lines is a strong argument for leaving them on the beach rather than ‘cleaning’ the beach.” Atlantic Coast Beaches: A Guide to Ripples, Dunes and other Natural Features, Neal, Pilkey, and Kelley, pg 178, 185.
  • (3)USFWS Sea level rise on Cape Romain
  • (4) Mostly silicon dioxide or quartz compose sand but many different minerals occur. Weathering of bedrock on the continent are transported to the coast by rivers. Quartz is resistant to abrasion and makes it hundreds of miles to the beach. Common are also heavy or black minerals, which concentrate in troughs or ripples. Magnetite is the most common heavy mineral in sand, and is a common iron oxide mineral. Atlantic Coast Beaches: A Guide to Ripples, Dunes and other Natural Features, Neal, Pilkey, and Kelley, pg. 74, 83-85.
  • (5) The South Carolina coast here is mesotidal, meaning it has a tidal range of 2-4m. The Geologic Impact of Hurricane Hugo and Post-Storm Shoreline Recovery Along the Undeveloped Coastline of South Carolina, Dewees Island to the Santee Delta, Sexton & Hayes, Journal of Coastal Research, Spring 1991.
  • (6) Atlantic Coast Beaches: A Guide to Ripples, Dunes and other Natural Features, Neal, Pilkey, and Kelley, pg. 114
  • (7) Tracing the Cape Romain Archipelago, Bob Raynor, pg. 37
  • (8) USC School Of Law
  • (9) Smilax is the genus of over 300 species including the many prickly briers, also called catbrier, greenbrier, and chainey briar.

Cape Romain – Part 1: Decoding the structure of Cape Island; By Cecelia Dailey (02-01-2016)

Cape Romain – Part 1: Decoding the structure of Cape Island; By Cecelia Dailey

4-2

By Cecelia Dailey

Cape Romain is South Carolina’s only cape and its most erosional coast. (1) Here is a vast estuary, with beaches miles offshore, only accessible by boat. Behind the beach is a labyrinth of islands and creeks, mostly low lying and muddy, though some have trees and abundant foliage.

Change is happening rapidly here. Shores and entrances to inlets at the edge of the open ocean are receeding. Some land has completely disappeared. The fishing chart sold at the general store looks to be over 30 years outdated. Called a cuspate foreland, the triangular formation extends 8 miles off the coast at its point. (2) Shoals extend miles offshore and keep the beaches alive, feeding them with sand.

Last year, I lived in the town of McClellanville, landward of the Cape Romain National Wildlife Refuge. Of greatest interest to me there is Cape Island, an (approximately) north-south oriented barrier island, with sand spits growing on both ends. The north-pointing spit is the largest recurved spit in South Carolina and is fairly stable, very different from the rapidly changing southern spit.

In South Carolina, the predominantly south-flowing longshore current generally creates spits pointing to the south. Here, offshore shoals refract waves and contribute to the unique north-pointing spit of Cape Island. (3) Miles O. Hayes cites “unusual shoreline orientations at the Cape” as one reason for the recurved spits prograding “in two opposite directions.” (4) The shoals, reshaped over time, are a product of the Santee River delta, north of Cape Romain. Before a dam was built in 1942, the Santee “carried to the coast one of the heaviest sediment loads of any river on the east coast.” (5)

Wind also accounts for the shape of Cape Island. According to Hayes & Michel “cuspate forelands are most common on shorelines with two opposing wind directions” because the wind generates waves from opposing directions. (6) In the winter, storms come from the north and the southern spit will likely increase. Nor’easters can move slowly over the coast with sustained power. In the summer, the southern spit of Cape Island, and the southern flank of the cape face the wind. Hurricanes can bring dramatic instances of storm surge, wind and wave actions that carve these islands.

Lighthouse Island and Raccoon Key compose the southern flank of the cape. Toward the lighthouse, the dune fields are almost totally crushed, washover is perpetual, and new inlets often form where the beach in front of tiny creeks is eaten away.

Major changes can be seen since the first 1989 satellite photograph was taken of this area. The southern spit shows its animation; accumulated sand grew over the inlet from 1989 to 1994, paralleling the beach at Lighthouse Island for the entire length of the island and blocking the inlet. By 2005, the elongated spit had broken off, opening the inlet again. By 2013, it became clear that the southern spit was forming to cover this inlet again.

Three breaches were made in Cape Island in 2011 with the hurricane event, Irene. (7) One of the breaches healed itself quickly, while the other two and the land between completely washed out to create a new inlet dividing Cape Island in half. Despite the rapid erosion at the new inlet on Cape Island, the relatively stable north end supports a diversity of plants and the southern end has active dunes and a highly dynamic accreting sand spit.

The mainland here maintains its rural nature. McClellanville is surrounded by protected habitats including the Francis Marion National Forest and Santee Coastal Reserve. Those who ventured to live on the Cape Romain islands have been few. Seewee indians occupied many creek banks, leaving behind shell middens found up and down the coast. The Lynch family, one of the founders of McClellanville, had their summer home on the Cape islands sometime after 1750. The hurricane of 1822 prompted those living at the mouth of the Santee to move inland, and the town of McClellanville was born. (8) A lumber mill operated by wind was once near the Cape Romain beach, sawing timber brought by boat from the Santee, en route to Charleston. By 1822, steam had taken over as the latest technology, which could be used on site where trees were being cut, and the sawmill was obsolete. Lighthouse keepers had a residence near the lighthouse, now gone, which they landscaped with ornamentals and fruit trees. (9)

“Cape Romain’s beaches and islands are spectacular locations to see the forces of coastal change at work. ”
— Cecelia Dailey

If we could go back a thousand years, what would this place look like? Even a couple hundred years ago, we know the marsh islands were much larger from historic accounts. Early maps show the general triangle shape, and in the 1900s, maps show the hook-like southern end of Cape Island and warn of the shoals here. (10)

Cape Romain’s marsh islands are largely silt and clay. Once suspended in water, these fine particles are moved more easily than coarse sand. (11) This is one clue to decoding the complex morphology of this area. On a mesotidal coast (as found in South Carolina), the ebb-tidal (outflowing) delta is much larger than the flood-tidal (incoming) delta deposits, another clue which accounts for the seaward shoals found at inlets. 12 miles off the coast of the active Santee delta front line “a complex of reworked deltaic deposits” which give a ghostly, perplexing impression of where islands might have been long ago.

The Santee River’s delta was once much more vast, composed of this mixture of sediment, sorted by the action of wind and waves. The Pee Dee River and several other rivers empty into Winyah Bay near Georgetown, one of the largest watersheds on the east coast (18,000 square miles and stretching to the border of Virginia). The entire Santee/Pee Dee area from the inlet at Winyah Bay to the point of Cape Romain is an approximately 18-mile stretch which is the “largest deltaic bulge on the east coast of the United States” according to Miles O. Hayes. (12)

Hayes says that Cape Romain does not conform to the general morphology of the other Carolina capes (Fear, Lookout, Hatteras) as Romain’s flanks are relatively symmetrical with significant longshore sediment transport to the north. Some of the unique factors that Hayes speculates on include: “Sheltering of the cape from the dominant northeasterly waves at the present time (to some extent) by the mass of the Santee Delta, as well as shoals offshore of the delta. The rapid retreat of the cape over the past few hundred years conceivably moved the present form further into the shadow of the delta than when it first started to develop. In early years, it may have had the morphology as the other capes, because it was more exposed. The bathymetry of the shelf off the present cape shows that complicated shoals now occupy the space where the cape was formerly located.” (13)

From the aerial images, you can trace the lines of change on some landforms. (14) Landward of the Santee are “multiple, parallel highstand beach ridges” which are bands adjacent to the delta from the late Pleistocene (2.6 million to 11,700 years ago). The Santee dissected these ridges during the “Late Wisconsin sea level lowstand” (about 18,000 years ago). At the time of the early Holocene when sea level rise began to slow to a steady rate (about 6,000 years ago), barrier islands formed in equilibrium with the forces of change, and the Santee delta likely began to resemble what we see today. The northern spit of Cape Island shows rings of growth northward of at least several hundred years. (15) In this flooded landscape, low-lying evidence is rewritten and rearranged. Dams upstream remove sediment from the waters of Santee now, but allow water flow, contributing to erosion here and down the shore. (16) This area will remain the most erosional in South Carolina, revealing the reality of sea level rise from the minuscule to the aerial view. Cape Romain’s beaches and islands are spectacular locations to see the forces of coastal change at work.

References: Cape Romain – Part 1:

  • (1) “A study by one group published in 1975 showed that, except for the outbuilding recurved spits at each end of the Cape, the shoreline retreated about 20 ft per year between 1941-1973. Based on later observations, this rate of retreat has increased.” A Coast for All Seasons, Hayes and Michel.
  • (2) Cuspate forelands are “triangular-shaped features composed of sand and/or gravel that project either perpendicular or at a small angle to the overall trend of the shoreline.” A Coast for All Seasons, Hayes and Michel, pg. 170-174.
  • (3) “Cape Island, which makes up the northernmost flank of the Cape, is composed of half recurved spit and half transgressive barrier island. The spit projects in a northerly direction, presumably as a result of refraction of waves around the shoals offshore of the Cape.” At entrance to Santee rivers, there are recurved spits on the northern side. “These entrances are major mesotidal inlets with associated recurved spits on their northern (updraft) sides and large ebb-tidal deltas.” The Geologic Impact of Hurricane Hugo and Post-Storm Shoreline Recovery Along the Undeveloped Coastline of South Carolina, Dewees Island to the Santee Delta, Sexton & Hayes, Journal of Coastal Research, Spring 1991.
  • (4) Beach Erosion in South Carolina, Hayes, Moslow, and Hubbard, Coastal Zone Information Center.
  • (5) A Coast for All Seasons, Hayes and Michel, pg. 155.
  • (6) Cape Romain is unlike the other capes in North Carolina which are eroding on the north sides with spits that grow to the south. Cape Romain is relatively symmetrical, perhaps because it has been shielded by the large Santee River Delta and as it has eroded, moving landward. A Coast for All Seasons, Hayes and Michel, pg. 170-174.
  • (7) Cape Romain Aerial: Post Irene (video), DNR.
  • (8) Design Review Manual
  • (9) Tracing the Cape Romain Archipelago, Bob Raynor, pg. 45-47.
  • (10) Some links to early maps that include Cape Romain (also spelled Cape Roman and called Cape Carteret): 1671; 1764; 1775; 1791; 1909.
  • (11) Atlantic Coast Beaches: A Guide to Ripples, Dunes and other Natural Features, Neal, Pilkey, and Kelley, pg.73.
  • (12) A Coast for All Seasons, Hayes and Michel, pg. 154.
  • (13) A Coast for All Seasons, Hayes and Michel, pg. 174-175.
  • (14) Aerial photographs were taken by Mary Edna Fraser in 2006. Her aerials show the terrain’s geography and also the shape of dunes and other details revealed in the oblique view.
  • (15) A Coast for All Seasons, Hayes and Michel, pg. 174.
  • (16) The “accelerated rate of erosion on the Cape in recent years is probably due, at least in part, to the diminished sand supply to the Santee River delta as a result of the building of the dam on the Santee River in 1942.…15 miles to the north of the arrowhead point of the cape.” A Coast for All Seasons, Hayes and Michel, p. 174.

Dog Island, Florida; By Orrin H. Pilkey & Norma Longo

Figure-2-swash-lines

By Orrin H. Pilkey, Nicholas School of the Environment, Duke University, Durham, North Carolina, and Norma Longo, Nicholas School of the Environment, Duke University, Durham, North Carolina

Dog Island is a 6.8 mile-long, east-west trending barrier island along the so-called “forgotten coast” of the Panhandle of Florida, in the Gulf of Mexico. (See map, Figure 1.) The island ranges in width from one mile to 200 yards. The name Dog Island may be based on the fact that there once were wild dogs on the island. Another possibility is that indentured sailors known as “Sea dogs” were temporarily put ashore on the island when sailing ships came into the Carrabelle River (Apalachicola’s closest deep-water harbor), so they wouldn’t jump ship. During the 17th and 18th centuries, the island was a haven for smugglers.

Several lighthouses have been in service on the island, but regardless, many shipwrecks occurred in the area. In 1838, the first Dog Island lighthouse was built, only to be seriously damaged within 4 years by the 1842 hurricane. The following year, in 1843, a new wood-framed lighthouse was built which successfully weathered the hurricanes of 1844, 1846, and 1850 but did not survive the hurricane of 1851. In 1852, a new brick lighthouse was built which was partially burned by the Confederates during the American Civil War in the 1860s, to prevent use by Union soldiers. Interestingly, the light in this lighthouse used 423 gallons of whale oil per year. In 1873, a storm destroyed it, the last Dog Island Lighthouse. Another one was never built on the island.

” Dog Island is a marvel of barrier island development policy.”
— O.Pilkey

This 1852 lighthouse now resides (in fragments) on the bottom 100 yards offshore. In total, the location of the lighthouse remnants indicate 300 yards of shoreline retreat since it was built, because it initially was 200 yards inland from the beach. The latest lighthouse, Crooked River, was built near the town of Carrabelle on the mainland, several hundred yards inland.

Dog Island was part of Camp Gordon Johnston and was used for training soldiers for the D-Day landings in World War II. After the war, the entire island was purchased for $12,000 by businessman Jeff Lewis, who later sold about 75% of it to The Nature Conservancy. Much of the island is covered with a forest of slash and longleaf pines, and grasses grow profusely on dunes. Sea grasses often accumulate in swash lines on the beach. (Figure 2)

As things go in Florida, the island currently is very lightly developed, with about 100 houses (Figures 3, 4), plus a private boat landing and docks, mis-named the “Dog Island Yacht Club”, where islanders park their land vehicles and their boats on the bay side of the island in Tyson Harbor, on St. George Sound. The island is without a bridge, but the “Dog Island Conservancy” has a small ferry on which only Islanders can arrange service from Carrabelle to the Yacht Club basin.

Dog Island is a marvel of barrier island development policy. Most beachfront lots measure about 100 feet wide and 500 feet deep. Seawalls are not allowed and houses are either moved back as erosion catches up, or the buildings are allowed to fall in. For these reasons, future generations will still have a beach on Dog Island.

Two small (illegal) wooden seawalls have been constructed along the front of the island. One is in front of an individual cottage and the other is protecting a lot where a cottage once stood, yet was swept away regardless of its seawall. (Figure 5) Both walls are likely to disappear in the next major storm and contribute debris to the beach and the waters of the Gulf.

In recent years, some 15 houses have fallen in. Clean-up of the debris is accomplished by the community (the “District) rather than by the owner who abandoned the destroyed house. A number of other houses have been moved back from the shore on their long lots and a few have been moved to new upland lots. During a boat trip around the island (captained by islander Eddie Hudson and accompanied by naturalist Dan Tonsmeire) in November 2015, we observed about 10 houses that will likely fall in during the next storm–if they are not moved. (Figure 6) Among them is the Pelican Inn, a well-known tourist facility (the only one on the island), as it is almost entirely out on the beach. (Figures 7, 8) No other commercial development is allowed and even the renting of cottages is discouraged.

“Seawalls are not allowed and houses are either moved back as erosion catches up, or the buildings are allowed to fall in. For these reasons, future generations will still have a beach on Dog Island.”
— O.Pilkey

The Ausley cottage on the very narrow island segment near the west end of the island was constructed 50 years ago on the bay side. (Figure 9) Today, the house sits adjacent to the beach on the ocean side of the island, startling proof of island migration. The house has been destroyed by storms twice and was rebuilt each time.

Judging from spit construction on both ends of the island, sand on the beach is being transported both east and west. The large size of the spit at the east end of the island indicates that sand movement to the east is dominant.

The beach is very well-sorted, fine to very fine sand with striking white color. We observed no visible black sand (heavy mineral) concentrations. Presumably the lack of black sand and the uniform white color reflect the fact that Dog Island is a long way from its ultimate Appalachian Mountain source of sediment. In other words this is a very mature sand. Tree stumps on the beach are common. Less common are pilings from long-lost buildings. (Figures 10, 11)

Dunes on the island are sporadic, mostly in the island interior. The sand is the same startling white color as the beach sand. A few dunes are 40 to 50 feet high, but most are about 10 feet high or less. (Figures 12, 13) At several beach locations, 3- to 4-foot high dune scarps are present, indicating very recent erosion activity. (Figure 14)

Shell content is low in the fine white sand, which appears to be pure quartz/feldspar. The overall grain size distribution of the beach is bimodal, with fine quartz/feldspar sand and a small amount of coarse shells. Brown staining of shells in the coarse fraction is minor and black staining of shells is even more rare. The brown staining is presumably a beach-derived characteristic whereas the yellow color is iron oxide in the form of the mineral limonite. The black-stained shells likely derive their color from burial in a reducing environment, lacking oxygen, where iron sulfide forms.

Several aspects of the Gulf-side beaches of Dog Island are quite different from their counterparts on the east coast of Florida.

  • The bright white sand is probably a reflection of the sand’s high maturity and lack of iron-producing heavy minerals.
  • “Barking sand” with a high frequency noise is found almost everywhere on the Dog Island beaches. It occurs in the dry sand above the high tide line. “Barking” is more common in fine sand that is well sorted, which is characteristic of Dog Island beaches. On the East Coast of the U.S., barking sand tends to be found in patches and is much less widespread.
  • Shell Orientation. Large clam shells are usually oriented concave side down on the beach within the swash zone. This is the stable position for a clam subjected to swash currents. But on Dog Island we observed several instances of patches of large clam shells oriented concave up. (Figure 15)

Dog Island, with its beautiful white beaches, is one of the best examples in North America of environmentally sound beachfront development. In Florida it is particularly unique.

Acknowledgements:

Thanks to Flip Froelich, Eddie Hudson, and Dan Tonsmeire for their help with gathering some of this information.

Isle of Skye – Coral Beach, Scotland; By Gary Griggs

Figure-1-isle-of-skye-gary-griggs

By Gary Griggs, Distinguished Professor of Earth and Planetary Sciences, Director Institute of Marine Sciences, University of California, Santa Cruz, California

While on a circumambulation of the coast of Scotland in September, we noticed a description of a must see place, Coral Beach on the Isle of Skye. We were spending four days on Skye so decided to find this somewhat strange sounding beach. This name came as a surprise, mainly because Skye is situated at a latitude of 57.3 degrees north, nearly the same as Juneau, Alaska, and a coral beach seemed extremely unlikely.

The Isle of Skye is the second largest island in Scotland, and one of the Inner Hebrides along the nation’s west coast. It consists essentially of a number of peninsulas separated by bays that radiate outward from a mountainous central region, the Cuillin hills. Some of the oldest rocks on Earth are found on Skye, metamorphic gneisses that were formed about 2.8 billion years ago. There are also much younger volcanic and sedimentary rocks, including some spectacular columnar jointed basalts, which are exposed in the 300-foot high seacliffs at Kilt Rock along the eastern coast.

While situated almost as far north as Juneau, the offshore Gulf Stream helps to create a somewhat milder climate than might be expected, although its far from tropical, even in the summer months. But it makes for wild and unpopulated beaches.

Human occupation of Skye extends back many thousands of years into the Mesolithic period, or Middle Stone Age, and includes a period of Norse rule followed by clan domination. Today the population is about 10,000, and at 640 square miles, the population density is quite low. While a short ferry ride used to be the only access, a highway bridge completed in 1995 now connects Skye to the Scottish mainland, making visiting much easier.

“…this entire cove is covered with the calcium carbonate skeletons of the coralline algae, giving it a white tropical appearance.”
— Gary Griggs

While the Isle of Skye is famous for many things, great beaches are not high on the list. But in the local language, there are a few wee gems on Skye, and the Coral Beach at Claigan is one of them. It’s combination of accessibility and white sand make it an attractive destination on a warm sunny day, if you can manage to be there on a warm sunny day. It’s easy to find once you locate the Dunvegan castle, which has been the home of Clan MacLeod since the 13th century. The castle is generally believed to have been inhabited by a single family longer than any other home in all of Scotland.

Take the narrow road north from Dunvegan, past the castle, and follow it to its end at Claigan. Roads are narrow almost everywhere in the Highlands of Scotland, and driving on the wrong side of the road and from the wrong side of the car provided me with four weeks of automotive dyslexia and nearly constant anxiety.

There is a small car park at the end of the road, a sign with an explanation of the area, and a gate, which opens to a farm track leading towards the shoreline of Loch Dunvegan. The start is not particularly promising, but be patient, watch for what the cattle have left behind, and stay on the path. The walk is about a mile or so, and you pass along some gravel and cobble beaches, a small “coral” beach, before stepping across a small stream, passing through a gap in an old stonewall, and continuing uphill along a grassy path. As you reach the top of the slope you will see the coral beach a short walk ahead.

To be clear, the beach is not strictly made of coral, which do have some temperature constraints, at least the hermatypic or reef-forming corals. They prefer water between about 68° and 90° degrees F. or 20° to 32° C. The water just doesn’t get this warm around Skye. The beach actually consists of coralline algae, which form skeletons of CaCO3, and which persist long after the little plants die. And this entire cove is covered with the calcium carbonate skeletons of the coralline algae. There are a few bits and pieces of black volcanic rock, but 95% appears to be the carbonate skeletons, giving it a white tropical appearance. This particular coralline algae is know as maerl and beds of this algae grow along the Atlantic coast from Portugal to Norway. They do need to live where light penetrates so are restricted to about the upper 100 feet. Historically the deposits of the calcium carbonate skeletons were dredged and crushed and used as an agricultural fertilizer. But on the Isle of Skye, at Coral Beach, you can just enjoy their deposits along the shoreline and imagine you are on some tropical island, except that the ocean is a bit colder.

Cape San Blas, Florida; By Celie Dailey

fig-9

By Celie Dailey;

The remote Cape San Blas on the Florida Panhandle is photographed here in the fall. Huge vegetated dunes and many trails for exploration can be easily accessed from the tent sites at St. Joseph State Park. Pine forest is the setting of the camp.

Cape San Blas is a cuspate foreland, a body of sand in a triangular formation, similar in shape to the Carolina capes and Cape Canaveral. (1) On the Apalachicola River Delta, Cape San Blas is part of a barrier island chain along Florida’s northwest coast that stretches westward, across the bay of Mobile, AL. Cape San Blas is the southernmost headland at the “elbow” of two peninsulas, called “unstable strips of sand” in the text Living on the Edge of the Gulf, Duke University Press. (6) To the west is St. Joseph peninsula, mostly about half a mile wide, bordering St. Joseph Bay, and to the east of Cape San Blas is Indian peninsula. Further east is another set of barrier islands in a triangular formation—Saint Vincent Island, Saint George Island, and Dog Island.

Shoals feed the islands with sand. The source of the large shoals of sand “extending seaward from each cape” is “somewhat of an enigma to coastal geologists,” according to the text Living with Florida’s Atlantic Beaches, Duke University Press. (1) Likely, a river delta formed when the sea level was lower, and later flooded with the rising seas.

Much of “the sand on the Panhandle coast derives from rivers as far away as the southern Appalachians and Piedmont,” reflected in the build up of the Apalachicola River Delta, which was “derived long ago from sources that are no longer adding new sand to the overall system.”(4,5)

“Erosion is not a problem for beaches; erosion is only a problem for us, when there are structures at stake or loss of property.”
— Celie Dailey

Before the sand supply ceased about the end of the Pleistocene Ice Age, river sands “made it as far as the Alabama-Florida Panhandle and were incorporated into the barrier island coast” along the Gulf Coastal Plain. (3) With “very limited sand reserves” on the continental shelf, the west Florida “barrier islands depend for their existence largely on the reworking of their own sands and sand from associated tidal deltas.” (3)

The dunes at Cape San Blas are about 10-15 feet high, but the northern part of St. Joseph Peninsula has dunes generally about 20-30 feet high, with dunes “in excess of 50 feet in one area”. (6) According to the Duke University text: “Some sections of St. Joseph Peninsula have been nourished in the past, but the souther part, just north of Cape San Blas, has been eroding at rates up to 15 feet per year. The southernmost 3-mile portion of the cape is the most rapidly eroding shoreline in Florida, average 25 feet per year for the 150-year period of record…. The Cape San Blas lighthouse has been relocated six times!” (7)

On Cape San Blas, “the state and federal lands are undeveloped, but much of the remainder of the peninsula is developed with both single-family and multifamily dwellings,” according to the Duke University text. County wide, nearly 17 miles of “Gulf-front beaches on both St. Joseph and Indian Peninsulas” are eroding. Erosion is not a problem for beaches; erosion is only a problem for us, when there are structures at stake or loss of property. Hurricane Opal hit land near the St. Joseph Peninsula in 1995, crushing huge dunes, reshaping the coast and sweeping houses off their pilings. Though only a Category 3 storm and weakening when she hit, she brought flooding and storm surge of 20 feet. Opal was by no means a rare event. Not only is Cape San Blas vulnerable to hurricanes because it is a thin strip of sand, it is noted in the Duke University text that ”while all of Florida is subject to hurricanes, the Gulf coast has the higher frequency.”(2)

The maritime forest flourishes on secluded Cape San Blas. Shells are the main component of the wrack line on the beach. Foliage is whipped by the wind atop the stunning white dunes. Trees, shrubs, and saw palmettos grow in dense patches protected in dips between the hills of sand.

References:

  • (1) Living with Florida’s Atlantic Beaches: Coastal Hazards from Amelia Island to Key West (Living with the Shore), David M. Bush, et al., Durham, NC: Duke University Press, 2004, pg. 177.
  • (2) Living on the Edge of the Gulf: The West Florida and Alabama Coast (Living with the Shore), David M. Bush, et al., Durham, NC: Duke University Press, 2001, pg. 6.
  • (3) Living on the Edge of the Gulf: The West Florida and Alabama Coast (Living with the Shore), David M. Bush, et al., Durham, NC: Duke University Press, 2001, pg. 8.
  • (4) Living on the Edge of the Gulf: The West Florida and Alabama Coast (Living with the Shore), David M. Bush, et al., Durham, NC: Duke University Press, 2001, pg. 20.
  • (5) Living on the Edge of the Gulf: The West Florida and Alabama Coast (Living with the Shore), David M. Bush, et al., Durham, NC: Duke University Press, 2001, pg. 39.
  • (6) Living on the Edge of the Gulf: The West Florida and Alabama Coast (Living with the Shore), David M. Bush, et al., Durham, NC: Duke University Press, 2001, pg. 155.
  • (7) Living on the Edge of the Gulf: The West Florida and Alabama Coast (Living with the Shore), David M. Bush, et al., Durham, NC: Duke University Press, 2001, pg. 156.

Belinho Beach, NW Portugal: An Example of Rapid Beach Change; By H. Granja & J.L.S. Pinho

fig5

By H. Granja, CIIMAR, University of Porto/Department of Earth Sciences, University of Minho, Braga, Portugal and J.L.S. Pinho, CTAC/Department of Civil Engineering, University of Minho, Braga, Portugal;

Introduction

Portugal, located in the most western part of Europe, is a country with more than 900km of Atlantic coast. The coast is very diverse in terms of landforms and sediment types. Coastal zone topography ranges from high, shear rock cliffs (e.g., Sagres and Peniche areas) that are sometimes beachless, to low coastal plains that have long beaches as in the barrier Islands of the Algarve, and the long reaches along the N-S trending Atlantic coast. Small pocket beaches are typical of the rocky, highland shores. Beaches are backed by cliffs, bluffs, or sand dunes, and beach sediment ranges from sand size to gravels, pebbles, cobbles and boulders. Belinho Beach is part of a long beach stretch in NW Portugal that has transformed from sands to coarse gravels in just two to three decades.

“Besides exhibiting an erosion trend for decades, the NW coastal zone of Portugal was also the stage of a new phenomenon, since the end of 20th century.”
— H. Granja & J.L.S. Pinho

The NW coastal zone of Portugal (Fig. 1) is narrow, extending from the sea inland to an ancient sea cliff from a higher stand of past sea level. The coastal profile is composed of two main rocky platforms. The lower one extends offshore and under the lower beach. Until recently this seaward beachface was covered with sediment, but erosion has exposed the bedrock surface in recent time (Fig. 2) with resulting sand loss. The landward cliff and the associated higher platform are carved into faulted granites, while the lower platform, part of a NW-SE oriented complex syncline, is metamorphic Palaeozoic rocks. The surface of the lower platform is slightly irregular, with fault controlled low areas, overlain by a thin cover of Holocene sediments.

The hydrological climate of this coast is one of mixed energy, being both wave and tide-dominated.Tides are mesotidal (2 to 4m), semi-diurnal, with neap average tidal range of about 1m, and spring average tidal range of 2.8m. Maximum amplitude of tidal range can reach 3.9m. The wave climate is characterized by mean wave height of 2m, an average wave period of 9sec., and the main direction is from NW (79% of the time). The net sedimentary drift is from North to South, though at some points this is inverted due to the presence of outcrops, harbour jetties, or shoaling bars (as around the ebb tidal delta of the Cávado River mouth) that diffract the dominant NW incoming waves. The presence of some engineering structures (groins and revetments) also contributes to interference patterns in the general circulation and so on the morphology.

Changes in Beach Shape and Sediment Size

During the second half of the 20th century, coastal erosion in Portugal became a dominant process, as has happened in other coasts worldwide.

Besides exhibiting an erosion trend for decades, the NW coastal zone of Portugal was also the stage of a new phenomenon, since the end of 20th century. The usual impacts from erosion, with beach narrowing and thinning, cliff/bluff retreat and landward beach migration have been observed, but another striking change has occurred over a long stretch of beach. Between the Lima and Cávado Rivers (Fig. 1), previously dissipative, sandy beaches (Fig. 3) changed to mixed sand-gravel beaches with gravelly beach cusps by the end of the 1980’s (Fig. 4) and then progressively converted into entirely reflective gravel beaches after 2000, although maintaining the inherited dune systems in their backshores (Fig. 5). This change in both shape and the dominant sediment type of the beach developed from North to South, and has taken place very suddenly in terms of shoreline evolution. The new coastal landscape presents the exposed rocky abrasion platform, steep gravel beaches (with boulders, cobbles and pebbles, and, sometimes, small fine sand aprons), and dunes (composed of fine sand), inherited from the previous sandy-beach morphology (Fig. 5, see also Google Earth, Praia do Belinho).

The waves breaking at the base of the beach face expend all their remaining energy in the swash zone, favoring the development of a steep beachface aided by coarser sediments.

Is this change a recurrent event?

The present configuration and reflective state of Belinho Beach is thought to be analogous to another local feature that formed prior to the Little Ice Age (LIA). Gravel deposits (fossil beach ridges) now found beneath LIA dunes probably formed under the same conditions as the present gravel beach ridges (Fig. 6).

The abrupt switch of beach shape/sediment dynamics must be related to strong changes in sediment supply and/or wave energy. High energetic conditions can deplete sand sources, favoring the concentration of coarser sediments available from the inner shelf. This would be the case for the present as well as the pre-LIA beach. In contrast, the LIA beach would have been dominated by sand, the source for which was available during this period according to historical texts.

When sand starvation occurs, the beachface adjusts and switches to a state of inner-beach reflectivity and correspondent gravel ridge development at the high-water position. After a new influx of fine-grained sediment like sand, the dissipative conditions will be reestablished, but the gravel ridges will be buried and preserved under the new beach (Fig. 6).

At Belinho Beach, one of the gravel sources is the beach ridges under the LIA dunes, but another source is certainly the inner shelf itself (Fig. 7), which is being reworked under the present sea climate.

The present and future trend

Belinho Beach and its N-S continuation is a good example of a beach segment with a fast and extreme evolutionary trend. The change from a sandy state to a gravel state was reached in just a few years. And this change is not the temporary situation of sand stripping during winter storms and the exposure of an underlying cobble/boulder lag deposit; temporary seasonal changes of sediment size and beach type as documented elsewhere in the world, and sometimes referred to as summer and winter beaches. The present Belinho gravel beach is in a metastable state that is potentially likely to continue to change.

The presence of outcrops in the lower foreshore contributes to sediment accretion on the beach, making the seaward cross-shore sediment transport more difficult, which leads to an increase of the berm height and steepness of the beachface slope. The ridge (Fig. 5) defends the bluffs against a direct wave attack, and also allows greater infiltration of water from the swash, decreasing the backwash energy over the beach face. This contributes to a strong reduction of sediment movement offshore at the same time gravel ridges defend dunes.

“Belinho beach is an excellent example for coastal managers and decision makers to take the option of doing nothing (natural protection status) and to let nature take its course.”
— H. Granja & J.L.S. Pinho

The authors are conducting a monitoring program to study the ridge dynamics. This program comprises topographical surveys based on DGPS methodologies, sediment size analysis, and beachface cusp characterization using imaging processing tools.

During storms, the beach profile is smoothed with the destruction of the cusp morphology and pebble imbrication, while the build-up of the berm crest turns the profile steeper (Fig. 8).

Since the beach became fully reflective, volumetric changes are small. Erosive processes affect the beach only during storms, when partial foredune overwashing occurs.

The small difference between the maximal and minimal sediment volumes in this sector indicates that the beach keeps some stability in its profile and sediment size, i.e. the beach is metastable. Consequently, the beach presents a robust behaviour, being less vulnerable to storm surge flooding and other coastal hazards; at least temporarily.

This coastal segment is undeveloped (just agricultural fields behind the dunes) and has large rock outcrop areas in the intertidal and subtidal zones, a steep beachface, a robust gravel ridge parallel to the foredune, and a well-developed dune system. And because of its short-term history of rapid change and metastable state, Belinho beach is an excellent example for coastal managers and decision makers to take the option of doing nothing (natural protection status) and to let nature take its course.

A Tale of Two Beaches: Tompire Bay, NE Trinidad; By John Weber, William Neal & Jeanette Arkle

Fig.-9-scarped-upper-beach-and-sargassum

By John C. Weber and William J. Neal, Department of Geology, Grand Valley State University, Allendale, MI, and Jeanette C. Arkle, Department of Geology, University of Cincinnati, Cincinnati, OH;

Trinidad, West Indies, has many beautiful beaches (IMA, 2013), and among the most interesting are those of the Northern Trinidad coast. Along the coast an east-west range of mountains, the Northern Range, emerges from the sea to peaks over 900 m in elevation (Fig. 1).

The shoreline of sea cliffs and rocky headlands is punctuated by both pocket beaches and short linear beaches associated with small river mouths. Tompire Beach, a particularly spectacular linear beach, is located along the northeast coast, near the village of Redhead (Cumana), off of Toco Main Road (Fig. 1, inset).

Tompire Beach, and the uniqueness of the geology of the Northern Range, have drawn the senior author to this location several times over the last 25 years. Here, an ancient beach has been uplifted out of the sea and is now perched ~20 m above the modern sands of Tompire Beach(Fig. 2).The preservation of this feature presents a unique opportunity to compare factors that shape the beach and, in turn, how an ancient beach can serve as direct markers for dynamic change.

“The “two beaches” provide an opportunity to compare the modern and ancient deposits.”
— J.Weber, W.Neal & J.Arkle

Two Beaches: Modern & Ancient

The present beach is a gentle arcuate strip extending north from Pt. Playa to another rock headland, a little over 0.8 km in length with the mouth of the Tompire River located about midway along the beach. At the mouth of the Tompire River the beach forms a spit-like emergent sand bar across the river mouth (Fig. 3).

The river mouth is sometimes closed in the dry season, but then breaks through to form its ocean outlet in the wet season. During storms the barrier bar is overwashed by waves and beach sand is transported across the bar into the lagoon.

The rugged shoreline has evolved under the influence of several factors. The spectacular rock structures exposed in the sea cliffs attest to ancient mountain building, and uplift in more recent time. The latter resulted in the raised marine terrace, capped by the fossil beach. This wave-cut platform stands about 20 m (>65 ft) above the present beach and modern-day sea level (Figs. 2 and 4), and has been cultivated for copra (dried coconut) production. The “two beaches” provide an opportunity to compare the modern and ancient deposits. For example, the internal structures (e.g., laminae and bedding) are similar (Figs. 5 and 6).

Modern Tompire Beach is a pebbly to coarse sandy beach, with abundant metamorphic rock fragments. Generally, the pebbles with abundant quartz veins are the ones that survive the vigorous attack by the strong Atlantic waves. The ancient beach is of similar composition, differing mainly in the sediments’ brown color due to staining by groundwater (Figs. 2 and 6). This ancient beach deposit has been recently dated at about 30,000 years old, using OSL (optically stimulated luminescence) (Arkle et al., 2015).

Modern Beach Sculptors

On a regional scale, imagine the island of Trinidad rolling on a north-south axis with the western side sinking and the eastern side rising. In a broad sense, western Trinidad is submergent, while the eastern side is emergent. The western coast of Trinidad is heavily embayed, characterized, in part, by extensive shorelines of mangrove swamps, and fewer beaches. The climate is dryer, less windy, and faces the Caribbean Sea and Gulf of Paria; areas of lower wave energy. The submergent pattern is also apparent along the north coast where pocket beaches become more pronounced and abundant to the west where tectonic sinking is greater (Fig. 1). Technically, this relative sinking versus rising is related to Plate Tectonics, driven by right-lateral transform tectonics at a pull-apart step-over, and/or over a deep lithospheric tear that is propagating eastward (Weber et al. 2010).

A second factor in the shaping of the emergent northeastern shore is that the eastern end of the Northern Range faces head-on into the strong easterly trade winds which generate an almost constant swell which, together with storms, generates a high-energy wave regime from the western Atlantic Ocean. Although the tidal range is not great, many of the narrow beaches are submerged at high tide, and waves are a dominant erosional force. This setting also results in a different climate than that of the western parts of the island. The annual rain fall (~5 m/yr) is much higher, and the land is covered in dense and lush tropical vegetation. The higher runoff is reflected in small rivers and streams coming down to the shore, and usually marked by somewhat more robust beach development. Local geology also is a factor in that the folded rocks of varied composition erode at different rates, producing an irregular shoreline of varied elevation. Tompire Bay’s beach is an example of the latter (Fig. 7).

Leatherback Sea Turtles & Sargassum Wrack

The northeast coast of Trinidad, including Tompire Bay, is a nesting ground for endangered leatherback sea turtles (Dermochelys coriacea). Programs instituted some years ago appear to be working as there has been a resurgence in the number of nesting turtles in the last few years. During nesting season Tompire Beach is patrolled at night for nest protection.

In 2011, unusual, thick accumulations of Sargassum seaweed on the beaches in the Eastern Caribbean were noted, and again in 2014. (See “Why is so much brown seaweed washing ashore?” Guardian and “A different look at Sargassum seaweed;” The Trinidad Express).

“The width of the continuous Sargassum wrack line, and its thickness (up to 2 m+) interfered with the turtles’ access to the beach.”
— J.Weber, W.Neal & J.Arkle

These massive amounts of seaweed are thought to be occurring because the range of areas in which the plant grows has increased, and is now growing where it can be picked up by currents in the western Atlantic and eastern Caribbean and carried to these islands. There is a preliminary suggestion that the change may be due to global warming which is a strong possibility as Sargassum needs nutrients and high water temperatures. Perhaps warming of the tropical ocean is changing habitats.

During the summer of 2015, large amounts of the seaweed were accumulating on Tompire Beach as massive wrack lines (Figs. 8, 9, and 10). Wrack lines are common on this beach, and the accumulations of drift wood at the back of the beach attest to the highest levels reached by storm waves (Fig. 8), however, the massive amounts of seaweed is a new phenomenon. The width of the continuous Sargassum wrack line, and its thickness (up to 2 m+) interfered with the turtles’ access to the beach. (Figs. 9 and 10) The sea turtles were forced to travel and nest up river on its sandy banks and on the back side of the barrier bar (Fig. 11).

Ancient Processes & Archives: Emergence of a Mountain Range

The back-beach sea cliff has some of the best rock exposures in the region, kept bare by wave action and mass wasting (Figs. 7 and 12). The spectacular folds (anticlines and synclines) are obvious even to the non-geologist. Three generations of folds and faults have been documented and studied in detail by Weber and Ferrill (2002). The dominant rock types are meta-sedimentary slates and meta-sandstones. These rocks have Mesozoic depositional ages and Cenozoic metamorphic ages (Weber et al. 2001). The composition of the present quarzites and slates, cut by veins of quartz, reflect the original sedimentary rocks that were shales and quartz sandstones. These rocks are the immediate sources for the beach sediment (Figs. 5 and 12), as well as material flushed down the Tompire River.

Lessons from the Two Beaches

The unique juxtaposition of a modern beach and the preservation of it’s older counterpart perched above, not only make for a beautiful remote setting, but retains an archive of the dynamic environment that shaped them both. Change is the rule, yet the physical conditions that shaped the two beaches are similar. The mountains evolved, the beaches have evolved. Natural change is the rule. But like the turtles, we must cope with such change without altering the natural habitat.


References

  • Arkle, J.C., Owen, L.A., Weber, J., Moonan, M., and Enkelmann, E., 2015, Late Neogene-Recent Evolution of the Northern Range, Trinidad, presented at 2015 Meeting, Caribbean Geological Conference, Port of Spain, Trinidad, 17-21 May.
  • Institute of Marine Affairs, 2013, A Guide to the Beaches and Bays of Trinidad and Tobago: Institute of Marine Affairs, Chaguaramus, Trinidad, West Indies, 113p.
  • Weber, J., Saleh, J., Balkaransingh, S., Dixon, T., Ambeh, W., Leong, T., Rodriguez, A., and Miller, K., 2011, Triangulation-to-GPS and GPS-to-GPS geodesy in Trinidad, West Indies: Neotectonics, seismic risk, and geologic implications, Journal Petroleum and Marine Geology, v.28, p.200-211, doi:10.1016/j.marpetgeo.2009.07.010.
  • Weber, J.C. and Ferrill, D., 2002, Structural geology of the Tompire Bay outcrops, eastern Northern Range, Trinidad, in, Jackson, T. A. (Ed.), Caribbean Geology Into the Third Millennium, 87-95, UWI Press.
  • Weber, J.C., Dixon, T.H., DeMets, C., Ambeh, W. B., Jansma, P., Mattioli, G., Saleh, J., Sella, G., Bilham, R., and Perez, O., 2010, GPS Estimate of relative motion between the Caribbean and South American plates, and geologic implications for Trinidad and Venezuela, Geology, 29, 75-78.
  • Weber, J.C., Ferrill, D., and Roden-Tice, M., 2001, Calcite and quartz microstructural geothermometry of low-grade metasedimentary rocks, Northern Range, Trinidad, Journal of Structural Geology, 23, 93-112.