Beach Erosion Web In Active Hurricane Cycles example essay topic

Table of Contents Introduction 2 Countering The Effects of High Seas 2 Hurricanes 3 Beach Protection 5 New Protection Methods 6 Conclusion 6 References 7 Introduction Coastline changes due to weather and human intervention represent a major concern for coastal planners all over the world. Coastline changes, not only has an effect on citizens who own property by the seaside, it also has a major effect on our business here at McDuff. While beaches may be vacation spots for some, their disappearance through erosion a great loss of business for our company. The purpose of this report is to inform our coastal planners and stakeholders of ways to prevent coastal erosion in the Caribbean. Shorelines are areas of continuous change.

Natural forces of wind and water interact with the land and cause shifts between water and land. These shifts between water and land have been taking place for centuries but it has become a major issue in the Caribbean islands since tourism became the major industry in the 1970's. Despite being a major value here at McDuff, beaches have not been perceived as areas needing management, protection and funding. Environmental awareness has been growing slowly due to the numerous hurricanes that have past through the region.

These dramatic events bring home to everyone the importance and vulnerability of the region's beaches. This report will give information regarding: countering the effects of high seas, hurricanes, structures for beach protection, and new protection methods. This report provides information on these situations and offers ways to protect the beaches in the future. Countering The Effects of High Seas Waves, tides and ocean currents are among the several natural forces that cause beach changes. One cause of considerable beach erosion is swell waves. Swell waves are seas that have moved out and away from the area in which they were formed.

Because of their different wave lengths and wave speeds, waves move outward from the windy areas where they formed, and separate into groups of waves with distinct wave periods. In the Caribbean, swell waves are usually caused by intense mid-latitude storms in the North Atlantic Ocean, which travel thousands of kilometers south affecting the west, north and east coasts of the islands in the winter months from October to April (web 60. htm). Figure 1: Effects of Accretion (Komar, 1976) During the summer months, when the seas are calmer and the waves smaller, beaches tend to build up. This process is known as accretion (web).

If the amount of winter erosion exceeds summer accretion, there is overall erosion with the land behind the beach being eroded as the beach retreats inland. The rate of retreat is called the erosion rate. Erosion may be due to one or more factors: for example, a severe winter swell, a recent hurricane, the death of an adjacent coral reef or interference in the supply of sand. Conversely, if accretion exceeds erosion, the beach gets wider over time and accretionary features, such as cuspate foreland's, tom bolos, spits and bars, may develop (see Figure 1). Hurricanes Extreme events such as hurricanes are the major cause of shoreline changes in the Caribbean.

Many hurricanes originate as tropical waves off the west coast of Africa and travel across the Atlantic Ocean gaining strength from the warm ocean waters (web 2.'s html). As tropical waves strengthen, they pass through several stages, including tropical depression and tropical storm before reaching hurricane strength. Once a system reaches tropical storm strength, it is named. Hurricanes are further classified into five categories based on wind speed (see Figure 2). The wind speeds in categories one to five refer to sustained wind speeds. Actual gusts may be much higher.

Most hurricanes are experienced in September in the Caribbean (Bacon 1978). Scale # Category Sustained Winds MPH Damage Examples 1 74-95 Minimal Florence (1988) LA, Charley (1988) NC, 2 96-110 Moderate Kate 1985, Bob 1991, 3 111-130 Extensive Alicia 1983 TX, 1938 New England, 4 131-155 Extreme Andrew 1992 FL, Hugo 1989 NC 5 155 Catastrophic Camille 1969 MS, Labor Day Hurricane 1935 Fl Keys Figure 2: Hurricane Categories (web hurricanes. htm) Scientists that have studied hurricane weather patterns say that hurricane generation in the North Atlantic Ocean occurs in 20-25 year alternating cycles of activity and relative in activity. The evidence indicates that we have now entered an active hurricane cycle, which is expected to continue for the next two decades. The years 1995 and 1996 were especially active, 1995 registering as the second-most active year on record with nineteen named storms (web). Figure 3: Beach Erosion (web in active hurricane cycles there can be years with below average hurricane activity. Tropical storms and hurricanes generate waves that move out of the immediate vicinity of the hurricane to affect other islands as swell waves.

Considerable damage may occur to beach systems as a result of high seas, raised water level, high winds and heavy rain fall. Hurricane waves erode the beaches and penetrate farther into the land behind the beach causing flooding, erosion of sand dunes and destruction of coastal highways and buildings. Beach Protection There are three main groups of solid structures which protect land and beaches: structures built parallel to the shore, structures built at right angles to the shore, and offshore structures like offshore breakwaters. Structures built parallel to the shore are generally made of steel, concrete, rock or wood, and are designed to protect land and buildings from erosion by the sea. They are the most common means of protection found on island beaches. They come in all shapes and sizes.

The most common structures built parallel to the shore are retaining walls and bulkheads. Retaining walls are often built to protect buildings and private property (See Figure 4). Though the walls do help to save buildings it does not prevent the erosion of beaches. Bulkheads are designed to protect land from wave damage.

Bulkheads are also ineffective in preventing beach erosion (See Figure 5). Figure 4: Retaining Wall Figure 5: Bulkheads Groynes are structures that are built at a right angle to the shore. Beaches strung between natural headlands are very stable and they do not experience long-shore erosion as much. Groynes are artificial headlands, running out into the sea.

Wet sand gets trapped in between two preventing the sand from escaping the area. Groynes can be ugly in appearance and do little to help the beaches replenish themselves. Breakwaters are basically with a sea wall. They are very effective at retaining sand to form wet beaches; however, they are mostly used for lakes because in the ocean, breakwaters are easily destroyed by storms. New Protection Methods There are several new techniques being used to protect beaches from erosion, including beach drainage and artificial seaweed. Beach Drainage is recent development that places a drainage pipe under the sand below the high tide level (See Figure 6).

The drainage pipe conducts water to a collection point from where it is pumped out. The water is then led back to the sea. This method recognizes that many beaches are sick because their sand cannot dry. These beaches usually lie too flat. By draining the high tide region, the water table is lowered and the sand has a better chance to dry.

Sea wind then completes the re nourishment of the beaches. The method is quite simple to implement and energy can be saved by pumping only during the low tide and by day when the sand can dry. Another recent invention that was designed to help protect the beaches is artificial seaweed. Unfortunately this does not share the same success as beach drainage. The seaweed was design to collect sand from the water forming an offshore sand bar. This sand bar was then supposed to stop wave action around the beaches.

However, the seaweed did not hold up in the strong Caribbean currents and was ineffective. Figure 6: Beach Drainage (Coastal Stabilization Inc. 1989) Conclusion In conclusion I think year by year we are steadily learning more about beach erosion. With more advanced studies I think we can take a major step in protecting our beaches in the Caribbean.

Bibliography

Bacon, P.R. 1978.
Flora and Fauna of the Caribbean, an Introduction to the Ecology of the West Indies. Key Caribbean Publications Ltd, Port of Spain, Trinidad. Komar, P.D. 1976.
Beach Processes and Sedimentation. Prentice-Hall Inc., Englewood Cliffs, New Jersey. Coastal Stabilization Inc. 1989.