Jamel Banton, Philip Warner, David Smith, Veronique Morin
The coastlines of the Caribbean are unique in many ways. Their warm waters and sandy beaches attract millions of visitors to their shores and these attributes provide an essential economic opportunity. Coastal hazards affecting the region include hurricanes, tsunami, and coastal erosion. For islands with mountainous interiors, development is often concentrated along the coastlines. This paper draws on more than 20 years of experience designing and evaluating coastal protection schemes in the region, and the related issues, constraints and opportunities are discussed. Projects in The Bahamas, St. Vincent, Guyana, Jamaica and Barbados are cited and the reasons for their appropriateness to the region and specific locations are highlighted. The paper highlights the importance of multi-criteria analyses for coastal project selection and the need for funding agencies to insist on a thorough evaluation of options at the design stage. The unique nature of both the local and regional issues must be recognized and, as such, the design parameters used must have a Caribbean focus. Stakeholder consultation is an essential component of the design process and projects should be treated as an opportunity for socio-economic enhancement as much as possible. Eco-system based approaches should also be given due consideration. Experience has shown that the regulations and codes that govern coastal development need to be updated in most cases. Further, proper enforcement of these regulations will be key if Caribbean coastlines are to survive the next century of anticipated sea level rise.
David A.Y Smith, Philip S. Warner, Jamel D. Banton
Whilst beach erosion in Negril over the past 5-10 years has gained significant media attention, the calculation of the true rates of erosion that could be used in the design of rehabilitation works requires careful analysis. Ideally, a long-term database of regular beach profile measurements would be available and could be analysed to separate beach response to storms, seasonal fluctuations and long-term trends. In the absence of this long-term data set, two main sources of beach width data have been examined. The first is aerial and satellite images from 1968, 1980, 1991, and 2003, and the second is a series of beach profile measurements taken between 2000 and 2003. In addition, a series of detailed beach profile measurements were made in 2006.
This paper looks at the available sources of beach width data and determines related erosion rates for Long Bay and Bloody Bay. The long-term vertical images were rectified and shoreline positions were estimated and overlaid for comparison purposes (1968 – 2003). In 2006, the shoreline position was obtained using differential GPS and this was also used in the long-term analysis (Figure 1 below). The 2000-2003 profile measurements were used to determine beach width variations with time for a medium-term timeframe. The width was measured from the profile origin to the shoreline and these values were extracted from the profile measurements and plotted in a time-series manner.
The analysis of images did not reveal a uniform rate of erosion over the past 40 year period, but suggested a dynamic system that is characterised by periods of erosion and recovery. However, the trend of erosion appears to be overriding from the long term perspective, as the 1968 shoreline was found to be seaward of all of the other profiles along 78% Long Bay. This finding suggests that erosion of the shoreline is continuing and is widespread.
The objective of this paper is to present a comparison of the two methods and time-scales that have been used for evaluating beach erosion rates at Negril and to provide guidance to the interpretation of these data, in reporting on and understanding the erosion-recovery-erosion cycle. In addition, through a review of hurricane activity and swell events, the impact of these events on the erosion and recovery processes are evaluated, within the context of longer-term erosion trends.
Philip S. Warner, Elisabeth A. Mondon
Over the past 5-10 years the problem of coastal erosion along the beaches of Negril has received much media exposure. There are believed to be several factors that have contributed to the problem, such as a series of damaging hurricanes and severe swell events, as well as the construction of tourism-based infrastructure close to, or at, the waters edge, poor water quality, degrading seagrass beds and declining coral reef health. The beach is typically sheltered from the Trade Winds, but when it is exposed to passing storms, the beach exhibits a noticeable response. Extensive investigative work on the Negril Beach erosion problem has been carried out for the Negril Coral Reef Preservation Society in a recent Preliminary Engineering study entitled “Beach Restoration Works at Negril”. Part of the work applied detailed coastal engineering analyses to understand the prevailing coastal processes and develop remedial engineering solutions that address the problem of beach erosion along the shoreline. The recommended Beach Restoration Works comprise the most technically viable, least-cost solution to the problem and include a first stage of beach nourishment in tandem with the implementation of nine (9) submerged breakwaters, which are intended to increase the stability of the sand.
This paper presents an evaluation of the proposed nearshore protective breakwaters using MIKE21, which is one of the most advanced coastal process models available. This model was used to simulate the short-term beach response to a swell event in order to evaluate the efficiency of the proposed breakwaters. MIKE21 works in a morphological manner and is able to simulate the real beach response by updating the seabed topography as it is modified by the computed sediment transport characteristics. For example, during a storm, beach erosion often carries sand offshore where a sandbar is formed. This sandbar affects the incoming waves, forcing them to break further offshore. This actually helps to protect the beach from further erosion and MIKE21 is able to simulate these processes.
Jamel Banton, Danielle D. Dowding
Hurricane waves and surges can have a crippling effect on economic growth in Caribbean island states. In reducing the vulnerability to these disasters, exposed areas to storm surge must first be identified and inundation levels
predicted. Various methods and models have been applied to estimate storm surge at sub-regional scales and for coastal sites and towns. The approach used to filter and utilise the hurricane data, and the statistical methods employed to develop final values are often different. The territories through different funding agencies have sponsored several projects to map storm surge, but there has not been a single unified project or approach. This paper puts into perspective the requirements for storm surge evaluation, outlines the varying approaches relevant for the region and re-emphasises the need for an established set of regional guidelines.
David A. Y. Smith, Veronique Morin
An examination has been made of multi-decadal and longer-term trends in hurricane frequency and intensity in the North Atlantic and Caribbean Basins. The investigation points to an increasing occurrence of hurricanes, which may also be more intense. There appears to be a strong link between global warming impacts and these findings. This paper presents a recommended methodology for incorporating these anticipated changes into the development of a design wave climate for coastal infrastructure in the Caribbean.Read Full Text
Scientists and Engineers around the world have naturally developed a fascination with cyclones (called Hurricanes in the North Atlantic Basin). With this fascination, we have developed a range of prediction models for cyclone-generated winds and waves. In addition, we have adapted statistical procedures to analyze the probable wind and wave conditions for different time intervals. These conditions are vital in determining the potential shoreline impacts such as storm surge levels and coastline erosion.
There are several prediction models and similarly several commonly used statistical methods. Unfortunately, these models and methods often give varying results and as such it becomes unclear as to which are most suitable for application to a particular situation. In addition, there is only a handful of measured data to inter-compare and calibrate these models.
The prediction models include complex numerical models and also simplified parametric models. The numerical models supposedly give more accurate results than the simpler and more parameterized models. However, they are far more financially and computationally expensive.
The common statistical methods of analysis are the modified extremal methods, traditionally used in river/rainfall flooding designs. To a far lesser extent, a more recently developed approach,the Monte Carlo Method, has been applied. There are several ways of applying the historical methods, which sometimes give varying results. As for the Monte Carlo Approach, there is no widely accepted published method.
The beautiful sandy beaches of the Caribbean Sea are the prime source of foreign exchange income in most of the islands. In addition, the most developed and populated areas are the coastal regions. The financial resources and the luxury of time are often not available to employ the use of complex numerical prediction models to study the probable impacts of hurricane waves on these islands. Furthermore, the Monte Carlo approach requires a large number of computations, which are usually not possible with these models. Therefore, an evaluation of the available parametric models and an assessment of the various statistical procedures is now a most relevant and necessary assignment. Even more essential, is the development of an appropriate tool to easily apply the best methods.