The Problems with Coastal Erosion.

Olivia Peters

December 9, 2013

The Problems with Coastal Erosion.

When you go to the beach, what do you see? The obvious things are white sandy coastlines, crystal clear water, tons of people playing around, and even some animals, such as fish and birds. However, there is a problem many do not see. More than 75 percent of the world’s beaches are suffering from coastal erosion. “Coastal erosion is the process of wearing away material from a coastal profile due to imbalance in the supply and export of material from a certain section.” (Marchland. 2007) Coastal erosion can be caused by numerous things but is mainly influenced by hurricanes, transport gradients, loss of sand, protruding areas, marine deposit shorelines, downstream erosion, sea level rise, subsidence, and natural variance. Coastal erosion is not an occurrence limited to the United States. States such as Massachusetts, Florida, and Rhode Island are certainly affected, but so are North and West Africa, the United Kingdom, England, and Indonesia. Because most homes and property are located on coastlines, humans have taken many measures to control coastal erosion. These include beach nourishment, bulkheads, groynes, geotextile tubes, and gabions. Coastal erosion doesn’t just affect our homes though. Marine life, such as sea turtles and grunion are also suffering. The world’s economy is also being affected. Because of coastal erosion, fewer people are traveling to coastal towns, and that is directly impacting their tourism-related economies.  Unfortunately, man-made interventions to coastal erosion often present more problems than they were initially thought to solve.

In order to understand the coastal erosion process, you must distinguish the factors that interact with each other along the shoreline. On a geological time scale, coastal evolution in sedimentary environments is dictated by the supply and demand of the sediments. The supply is determined by the availability of the sand and the transport ability of water and wind. The demand of the coast is determined by the rate of sea level rise and the geology of the coastal plain. As stated previously, coastal erosion is the process of wearing away material from a coastal plain due to the imbalance in the supply and export of material from a certain section. “It takes place in the form of scouring in the foot of the cliffs or dunes or at the subtidal foreshore. Coastal erosion takes place mainly during strong winds, high waves and high tides and storm surge conditions, and results in coastline retreat and loss of land.” (Marchland. 2007.) Coastal erosion become a problem when there is no room to harbor change.

Sandy beaches provide a natural barrier between ocean and land, but because the sand is so lightweight and weak, the beaches change and move through the actions of waves, winds, and currents. There are many causes of beach erosion. Some are hurricanes, transport gradients, loss of sand, protruding areas, marine deposit shorelines, downstream erosion, sea level rise, subsidence, and natural variance. When a hurricane comes in, especially one with speeds up to or exceeding 111 miles per hour, it changes the component of the beach; the beach is thrown into total chaos (Sallenger.) Dunes are the first defense mechanism against storms on the beach. Because we place so many structures on the beachfront, the dunes are weakened, making them less resilient. When a normal storm comes, the beaches reform themselves to accommodate the change in atmosphere. When a hurricane, tsunami, or typhoon arrives, with speeds doubling those of a regular storm, the beaches are unable to cope.

Transport gradients increase erosion by moving the gradients in the direction of the net transport. This can be due to gradients in the wave conditions at certain stretches, particular bathymetric conditions, or a curved coastline.

Loss of sand, while seeming redundant, is also a major contributor to coastal erosion. Breaching and over washing is the loss of sand inland due to “failure of the beach head allowing flooding by tidal action.” (Marine Biodiversity Wiki. 2008.) The coast also loses copious amounts of sand during extreme storm surge and wave conditions. The storm surges cause offshore movement of sand due to an unbalanced equilibrium in the coast’s geology. The strong waves cause the sand bars to move towards the sea. Also, if there is a canyon close to a transport coastline, sand may travel into the canyon and be lost from the beach.

Coastal erosion also occurs when material is lost from a protruding area. It mostly happens when sandstone headlands at the tip of deltas do not receive enough material from the river due to natural shifting of river alignment.

Erosion is also caused when marine deposits are suspended between sections of semi-hard protruding coastlines. The shape of these shorelines is dependent on the presence of semi-hard sections and wave climate.

Beach erosion also occurs downstream of accumulative forms. Along a coastline with oblique wave approaches, the tendency is for the sand spit formation to travel parallel to the coast. The sand shifts offshore, which causes the downstream coastline to erode.

As global sea levels rise, erosion increases. “An increasing sea level will cause shoreline setback, which is approximately equal to the sea level rise divided by the slope of the active coastal profile, when considering equilibrium profiles. (Marine Biodiversity Wiki. 2008.)”

Subsidence is another cause of beach erosion. Subsidence lowers the surface of the sand. It can be caused by natural measures such as the settling of soft sediments, tectonic activity, or it can be caused by humans when we engage in invasive occupations such as drilling for oil or populating the coast with structures. Subsidence acts the same way as sea level rise. Unlike sea level rise, however, which is a gradual and slow process, subsidence may occur rapidly.

Natural variation in the supply of sand can also cause coastal erosion. Droughts in river basins can result in long periods of decreasing sand on the shore (Marine Biodiversity Wiki. 2008.)

With beach erosion quickly becoming a dangerous consequence of life on earth, people have been studying it and searching for a way to prevent it. Some preventative measures include beach renourishment, bulkheads (also known as retaining walls), groynes, geotextile tubes, and gabions.

“Beach renourishment is the process of dumping or pumping sand from elsewhere onto an eroding shoreline to create a new beach or to widen the existing beach.” While renourishment doesn’t stop erosion, it slows down the process. The waves erode the nourished sand instead of houses or roads. Renourishment is often suggested when beach erosion threatens to remove an existing beach and potentially harm the property beyond it. The renourishment process will only function if it is publicly funded, as it is somewhat costly and will need to be replaced. There are many advantages with renourishment. It widens and restores recreational beaches, the structures behind the beach are protected, and it is a lot safer than other methods like bulkheads and gabions in that there are no permanent hazards left on the beach or within surf zone. There are some drawbacks, though. Beach nourishment sand actually erodes faster than the natural sand. It is also very expensive, usually costing a few million dollars. Because it has to be replenished, the price can escalate up to over 100 million dollars. Nourishment turns the beach into a construction zone, making it unable to be used. The sand added to the beach is almost always different from the original sand and because of the difference, it can change the surf conditions and bars on the beach. The most detrimental consequence of nourishment is the nourished sand can damage and hurt marine life and the beach itself. The bulldozers carrying the sand can crush organisms, the sand can bury marine life, it can change the shape of the beach, and even make the water too muddy. This can harm the habitats of organisms such as plants, insects, turtles, and birds. (Beach Nourishment Basics)

Bulkheads are also a common practice for controlling beach erosion. Most commonly referred to as an armoring wall, a bulkhead is a manmade structure constructed along shorelines that acts as a barrier against waves. These walls actually cause more damages to the beaches, though. When waves reflect off the bulkheads, they scour away sediments and cause the erosion to increase. When long stretches of beach are lined with bulkheads, the beaches that are composed of fine sediments can erode to just gravel within a few decades. Bulkheads also shut off the supply of sand and gravel to the beach, causing the beach to lose its finer sediments. When bulkheads are built, overhanging shrubs and trees are often removed. This can endanger marine life, reduce organic matter, and increase siltation. It also reduces shade and shelter along the beach, reducing the spawning habitat (Schlender.)

A groyne is another popular way to control beach erosion. “A groyne is an active structure extending from shore into sea.” It catches and traps parts of sediment that are moving into the surf zone. Groynes are frequently used, however, they do have unfavorable effects. Because the protection of only one groyne is insignificant, they are usually designed in groups. Between the groynes, large masses of water accumulate, causing erosion of the seabed (Pruzak.)

“The geotextile tube technology is mainly used for flood and water control, but they are also used to prevent beach erosion, and for shore protection and environmental applications.” Because these tubes are cost effective and easy to install, they are good alternatives to hydraulic and coastal structures. They are most commonly used with a barrier and are placed under the wall to help stabilize it (Shin. 2007.)

Gabions are another alternative to controlling beach erosion. They are wire mesh baskets filled with crushed rock. However they are flexible, they can absorb partial wave and wind energy, reducing scouring problems. However, they are not durable enough to withstand regular direct wave action, so they are restricted to the upper part of the beaches. This placement provides protection from backshore erosion. Gabions need to be repaired often to make them viable to make them something more than just a short term solution. They can also become dangerous if not properly repaired. If the cobbles (crushed rock) are released from a broken gabion, then it can accelerate damage to local baskets. They also disrupt the natural landform, modify dune habitats, and can result in dune face scour at the ends (Brampton, Motyka, Coates. 2000.)

Because coastal erosion is such a widespread problem, people all over the world are affected by it. In the United Sates, coastal erosion affects, but is not limited to, Massachusetts, Florida, and Rhode Island. It also affects other countries such as, North and West Africa, Norfolk, Suffolk, England, and Indonesia.

Massachusetts is becoming a major erosion zone. The southwest shore of Nantucket is eroding at a rate of 10 to 12 feet per year. We begin to grasp the scope of what 10 to 12 feet per year looks like when comparing it to Humarock Beach, which had an erosion rate of only two feet per year in 1950 to 1998. In Massachusetts’ case though, long term erosion is not the sole issue. For instance, Springhill beach in Sandwich has huge episodic, storm-induced erosion, which results in major losses of homes near the shore (Focal Points. 2001).

In cases like Florida, you may have a beautiful beachfront property but no beach. Most of the soil in Florida is a sand and limestone mixture. Because these materials are not compact, they easily erode. Out of the 1,240 kilometers of beach, approximately 195 kilometers have already been eroded. Florida’s dunes are the only major defense against storms because they act as a barrier between the storm waves and coastal development. Even with these natural barriers, the coast has still undergone massive coastal erosion. This has resulted in narrowing beaches that are uninhabitable for public use. In 1992, reports produced by the Florida Department of Natural Resources classified 65 percent of west Florida beaches as “critical erosion areas.” Because of this, many beaches have established nourishment projects. In 1992, Congress instructed the U.S. Geological Survey (USGS) to participate in a 5-year study of west coast Florida’s barrier island. This was to help them understand the geological history of the barrier island, specifically the process of carrying sediments on the inner shelf. The west coast barrier island sits near a gentle sloping carbonate platform. Its bottom consists of a limestone bedrock, with quartz and carbonate lying on top. Limestone is an easily erodible sediment. The USGS also discovered that the sediments aren’t evenly distributed along the continental shelf. There are only certain areas of an adequate thickness to withstand or resist erosion while the less populated sediments are more prone to erosion (U.S. Department of the Interior).

In 1938, Sakonnet Point was the most seaward point in Rhode Island, hosting large sand dunes that stood up to 4.6 meters high. Today, they are almost completely submerged under a high tide due to major storms and sea level rise (Coastal Erosion).

In the northwest coast of Africa, the average rate of erosion is between one to two meters per year. Locally, however, rates of up to hundreds of meters per year have been observed, especially when man is trying to prevent it. In West Africa, erosion has been strikingly detrimental to their living. They have problems with salinization of water and soil, depletion of ecosystems, and massive flooding. This has been adverse to their gross domestic product, since most of their income comes from fishing, tourism, and commerce (Barbiere. 2012).

Happisburg in Norfolk, is on the coast of the North Sea. It was small village, home to about 600 houses, and was actually quite a distance from the sea. Records show that over 250 meters of land were eroded between 1600 and 1850. The town is mainly affected by massive flooding, which accounts for most of its eroding. Coastal erosion prevention has been put into place, and even succeeded in controlling the problem, but is now in need of repair because it is no longer performing its job correctly. This town’s tourism rate is directly affected by its beaches, and because these beaches are eroding, tourism has significantly dropped (Coastal Erosion at Happisburg, Norfolk).

“The Suffolk coastline of East Anglia has been eroding for 1000's of years and suffers rapid and frequent change- the changes are due to the coastal process of erosion and deposition and the large scale movement of material down the coast by longshore drift.” Dunwich is a small village on the coast of Suffolk. While once a thriving port, storms, floods, and coastal erosion have almost destroyed the little town. Its coastlines are made up of soft rock (a mixture of sand, gravel, and clay) that make it highly erodible. It also suffers from a narrow beach, and its cliff faces are greatly affected by weathering. In 1990, seven meters were demolished over just a few days by a storm that hit the coast. Dunwich is one of the most extreme examples of how coastal erosion can affect a town (Chambers. 2007).

The Holderness coastline on the east coast of England, near the Humber Estuary, is the “fastest eroding” coastline in Europe because of its soft clay cliffs and strong waves. In this case, artificial measures to try and keep the erosion at bay have only sped up the process because they starve the beach of its sand making it more vulnerable (SA.)

Indonesia also battles coastal erosion. Denpasar City has lost 62 percent of its shorelines in the last 20 years. That is equivalent to 10 of its 16 kilometers of shoreline. Along with Granyar Regency, their population’s main sources of income are primarily dependent on their exotic beaches. These destinations are quite attractive to the rich Indonesians that want beachfront properties to avoid the chaos of inner city life (Suriyani. 2010.)

Not only does beach erosion affect our homes and lives, it also has a direct correlation to sea turtle population. It is not just the erosion that affects the turtles. Another major contributor to the sea turtle problem is our man-made structural attempts to prevent the coastal erosion. “What many do not realize is that these man-made structures prevent sea turtles from continuing their innate life cycles.” The construction of sea walls, for instance, interferes with sea turtle nesting because they change the shape of the beach. These coastal structures threaten sea turtles by reducing nesting habitat locations and forcing them to nest in dangerous areas. “Although armoring is intended to decrease sand erosion and, therefore protect the beach, studies show that areas protected by armoring are more likely to create more severe erosion by interrupting natural sand shifts.” So while our human habitats are being protected, the sea turtles’ are not. Studies have proven that fewer turtles crawl onto beaches with beach erosion protection, and the fewer turtles that do crawl near the sea walls often return to the water without nesting. This is known as a false crawl. Because they do not nest, the sea turtle population decreases. Beach nourishment also causes a huge problem with sea turtle nesting. Because the nourished sand has a different consistency than natural beaches, the beach becomes unsuitable for nesting. The nourished sand is unusable because it is too compact for animals to nest in (Information about Sea Turtles: Threats from Coastal Armoring. 2013).

            Grunion are another example of marine life affected by coastal erosion. Grunion spawning occurs from March through August, with it peaking in May. They leave the water and spawn on the beaches. For four nights, beginning on full moons, spawning occurs after high tides and last for several hours. The female has to twist her body and dig into the sand until she is half buried. She then deposits her eggs, and then the male comes to release his milt. When coastal erosion prevention happens, such as armoring walls or nourishment, it increases the difficulty for the grunion to spawn. The armoring walls prevent the fish from finding the perfect location, and the nourishment makes it almost impossible for the females to dig their holes because the sand is too compact, just like with the sea turtles. In the rare occurrence that the eggs are released, and the eggs hatch, the nourished sand makes it harder for the newly hatched grunion to swim back to the ocean (California Grunion Facts and Runs).

            Because most of the population of this world lives on some sort of coastline, beach erosion plays a huge part in how we live. Not only does it affect our homes, but it effects our economic status and way of life as well. In the United States alone, approximately 350,000 structures are located within 500 feet of coastline. Most likely, about 87,000 of these structures will erode into the ocean or Great Lakes in the next 60 years. Based on current coastal property loss estimates, during this period, coastal property owners will pay an average of 530 million dollars per year in erosion related damages (Focal Points. 2001).That’s almost 32 billion dollars just in erosion related damages. In addition to that, the Federal Government spends about 150 million dollars every year on shoreline erosion control, just as beach renourishment. A Heinz Center study discovered that erosion may claim one out of every four houses that lie within 500 feet of the shoreline by 2050 (Rabenold. 2013.)

In Ghana, spending money on beach erosion prevention would be costly, but it would actually strengthen the economy. Since most of Ghana’s income comes from tourism, industry, and fishing, fixing the erosion problem would improve these sources of income. The beaches would be more populated because they would be in better condition, and the fishing would be better because the fish could go back to their semi natural habitat (Sea Defense and Erosion Project, Ghana).    

            Texas has some of the highest beach erosion rates in the country. 64 percent of the Texas coast is eroding at an average rate of six feet per year while some locations lose up to 30 feet per year. Because of this erosion, Texas property values decrease, tourism suffers, homes are sometimes lost, and the local economies suffer the consequences (Pinchback).

            California also has beach erosion problems that affect its economy. Since California is mainly coast, their tourist traffic is always high. According to an economic analysis performed by California Research Bureau for the Resource Agency, California’s tourism contributed 9.9 billion dollars to the state’s economy in 1992. In 1995, the California Department of Boating and Waterways estimated that Californians spent 3.4 billion dollars on day trips to the beach in a single year (http://resources.ca.gov/ocean/97Agenda/Chap5Erosion.html). Tourism rates, however, have fallen due to the recent coastal erosion problems. This is because the eroded beaches are almost always under construction. The unsightly armoring walls and gabions scattering the beaches detract from a peaceful vacation.

            While initially proposing to prevent and correct shoreline erosion, the reality is that the solutions cause more problems. As the examples have shown, every nation that has employed interventions for coastal erosion ended up hastening the coastal erosion process, encroaching on nature, and thereby further endangering their own economies. In light of what I have discovered in preparing this paper, I find it to be the best interest of nature and man to allow the coastal erosion process take its natural course.  

“When He established the heavens, I was there,
When He inscribed a circle on the face of the deep,
When He made firm the skies above,
When the springs of the deep became fixed,
 When He set for the sea its boundary
So that the water would not transgress His command,
When He marked out the foundations of the earth;
Then I was beside Him, as a master workman;
And I was daily His delight,
Rejoicing always before Him,” (Proverbs 8:27-30)

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