Coastal Storm Defenses - Assignment Example

Coastal Storm Defenses Coastal storm is nothing but the disturbance of the ordinary conditions of the atmosphere in coastal zone attended by high speed wind along with rain, snow, sleet, hail, or thunder and lightning. Blizzards, sandstorms, dust storms are also the term used for storm and the high winds are the dominant meteorological element in all these forms. Coastal flooding, cyclone, hurricanes, tornado are some of the common coastal storms. Hurricane is generally a tropical cyclone with a wind speed of 74 mph or greater. A tropical cyclone has a wind speed between 39 mph and 73 mph. Extra tropical cyclone is generally large scale storm of temperate latitudes, while the tropical cyclone which is also called as hurricane is somewhat smaller in area than the former. It is accompanied with high winds and heavy rains. On the other hand tornado or twister is a small but intense storm with very high winds. Generally it has limited duration. The thunderstorm is accompanied by brief but heavy rain showers and often by hail. Generally it is local in nature (“Storm Surge’’). Storm surge is a high flood of water caused by wind and low pressure which is most commonly associated with hurricanes. It is the most deadly aspect of a hurricane and is responsible for heavy damage during hurricanes. It is different from tidal surges which are violent surges caused exclusively by the tidal shift in sea level. Storm surge is caused by extremely high winds. This wind pushes the water rapidly and turns it into a huge wave. At the same time, the low pressure caused by the hurricane results in the rise of water level in the lowest-pressure spots and to sink in areas of higher pressure. It exaggerates the wave builds up ("Brendan McGuigan). In the beginning, a disturbance forms in the atmosphere and develops an area of low atmospheric pressure. Winds begin to move into the center from surrounding areas of higher air pressure. Warm water heats the air, and rises as it nears the center. The ocean feeds warmth and moisture into the storm, and provides energy that causes the warm air in the center to rise faster. It condenses high and creates thunderstorms. If conditions are favorable, tropical depression develops into a tropical storm, and creates hurricane. Rising air in the storms center condenses and produces heat which forcing it to rise even faster. The air is pushed out the top and more air has to rush in at the surface to take its place which kicks the ocean up more. Many a times, along the coast, storm surge is becoming the greatest threat to life and property from a hurricane. As history reveals in the past, large death tolls have resulted from the rise of the ocean associated with many of the major hurricanes that have made landfall. Usually the water in the conveyor belt contains more salt than normal which increases the waters density, and causes it to sink to greater depths. This increases the flow of deep water southward, which forces an increase in the flow of warm, tropical surface water northward. As a result the northern Atlantic becomes warmer than normal, providing the heat needed to turn hurricanes into powerful killers (“Storm Surge’’). Effects of Coastal Storms First and foremost impact is property loss. Many villages along the coastline may destroy in a short period during coastal storms. Hurricane Katrina struck the American coasts in the month of August 2005 recorded as one of the deadliest hurricane in the history of America. More than 1,836 people have been killed in hurricane and in the subsequent floods. In UK alone an estimated 1.8 million people and 1,40,000 commercial properties are at risk, and in the event of any storm nearly 4 - 5 million people could be affected (“Coastal Defenses’’). Tourism industry would have also impact heavily. When beaches are swept away, the communities rely on revenue from summer tourism would suffer financially. Priceless historic landmarks would be destroyed during coastal storm. When industrial sites are damaged, waste can potentially leach into the environment which may leads to environmental pollution. Adding, loss of productivity could harm the economy. To some extent, ocean waves erode coastlines. They shift beaches, mold sea stacks and cliffs, drag stones and sand, breach barrier islands, and driftwood. These are all geological phenomenon and takes place gradually. But, storms not only enhance the speed, but also affect the coastlines badly. The shape of a shore can change overnight during the big disturbances like hurricane, and cyclone. According to the National Ocean and Atmospheric Administration, 155 million people and over three trillion dollars of real estate in United States of America are vulnerable to coastal erosion and endangered by coastal erosion (“Coastal Defenses’’). Coastal Storm Defenses Coastal storm defense is of great importance for the opening-up and economic prosperity of coastal areas. But, natural as well as human factors are driving coastal change and make coastal regions and populations increasingly vulnerable. Over the last few years sea level has been increasing gradually, and put the population in coastal regions at risk which are the direct implications of the climate change. Climate change may lead more powerful storms in future, and may increase hurricane strength. As United States Geological Survey report says, Louisianas coastal wetlands loosing 75 square kilometers per year due to human actions like dredging and draining. As a result barrier islands of the Louisiana coast erode which opens wetlands to tides and the full force of coastal storms. The destructive threat posed by hurricanes is increasing because the buffering wetlands are constantly being destroyed. Coastal marshes, wetlands, and barrier islands which are known to be the best defenses against coastal storms are being eroded at an alarming rate due to urban development. Certain navigation channels such as Mississippi River Gulf Outlet were threatening wetlands and its communities. Oil and gas corporations were engaging in wetlands destruction, and these are responsible for 40-60% of Louisianas wetlands loss. Nation acts to avoid the worst impacts of climate change, otherwise Louisianas wetlands will be lost. According to coastal experts, we have to start the rebuilding of our coastal lines of defense at the earliest, otherwise it will cost more (“Coastal Defenses’’). For example, barrier islands, marshes and cypress swamps all are acting as natural storm defenses and protecting the Louisianas coastal communities. For every three to four miles there is a wetland which reduces the speed of storm surge nearly by one foot. Along with these natural slopes or wall which is parallel to the coast, called as levees would regulate the hurricane level storms to some extent. Strategic changes to the levee system will allow sediment and fresh water flow into the wetlands and there is an availability of technology to pump sediment from the Mississippi river directly to the marshes that need it (“Coastal Defenses’’). Wetlands and barrier islands act as good defense against storms as they are capable of protecting billions of dollars worth of oil and gas infrastructure from wave and storm damage. According to scientists, approximately three miles of healthy vegetated wetlands are capable of absorbing one foot of storm surge. If wetlands and barrier islands erode, oil and gas infrastructure will become exposed to open water and increasingly susceptible storm damage. Collapse of wetlands and estuarine marshes may result in the intrusion of saltwater which will escalate salinity levels and disturb the delicate balance between fresh and salt water. Storm tides, waves, and currents severely damage marinas and boats. In estuaries salt water intrusion endangers the public health. It may kills vegetation, and can send animals, such as snakes and alligators, fleeing from flooded areas. Coastal barriers are unique land forms which serve as the mainlands first line of defense against the impacts of severe coastal storms. They are usually located at the interface of land and sea, and provide protection for diverse aquatic habitats. There are types of barriers such as bay barriers, tombolos, barrier spits, barrier islands which are described by their relationships to the mainland. Along with these, dune and beach barriers, mangroves are also functions as coastal barriers (“Coastal Defenses’’). They are the foundations of a strong economy and healthy environment. They offer habitats that support a variety of fish and wildlife, and protect the mainland communities from coastal storms. One of the longest and best defined chains of coastal barriers in the world occurs along the United States shoreline bordering the Atlantic Ocean and the Gulf of Mexico which contains over 400 barriers and totals about 2,700 miles of shoreline. Fringing mangroves are bands of mangrove along subtropical or tropical mainland shores in areas of low wave energy, and many of these areas are located behind coral reefs, which together provide significant protection for the mainland from storm impact(“Homeland Security Newswire’’). Generally mangroves have deep, extensive, intertwining roots systems perfectly adapted to saline conditions, and bind the earth firmly against catastrophic storm surges. A second line of coastal defense is provided by beach grasses, like papyrus or bulrushes, or sedge and wire grass. Unfortunately, many of these natural coastal defenses have been torn up, either to provide lumber or to make way for agriculture, fisheries or tourism. Coastal forests are being increasingly decimated by human activities ranging from oil production to shrimp or rice farming and tourism. For example, once a beach in Myanmar ran hundreds of feet deep with mangrove swamps, but now the same beach is either a shrimp farm or a tourist resort. Substantial financial investments have been made in the construction, maintenance, and monitory of these defense systems. Constructed wetlands, concrete barriers, marshes, built up earthen levee systems provide additional protection, and in many cases become the first line of defense. Construction of seawalls and breakwaters are generally expensive, and the costs to build protection in the face of sea-level rise would be enormous (“Homeland Security Newswire’’). Governments are investing huge amount to build costal storm defenses. Even though they burden heavily on the government’s exchequer, that is necessary to save the property and human lives in future. In a revamp process Orleans’ 560 km perimeter has been fortified by toughened levees. Cement walls were constructed which more than 9 meters high, and gates that will grind have shut when flood water nears. Walls have been built with steel reinforced ones shaped like an inverted "T," making it harder for a storm surge to topple them. The mud levees that Katrina washed away are now bolstered with stronger clays, while pump stations were replaced with flood-proof safe houses. US government has invested nearly $14.45 billion to upgrade this defense. Experts feel that with the construction, the city is certainly safer than it was on 29 August 2005, when Katrina made landfall. On that day, nearly 8.5 meter surge went on to overpower levees and flood walls which were poorly connected and constructed (“Homeland Security Newswire’’). There are many artificial defense systems are available, and are constructed along the shoreline to get protection against coastal storms. Wooden groynes which looks like wooden fences are designed to stop material being moved along the beach by long shore drift, and are built down the beach built at right angles to the coastline. The side facing the wave suffers erosion, but the side protected from the waves allows deposition to occur and sand builds up there. They have a life span of approximately 20 to 30 years. Gabion groynes are large steel or stainless steel mesh cages that are filled with rocks, and they run down the beach, at right angles to the coastline. They have a life span of approximately 20 - 25 years. If the steel used are stainless, they last much longer. Rock armor or rip rap are large boulders of 10 tons or more are piled up along the shoreline to form a type of sea wall. Rocks are connected while leaving gaps between them to allow water through. These are seems to be very effective. Generally granite and basalt are used which are strong and resistant to erosion (“Coastal Defenses’’). Beach nourishment is one more defense against coastal storm. In this method new beach would be created or widen the existing beach by dumping or pumping sand from elsewhere onto an eroding shoreline. It replaces beach or cliff material that has been removed by erosion or long shore drift. Usually sand is filled once in a year, and is relatively inexpensive option, but it requires constant maintenance. Breakwaters are structures constructed on coasts as part of coastal defense to protect a harbor from wave energy or deflect currents. They are constructed either some distance away from the coast or built with one end linked to the coast. Cheaper materials like rubber tires and oil drums are usually used for its construction. They may be either fixed or floating depending on normal water depth and tidal range. When waves hit these breakwaters, their erosive power is concentrated on these structures some distance away from the coast, and there is an area of slack water behind the breakwaters (“Coastal Defenses’’). CONCLUSION Coastal zones are dynamic area of natural change and of increasing human use as they contain rich resources to produce goods and services. They are home to most commercial and industrial activities. With three quarters of the world population expected to reside in the coastal area by 2025, human activities originating from here will impose an inordinate amount of pressure on the global system. As the effects are deadly, better and long-term plans are needed to manage coastal storms in order to protect natural resources and mitigate the effects of increased storms on human infrastructure. Works Cited Bruce G. Sharky, FASLA. “Creating Disaster Resiliency in Tropical Storm Regions: Re-Building for Flood Resilient and Sustainable Coastal Louisiana Communities and the Mexican Gulf Coast’’. World Scientific and Engineering academy and society. Web. 7 December. 2010. Homeland Security Newswire. “Katrina: five years on, Are New Orleans’ storm defenses strong enough?’’. Web. 30 August. 2010. Jeffress Williams S, Benjamin T. Gutierrez, Robert Thieler E, & Elizabeth Pendleton. “Geological Effects and Coastal Vulnerability to Sea-Level Rise, Erosion, and Storms’’. American Society of Civil Engineers. Web. 7 December. 2010. National Hurricane Center. “Storm Surge Overview’’. Miami, Florida. Web. 06 December. 2010 The geography site. “Physical Management: Coastal Defenses’’. Web. 30 November. 2010. Read More