History of Eastern United States Coast Barrier Islands - Research Paper Example

History of Eastern United States Coast Barrier Islands Abstract Barrier islands are important features of the coastal areas and they have served the purpose of protecting the coastal shoreline from hurricanes and other storms. Their formation results from the rising sea levels and their survival and existence are dependent on the hurricanes, waves and other storms. The eastern United States Coast barrier islands are important since they are the largest in the world and have undergone significant changes in the past years. The Native Americans first occupied these barrier islands. They were later taken over by the European settlers for their recreational and touristic pursuits. However, they have diminished in size and retreated in the past years due to rising sea level, diminishing sediment, storms, and human interference. Extensive human settlement in these areas has raised concerns regarding the loss of habitat. Although vulnerable, these barrier islands are very important economically, serving as areas for tourist development, source of food, and employment. (Key words: barrier islands, rising sea level, storms) Table of Contents Abstract 1 Table of Contents 2 Barrier Islands 3 Types of Barrier Systems 4 Formation of Barrier Islands 6 The Historical Changes in the Mississippi-Alabama Barrier Islands 8 Retreating and Diminishing In Size of the Gulf Coast Barrier Islands 9 Activities on Eastern United States Coast Barrier Islands 10 The Importance of the Eastern United States Coast Barrier Islands 12 References 14 History of Eastern United States Coast Barrier Islands Barrier Islands Barrier islands are defined as thin linear mobile strips of sand measuring up to around 10 – 15 metres (30 – 50 feet) above the sea level. They usually create chains situated a number of miles offshore alongside the many passive margins. The backbarrier region separates the barrier island from the mainland and shallow bays, marshes, estuaries, or lagoons usually occupy it. Barriers are created by the vertical accumulation of the sand from wind and waves action. Barrier islands are called so because they signify the shoreline natural protection from the forces of tsunamis, tides, currents, and waves from the core ocean. However, majority of the barrier islands have been turned into resort-type living and beautiful beaches (Kusky 2008, 5). The development of the barrier islands characterizes one of the most dangerous trends in the coastal zones. This is because barriers are juts mobile strips of sand moving in response to the changing storms, tides, coastal currents, and sea levels. Storms are able to move the complete sandy substrate out from the underneath of the tall buildings. Kusky (2008, 6) states that “the size of barrier islands ranges from narrow and discontinuous strips of sand that may be only a few hundred feet wide, to large islands that extend many miles across and also in length.” The length and the width are calculated from the existing amount of sediment and the balance between the tidal and wave energy. Majority of the barriers are built from sand (sand from the eroded coastal cliffs, deposited by rivers along the delta systems or sand left from the glaciations). Barrier islands are supposed to be discontinuous to permit water from the tidal changes to get back to the sea along the tidal inlets systems (Kusky 2008, 6). The sub environments of barrier islands are classified the same as those of beaches. These sub environments include barrier interior, landward interior, and the beach. The beachface of the barrier is the most vibrant section of the island. It absorbs energy from the tides and waves and responds much like the mainland beaches. The beach backside of many barrier islands are marked by a foredune ridge or a long frontal, followed landward by the secondary dunes. In the United States (U.S.), the Gulf of Mexico and the eastern seaboard demonstrate the greatest advancement of the barrier island system. Regions with low tidal variations in low to middle climate zones are the most widely developed barrier systems (Kusky 2008, 7). Examples of well-known barrier islands include the Outer Banks of North Carolina, Padre Island of Texas, and Cape Cod of Massachusetts (Nichols and Williams 2008). Types of Barrier Systems There are several types of barrier systems. Barrier spits join the mainland on one end and end in the open ocean or in a bay on the other end. This type of barrier system is common along the active tectonic coasts (Kusky 2008, 7). Cape Cod, Massachusetts is an example of a spit created along the passive continental margin. Another example is the South Carolina barrier spit as shown in figure 1 (Watson 1997). Some of the spits possess ridges of sand that curve about the end of the spit that ends in the sea, thus, reflecting their growth. These types of spits are referred to as recurved spits. An example of a recurved spit is the Sandy Hook located at the northern end of New Jersey coast. Spits that form as longshore currents take sediment along the coastline, and the coastline forms a bend into the bay. In most cases, the currents that take the sand go straight, and take the sediment offshore, leaving it in a spit that projects out from the bay’s mouth. There are other subcategories of spits and they are categorized on the basis of their shapes. For instance, spits known as tombolos connect the offshore islands with mainland, while others possess cuspate forms or they project outward into the open waters (Kusky 2008, 8). Figure 1: South Carolina barrier spit. Source: Watson, J. M. “South Carolina Barrier Spit.” USGS. November 9, 1997. http://pubs.usgs.gov/circ/c1075/barrier.html. In some of the cases, the barriers may grow completely across the bay and block off the water inside the bay from accessing the ocean. These forms of barriers are referred to as the welded barriers and they are common along the rocky coasts of Alaska and England. Welded barriers seem to form where tidal energy is very low and this prevents tides from forming tidal channels that permit salty water to flow into the bay. Most of the welded barriers tend to be filled with freshwater or they are brackish because they are blocked from the ocean. Barriers form by various mechanisms in different settings and the most common mechanisms are the accretion and growth of spits that breach during storms, submergence of previous islands when the sea level rises, and the development as offshore sand bars. Barriers move constantly and they respond to waves, sea-level rise, currents, and storms by varying their shape and position. Barriers that move onshore are referred to as retrograding barriers, and they move by the rolling over process (sand on the outer beachface is carried to backshore and overrun by the subsequent sand from the beachface). The continuation of this development makes the barrier to roll over by as it moves onshore (Kusky 2008, 8). Formation of Barrier Islands Barrier islands develop from the rising sea levels. Thus, they have been common landform during the period of ice age as the sea repeatedly retreated and advanced across the coastal plains. The subtle and narrow sand ridges commonly found on North Carolina lower coastal plains are former barrier islands stranded when the level of the sea withdrew some years ago. Most of the coastal communities such as the Beaufort, Morehead City, and the Harkers Island occupy land that was one time islands (these islands are approximately aged 120,000 years). Neal, Pilkey and Orrin (2004, 60) indicates that the early settlers in the regions made use of the safety given by the comparative high elevations of the barrier islands. As the level of the sea began to rise (close to 18,000 years ago), they flooded the previous river valleys forming estuaries and thus causing the previously uncomplicated and straight shorelines to become irregular. The ridges between the previous river valleys then developed into headlands that jutted out into the ocean, causing them to become vulnerable to wave attack. As the waves covered the headlands, the longshore currents spread the eroded sands either downcoast or upcoast, creating spits that moved across the estuaries mouth. On the other hand, wind collected large sand dunes at the back of the beaches creating ridges that were parallel to the shore. Thus, the sand-ridge-covered spits become spits due to two forces (flooding and storms). An example of such island formation is the Currituck Peninsula. In the last few centuries, 26 different inlets have cut the spit that lengthens south out of Virginia (Neal, Pilkey, and Orrin 2004, 60). Most of the barriers (Horn Island [Mississippi], Sanibel Island [in Florida], and Galveston Island [in Texas]) were initially “migrating across the continental shelf and then began to grow seaward when the rise in sea level slowed about 5,000 years ago” (Morton 2008, 18). Some of the barriers have grown factually, as spits linked to the mainland shore (such as Bolivar Peninsula [in Texas] and St. Joseph Peninsula [in Florida]). Other barriers were created around an island main of the former barrier deposits left over from the previous time the sea level was almost the same level as it is today (Morgan Peninsula and east Dauphin Island of Alabama). Barriers such as Anclote Key of Florida and Mississippi Sound barriers might have emerged from the offshore sand shoals (Morton 2008, 18). Presently, the largest sand dunes and highest barrier elevations are found on the seaward building (progradational) and the sand-rich upward building (aggradational) barrier islands such as the St. Joseph Peninsula, Florida; east Dauphin Island, Alabama; and Central Padre Island, Texas. Most of the coast sand that was carried ashore as the sea level attained its present position is accumulated in the early mentioned high profile barriers. The abundant sand makes these barriers to have low erosion rates. Landward retreating and migrating barriers such as the South Padre Island, Texas; Chandeleur Islands, Louisiana; and St. George Island, Florida usually have high erosion rates due to their location. They are usually located away from the main sources of sand (Morton 2008, 18). The map below shows the Barrier Islands found in the Gulf of Mexico. Barrier Islands found in the Gulf of Mexico. The Historical Changes in the Mississippi-Alabama Barrier Islands The Mississippi-Alabama islands are very dynamic and the intensity of their movement is so great that the changes in their land areas and positions have been the focus of scientific investigations for many years. A number of regional studies have dealt with the changes in the shoreline location of the offshore islands. For instance, a study done by Waller and Malbrough in 1976 indicated changes in the rate of shoreline that transects the islands and the sequential rates and magnitude of downdrift island accretion and updrift island erosion. In 1983, Shabica et al. reported changes in the rate of gulf shoreline between the years 1957 and 1980 and barrier islands overwash-penetration distances (Morton 2008, 1588). In 2008, Otvos and Carter offered a comprehensive account of the storm-related morphological shifts along the Mississippi-Alabama barrier island strip (Morton 2008, 1589). Retreating and Diminishing In Size of the Gulf Coast Barrier Islands Shoreline retreat is already occurring along the majority of the world’s coast. For instance, retreat rate at the barrier ocean shorelines located on the eastern coast of U.S. ranged from two to 4 feet per year (Pilkey and Young 2009, 53). Most of the Gulf Coast barrier islands are decreasing and retreating in size. For instance, the Chandeleur Islands lost approximately 85 percent of the surface region during the Hurricane Katrina. The Chandeleur Islands serve as the first line hurricane defense for the New Orleans region. It is important to note that as the mainland shorelines and the barrier islands submerge and erode, onshore facilities in the low-lying coasts regions are rendered susceptible to destruction and inundation (Gray 2009, 196). There are expectations that the barrier islands and spits will experience increased overwash (a mechanism in which some of the barriers migrate landward) and erosion (Jones and Philips 2011, 167). The change will possibly be dynamic; “erosion at one site may lead to deposition further along the beach due to longshore transports” (Jones and Philips 2011, 168). It is possible that at some level that the threshold will be attained and the features will be considerably removed or diminished in size. Studies show that barriers have reduced in size in some regions in the last century and the evidence of barrier movement is not very common on the mid-Atlantic coast (Jones and Philips 2011, 168). Barrier island chains such as the Isle Dernieres and Chandeleur Islands of Louisiana have undergone considerable land loss in the past years in response to the permanent erosion of the sand by hurricanes, increased rates of SLR and limited sediment supply (Jones and Philips 2011, 168). Louisiana barrier islands are remnants of the Mississippi River Deltas formed and deserted over 7,000 years ago. These barrier islands are all diminishing in size, retreating, and the most important retreat and breaching happening during frontal passages and storms (MacCracken, Moore, and Topping 2008, 102). North Carolina Outer Banks recent studies show that Pamlico and Abermarle Sounds have undergone fully open-ocean situations at least twice in the past 2,000 years; this suggests the segmenting or removal of barrier islands in the earlier period (Jones and Philips 2011, 168). The barrier islands in Alabama and Mississippi are less than 5,000 years old (they are recent features) and are nourished by the sand washed alongshore by the wave transport from Alabama and Florida panhandle. These islands have decreased in size since the mid-1880s and the greatest erosion occurring on the east end (MacCracken, Moore, and Topping 2008, 102). Activities on Eastern United States Coast Barrier Islands Barrier islands constitute 12 percent of the global open ocean shorelines. They are susceptible coastal landforms and very famous locations for tourist development. Thus, their future in the rising sea level and the world of warming is of great concern (Fraser, Pilkey, and Pilkey 2011, 91). Historically, the eastern shores served as the Native American fishing and hunting grounds, a destination for the well-heeled travelers and a hiding place for the pirates (The Nature Conservancy 2011). The Native Americans utilized the marine resources on the barrier islands before the European settlers took them (Morton 2008, 102). The settlers used the islands for grazing their livestock. Furthermore, these settlers began building recreational facilities on the barrier islands regardless of the risks associated with tampering of the ecosystem. Colonization of the seashores for touristic and recreational pursuits in the 19th century resulted in the change of attitudes towards the coastal environments (Colten and Dilsaver 1992, 218). Throughout the 19th century, the interaction between the dynamic shorefront environments and the recreationists was one of experimenting, coping, and learning. There was little construction directly exposed on the shorelines of the Gulf Coast until the late 1800s. The wave-washed beaches were suitable for recreational activities such as bathing and sensory stimulation. However, the early coastal recreationists recognized the dangers of intermittent hurricanes well understood by the long-term dwellers. Places perceived safer were the lower wave energy shorelines like the Eastern Shore of Mobile Bay and Mississippi Sound mainland shores (Colten and Dilsaver 1992, 219). Majority of the recreational settlements were created in sheltered locations from which easy expedition of the undeveloped exposed shores was done, for example, from Port Isabel to Padre Island, Texas. Cottages and hotels were built on the higher ground (in most cases a significant distance away from the beach) and structures such dance pavilions and bathhouses were built directly besides the beach. In locations where high elevations did not exists (such as on the Grand Isle, Louisiana), structures were built a number of feet off the ground to keep the floors dry at times of periodic storm-overwash (Colten and Dilsaver 1992, 220). During the Gilded Age, there was expansion of the rail lines, the penetration of grand hotels to the southern shores, and the inception of the annual southward migration. Despite these developments, the earlier precautions regarding the shorefront settlements were ignored. Beach debris and sand dunes were tampered with in order to enhance the recreational resource. Variations of the human response to the storm-induced destruction and erosion during this era can be indicated by the case studies of Galveston, Texas and Grand Isle, Louisiana. In the 1880s, there was beachfront urbanization in both regions and before long major hurricanes hit them. Grand Isle was hit by the infamous 1893 Cheniere Caminada storm and Galveston by the 1900 infamous Hurricane (Colten and Dilsaver 1992, 220). The Importance of the Eastern United States Coast Barrier Islands The Eastern United States Coast barrier islands are the global longest stretch of barrier islands. Barrier islands as their name indicates, they guard the coastlines and they offer them important buffers to the susceptible shores and the inland regions from violent waves and storms. These barrier islands are the most important coastal features of the United States (Restore America’s Estuaries 2009). These coastal barrier islands cover approximately 85% of the oceanfront of the United States East and Gulf Coasts. In North Carolina, the barrier islands offer more than 300 miles of protective barrier to the high-energy oceanic waves linked to hurricanes and storms (Green 2008). They are directly exposed to the open sea and they make the first direct contact with storm and waves generated from hurricanes and other forms of storm. As the storm makes a landfall, they receive the highest wave actions and strongest winds. Barrier islands have the ability to withstand large storms and the odd thing is that they need natural catastrophes to persist and exist. In other words, they cannot exist in the absence of nor’easters, typhoons, and hurricanes (Restore America’s Estuaries 2009). Concisely, they have protected the eastern coastlines of the United States. Other than protecting the coastal ecosystem, they are breeding places for fish and thus offering a market for the fish in the area. Therefore, they serve the purposes of offering food and employment to the people who live there and beyond the coastal regions. Their economic significance is evident; the most economically important susceptible regions are recreational resorts built along the peninsulas and coastal barrier islands of the United Stated Gulf and Atlantic coasts (Schwartz 2005, 839). However, as indicated earlier on, these barrier islands have diminished in size and retreated due to human interference and other natural causes. Green (2008) states that majority of the East Coast barrier islands are diminishing due to rising sea level, diminishing sediment budgets (exacerbated by the human-built structures), and storms. The coastal regions of the United States are densely populated and economic development is extensive. These coastal regions are home to more than half of the America’s population. Despite been densely populated, more people are flocking to these regions (Green 2008). This can traced back to the early occupation of these areas by the Native Americans and the European settlers. References Colten. Craig, and Dilsaver, Lary, M. The American Environment: Interpretations of Past Geographies. Maryland: Rowman and Littlefield, 1992. Fraser, Mary, E., Pilkey, Keith, C., and Pilkey, Orrin, H. Global Climate Change: A Primer. Massachusetts: Duke University Press, 2011. Gray, George. Scientific Assessment of the Effects of Global Change on the United States. New York: DIANE Publishing, 2009. Green, Ann. “Barrier Islands Buffers: Network Focuses On Stabilizing Ecosystems.” Coastwatch. 2008. http://www.ncseagrant.org/home/coastwatch/coastwatch-articles?task=showArticle&id=603. Jones, Andrew, L., and Philips Mike. Disappearing Destinations: Climate Change and Future Challenges For Coastal Tourism. New York: CABI, 2011. Kusky, Timothy, M. The Coast: Hazardous Interactions within the Coastal Environment. New York: InfoBase Publishing, 2008. MacCracken, Michael, C., Moore, Frances, and Topping, John, C. Sudden And Disruptive Climate Change: Exploring The Real Risks And How We Can Avoid Them. London: Earthscan, 2008. Morton, Robert, A. “Historical Changes in the Mississippi-Alabama Barrier-Island Chain and the Roles of Extreme Storms, Sea Level, and Human Activities.” Journal of Coastal Research 24, no. 6 (2008): 1587-1600. Morton, Robert, A. National Assessment of Shoreline Change: Part 1: Historical Shoreline Changes and Associated Coastal Land Loss along the U.S. Gulf Of Mexico. New York: DIANE Publishing, 2008. Neal, William, J., Pilkey, Orrin, H., and Rice, Tracy, M. How to Read a North Carolina Beach: Bubble Holes, Barking Sands, and Rippled Runnels. New York: UNC Press Books, 2004. Nichols, Reid, C., and Williams, Robert, G. Encyclopedia of Marine Science. New York: InfoBase Publishing, 2008. Pilkey, Orrin, H., and Young, Rob. The Rising Sea. Toronto: Island Press, 2009. Restore America’s Estuaries. “Galveston Bay: Barrier Islands and Their Role in Coastal Protection.” Restore America’s Estuaries. August 2009. http://www.estuaries.org/galveston-coastal-barrier-islands.html. Schwartz, Maurice, L. Encyclopedia of Coastal Science. London: Springer, 2005. The Nature Conservancy. “Virginia Eastern Shore: The Virginia Coast Reserve.” The Nature Conservancy. Accessed November 2, 2011. http://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/virginia/placesweprotect/virginia-coast-reserve.xml. Watson, J. M. “South Carolina Barrier Spit.” USGS. November 9, 1997. http://pubs.usgs.gov/circ/c1075/barrier.html. Read More