Coastline Changes

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 1970s. 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 (http://www.tpub.com/content/aerographer/14269/css/14269_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 (http://biology.usgs.gov/s+t/SNT/noframe/cr133.htm). 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 forelands, 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 (http://calspace.ucsd.edu/virtualmuseum/climatechange1/09_2.shtml). 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