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Environment and development in coastal regions and in small islands |
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Environment and development in coastal regions and in small islands |
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ANALYSIS OF BEACH
CHANGES IN ANTIGUA AND BARBUDA 1996 – 2001
Volume 1
Assessment Report June
2003
RESULTS
Beach Changes at Individual Beaches
This section gives a general description of the quantitative and qualitative changes at each of the monitored beaches in Antigua and Barbuda.
Antigua Sites
Dickenson Bay: There are four sites at this beach. Between 1996 and 2001, the beach at Dickenson Bay was showing erosion. The mean profile area decreased by 1.10 m2 and the profile width receded at a rate of -0.59 m/yr. This beach continues to be one of the main beaches for tourism development in Antigua and Barbuda.
Runaway Bay: There are three (3) measurement sites at this beach. Between 1996 and 2001, this beach was showing accretion, the mean profile area increased by 4.10 m2 while the mean profile width increased at a rate of 0.46 m/yr. Following Hurricane Luis in 1995, beach recovery continues along segments of the beach. However, there was some slight erosion on the northern end of the beach following serious erosion the previous period.
Beach Scene: Fort JamesFort James Beach: There are two (2) measurement sites at this beach. Between 1996 and 2001, this beach was showing erosion, the mean profile area decreased by 11.76 m2 while the width decreased at the rate of -0.21m/yr.
Deep Bay: This beach is relatively protected but the two (2) measurement sites were showing erosion. Between 1996 and 2001, the whole beach is showing decreases in mean profile area (-6.01 m2) and width (-0.73 m/yr).
Yorks Beach: There are two (2) measurement sites at this beach. Between 1996 and 2001, this beach was showing accretion, both the mean profile area and width increased drastically (17.6 m2 and 0.90 m/yr, respectively). This represents major recovery following periods of sand mining combined with the effects of Hurricane Luis. There were small amounts of erosion on the northern end of the beach during the reporting period.
Stony Horn Beach: There are two (2) measurement sites at this beach. This beach was showing accretion. Between 1996 and 2001, the mean profile area and width increased by 4.12 m2 and a rate of 0.52 m/yr, respectively. This beach has not yet recovered to its pre-1995 levels.
Mosquito Cove: One site is measured at Mosquito Cove. Over the years, dredging of the channel into Jolly Harbour and sand mining have affected the coastal processes. Erosion is the dominant process along this beach. Between 1996 and 2001, the mean profile area and width decreased by 4.12 m2 and at a rate of -1.39 m/yr, respectively.
Crab Hill Bay: One site is measured on the beach at Crab Hill Bay. Between 1996 and 2001, extensive construction of buildings occurred on this beach. Accretion is the dominant process, the mean profile area and width increased by 14.67 m2 and at a rate of 0.34 m/yr, respectively. Deposits of sand are necessary for compensation for lost sand on the beach during times of grounds swells, when erosion is the dominant coastal process.
Morris Bay: Morris Bay has one (1) measured beach-monitoring site. Accretion is the dominant process along this beach for the period 1996 – 2001. The mean profile area and width increased by 2.98 m2 and at a rate of 0.37 m/yr, respectively. Even with this rate of accretion, this beach has not yet recovered to its pre-1995 levels.
Lignumvitae Bay: Three (3) sites are measured at Lignumvitae Bay. Between 1996 and 2001, accretion is the dominant process along this beach. The mean profile area and width increased by 5.24 m2 and at a rate of 0.23 m/yr, respectively. This may be due to the effects of the groynes built along that beach.
Ffryes Bay: Ffryes Bay has three (3) sites that are measured. For the period 1996-2001, the whole beach experienced reductions in mean profile area (-9.77 m2) and width (-0.53 m/yr) indicating that erosion is the dominant process.
Darkwood Beach: There are three sites measured at Darkwood Beach. Between 1996 and 2001, the beach experienced erosion at both ends but the mean profile area (2.26 m2) and width (0.42 m/yr) indicate that accretion is the dominant process. This varies between the different ends of the beach.
Marmora Bay: For the period 1996-2001, erosion has been the dominant process along Mamora Bay. The mean profile area and width were -0.62 m2 and -0.09 m/yr, respectively.
Falmouth Beach: Accretion is the dominant process on Falmouth Beach between 1996 and 2001. The mean profile area was 0.96 m2 while the profile width was decreasing at a rate of -0.08 m/yr. This beach is narrowing slowly.
Pigeon Point Beach: Two (2) sites are measured at Pigeon Point Beach. Between 1996 and 2001, erosion was the dominant process with the beach experiencing erosion at both ends with mean profile area and width of -1.10 m2 and -0.07 m/yr, respectively.
Half Moon Bay: There are three (3) sites that are measured at Half Moon Bay. Between 1996 and 2001, accretion was the dominant process along this beach. The mean profile area and width increased by 5.67 m2 and at a rate of 0.31 m/yr, respectively. Segments of this beach, continue to experience periodic erosion.
Long Bay: Long Bay has two (2) beach monitoring sites. Between 1996 and 2001, erosion was the dominant process at this beach. The mean profile area and width decreased by 0.48 m2 and at a rate of - 0.25 m/yr, respectively.
Dutchman Bay: Three (3) sites are measured at Dutchman Bay. For the period 1996 – 2001, erosion was the dominant process along this beach. The mean profile area decreased by 0.57 m2 and the width was reducing at a rate of -0.30 m/yr.
Jabberwock Beach: There are two (2) sites that are measured at Jabberwock Beach. Erosion is the dominant process along this beach. During 1996-2001, the mean profile area was -1.15 m2 while the profile width decreased at a rate of 0.11m/yr.
Cocoa Point Beach: Three (3) sites are measured at Cocoa Point Beach. Between 1996 and 2000, accretion was the dominant process along this beach. Even though the southern point was eroding, the mean profile area and width were 0.23 m2 and 0.73 m/yr, respectively.
Gravenor Bay (Spanish Point): Between 1996 and 2000, accretion was the dominant process along Gravenor Bay. For that period, the mean profile area and width were 0.67 m2 and 1.01 m/yr, respectively.
Dulcina Hotel: Accretion was the dominant process along Dulcina Hotel, between 1996 and 2000. For that period, the mean profile area and width were 0.18 m2 and 1.32 m/yr, respectively.
Palmetto Hotel: Accretion was the dominant process along Palmetto Hotel. For the period 1996-2000, the mean profile area and width were 1.6 m2 and 5.97m/yr, respectively. Shifting dunes characterize this beach.
Low Bay (Palm Beach): Between 1996 and 2000, erosion was the dominant process at Low Bay with mean profile area and width of -0.10 m2 and -0.80 m/yr, respectively.
Two-Foot Bay: For the period 1996-2000, accretion was the main process at Two-Foot Bay. The mean profile area and width during the period were 0.26 m2 and 2.40 m/yr, respectively.
Overall Beach Changes 1996-2001
The average beach changes between 1996 and 2001 are shown in Tables 5 and 6. The data is also shown graphically in Figures 6, 7 and 8. For the period 1996-2001, eleven (11) of the monitored beaches on Antigua were showing erosion at an average rate of –0.40 m/yr. These beaches were:
Dickenson Bay
Fort James Beach
Deep Bay
Mosquito Cove
Ffryes Bay
Falmouth Beach-0.59 m/yr
-0.21 m/yr
-0.73 m/yr
-1.39 m/yr
-0.53 m/yr
-0.08 m/yrPigeon Point Beach
Mamora Bay
Long Bay
Dutchman Bay
Jabberwock Beach-0.07 m/yr
-0.09 m/yr
-0.25 m/yr
-0.30 m/yr
-0.11 m/yrEight (8) of the monitored beaches on Antigua were showing accretion at an average rate of 0.49 m/yr. These beaches were:
Runaway Bay
Stony Horn Beach
Yorks Beach
Lignumvitae Bay0.46 m/yr
0.52 m/yr
0.90 m/yr
0.23 m/yrDarkwood Beach
Crab Hill Bay
Morris Bay
Halfmoon Bay0.42 m/yr
0.34 m/yr
0.37 m/yr
0.31 m/yrFor the period 1996-2000, on Barbuda, one (1) monitored beach was showing erosion, Palm Beach (-0.80 m/yr). For the same period, the other five (5) monitored beaches were showing accretion at an average rate of 2.40 m/yr. These were:
Gravenor Bay
Two Foot Bay
Palmetto Hotel1.01 m/yr
2.40 m/yr
5.97 m/yDulcina Hotel
Cocoa Point Hotel1.32 m/yr
1.30 m/yr
Table 5. Barbuda: Individual Beach Changes
Beach Change in Profile Area
1996-2000 m2Change in Profile Width
1996-2000 m/yrGravenor Bay 0.67 1.01 Two Foot Bay 0.26 2.40 Low Bay/Palm Beach -0.10 -0.80 Palmettol 1.60 5.97 Dulcina 0.18 1.32 Coco Point Site A 0.44 1.04 Site B 0.33 3.05 Site D -0.07 -0.19 Mean 0.23 1.30
Table 6. Antigua: Individual Beach Changes
Beach Change in Profile Area
1996-2001 m2Change in Profile Width
1996-2001 m/yrDickenson Bay Site A -0.82 -0.05 Site B -0.27 -0.59 Site C 0.04 -0.71 Site D -4.32 -1.30 Site E -0.15 -0.32 Mean -1.10 -0.59 Runaway Bay Site A 1.18 -0.06 Site B 7.10 0.51 Site C 4.03 0.92 Mean 4.10 0.46 Fort James Beach Site A -24.32 -0.72 Site B 0.80 0.31 Mean -11.76 -0.21 Deep Bay Site A -7.04 -1.27 Site B -4.98 -0.19 Mean -6.01 -0.73 Stony Horn Beach Site A 3.53 0.49 Site B 4.70 0.54 Mean 4.12 0.52 Yorks Beach Site A 1.83 -0.20 Site B 32.28 2.00 Mean 17.06 0.90 Mosquito Cove -12.52 -1.39 Lignumvitae Bay Site A 3.04 -0.07 Site B 16.27 1.64 Site D -3.59 -0.87 Mean 5.24 0.23 Ffryes Bay Site A 6.27 1.09 Site C -19.29 -1.76 Site D -16.30 -0.93 Mean -9.77 -0.53 Darkwood Beach Site A -3.22 0.51 Site B 16.16 1.23 Site C -6.15 -0.48 Mean 2.26 0.42 Crab Hill Bay 14.67 0.34 Morris Bay 2.98 0.37 Falmouth Beach 0.96 -0.08 Pigeon Point Beach Site A -1.92 -0.28 Site B -0.27 0.15 Mean -1.10 -0.07 Mamora Bay -0.62 -0.09 Half Moon Bay Site A 12.21 0.53 Site B 3.41 0.50 Site C 1.39 -0.09 Mean 5.67 0.31 Long Bay Site A 0.48 0.10 Site B -1.44 -0.60 Mean -0.48 -0.25 Dutchman Bay Site A 11.80 1.06 Site B -14.06 -2.37 Site C 0.56 0.40 Mean -0.57 -0.30 Jabberwock Beach Site A 0.17 0.44 Site B -2.46 -0.65 Mean -1.15 -0.11
Figure 6. Antigua: Changes in Profile Area, 1996-2001
Figure 7. Antigua: Changes in Profile Width, 1996-2001
Beach Under Attack: Valley Church
Figure 8. Barbuda: Changes in Profile Area, 1996-2000
From the beach monitoring data collected, certain general conclusions may be formulated. Based on the methods of validation for the data, during and after input, it is assumed that errors in the data are minimal. The calculated means therefore give the average conditions existing on a particular beach.
Under normal conditions, longshore currents produce longshore drift along the foreshore. This produces seasonal variations on the different segments of the beach. One side of the beach may experience erosion while there is accretion on the opposite end i.e. seasonal erosion and deposition. This effect depends on the location of the beach, leeward or windward coast, its topography and the characteristics of the prevailing winds (the Northeast Trade Winds ). It is difficult to determine the effects of tides and tidal currents on the processes operating on the beach.
Most of the monitored beaches in Barbuda expanded in profile width during the period 1996-2000. The average rate of increase for the entire island was 0.27 m/yr. However, all the Palmetto Hotel Sand Mining Dickenson Bay monitored beaches that were accreting fell within a range of 1.01 to 5.97 m/yr, i.e., well above the average for the monitored beaches on the island. Specific sections of these beaches have periodically experienced erosion, especially during periods when Barbuda came under the influence of some tropical weather system. The beach along Palmetto Point experienced considerable variations in profile width throughout the year. This may account for the high accretion rates. The Palmetto Hotel is always in danger as it was built close to the coastline. Even though Two Foot Bay is exposed to the Trade Winds (on the windward side), it still experienced a high rate of accretion. Offshore coral reefs provide temporary shelter.
Palmetto Hotel
Sand Mining
Dickenson BayIt is significant that Low Bay (Palm Beach) is the only monitored beach in Barbuda that experienced an overall decrease during the reporting period. This beach borders the narrow strip of land, enclosing the Codrington Lagoon. The fact that Palm Beach is eroding may have implications for the proposed development of the area.
Boon Bay
Marina Bay
Emerald CoveOn a whole, the monitored beaches in Antigua experienced a slight rate of decrease of -0.04 m/yr. However, the monitored beaches that were eroding fell within a range of –0.07 to –1.39 m/yr, i.e., all more severe than the average for all monitored beaches on the island. It is difficult to determine the exact cause (s) of the general trends. The following may have some impact, whether individually or combined:
Construction of structures close to the shoreline (buildings, seawalls, groynes, revetments, etc,)
Sand mining on or near to a beach
Deposition of material, including beach nourishment (sediments/deposits include boulders, sand, marl, etc,)
Removal of beach materials, and vegetation from close to the beach
Dredging and the digging of trenches on the beach
Marina development.
Natural forces, including hurricanes, tropical storms and depressions, storm surge, groundswells, sea level rise.
There are wide variations in the characteristics of beaches where erosion dominate. These cannot be distinguished based on the degree of shelter of beaches, beach location, orientation and use.
Rocky Coastline
Sandy BeachAlthough The Fisheries Division (FD) is the main partner agency responsible for beach data collection and analysis (The Fisheries Division are also developing the capacity for wetlands, sea grass and coral reef monitoring), the updated beach change database and software ‘Beach Profile Analysis’ were installed at the FD, DCA within the CDB-UNESCO project. For the DCA, the benefits of monitoring go beyond data collection, and include observation and assessment of new structural developments, changing beach uses, restriction of beach access, nature of beach dynamics, etc. The officers of DCA, particularly those who are directly involved in the monitoring of development activities, should become knowledgeable about all aspects of their island’s beaches and can thus play an active role in beach management and the enforcement of regulations.
As in other islands, one of the major problems encountered in beach-monitoring is the loss of profile reference points during hurricanes, even when they are located a considerable distance inland from the vegetation line. When this happens, new reference points have to be located, which obviously interrupts the data trend for that particular site. One solution to this problem involves fixing the position of the beach profile reference points with a global positioning system (GPS). Lost reference points can be located spatially after a hurricane with a fair degree of accuracy, however, changes in the height of the point will not be reflected.
The proliferation of hard structures, particularly vertical sea walls, on the beaches in Antigua is another serious problem. However, this will need a concerted effort involving several agencies. Even in Barbuda, which has a low level of beachfront development, there are examples of serious erosion and loss of buildings (August/September 2000). The implementation of the building setback guidelines, developed in 1998, would assist in reducing the problems caused by developments positioned too close to the active beach zone. Beach sand mining continues to be a problem in Antigua. Existing environmental laws related to sand mining needs to be strengthened and implemented.
One of the problems present in Antigua and Barbuda is the sectoral nature of government and the difficulties this poses for fields such as integrated coastal management. There has been much talk about the sharing of information (findings, conclusions, applications) but the difficulties involved in actually sharing data are yet to be fully resolved. Issues such as data ownership and the value of data need further discussion.
The beach-monitoring programme can be further improved with the geo-referencing of the reference points for individual beach sites. This would make the reference points more permanent. The computer software would also need to be modified to accommodate GPS readings. This could be achieved through the incorporation of the data into a geographical information system (GIS).
The following recommendations can help in the preservation and sustainable use of beach and other coastal space:
Expansion of the beach-monitoring programme to include more beaches including non-sandy beaches. In the long run, more characteristics of beaches may be measured. This can improve the aspect of ‘representativeness’ of beaches in Antigua and Barbuda.
Development and implementation of a comprehensive integrated Coastal Development Framework for Antigua and Barbuda; this should incorporate development both on land as well as in the nearshore coastal waters. This requires the coordination of several government agencies.
Implementation of the established Coastal Development Setback Guidelines for Antigua and Barbuda
Development of a policy for the management of sand as a national, natural resource, including the development of suitable alternatives to the use of beach sand as a construction material
In the long term, to educate schoolchildren, their parents and communities in the scientific monitoring and wise management of their beach resources; they should also be involved in the monitoring activities.
Continuation of beach-monitoring activities and ensuring that the reports are shared with all stakeholders. A policy of sharing costs of these activities may be necessary.
Development of linkages and the sharing of experiences with agencies responsible for beach-monitoring within the Caribbean and other similar regions of the world.
REFERENCES
Black et al., 1996 a. Analysis of Beach Changes in Antigua and Barbuda between 1992 and 1995, Volume 1 Assessment Report, COSALC report, 36 pages.
Black et al., 1996 b. Analysis of Beach Changes in Antigua and Barbuda between 1992 and 1995, Volume 2 Data Report, COSALC report, 93 pages.
Cambers, G. 1995. Year of the hurricanes. Sea Grant in the Caribbean, Puerto Rico, October–December 1995, pp. 1–3.
Cambers, G. 1996 a. Hurricane Impacts on Beaches in the Eastern Caribbean Islands, UNESCO – UPR SGCP, 96 pages.
Cambers, G. 1996 b. CSI 1: Managing Beach Resources in the Smaller Caribbean Islands: Workshop papers, UNESCO – UPR SGCP, 270 pages.
Cambers, G. 1997. Planning for Coastline Change: Guidelines for Construction of Setbacks the Eastern Caribbean Islands, CSI info 4 UNESCO, Paris, 14 pages
Cambers, G. 1998. Planning for Coastline Change 1: Coastal Development Setback Guidelines in Antigua and Barbuda. COSALC Report, UNESCO – UPR SGCP, 63 pages
Cambers, G. 2002. Wise Practices for Coping with Beach Erosion: Antigua and Barbuda, UNESCO Publications, 9 pages.
James, P. 2001 a. Coastal erosion hazard mapping for Antigua and Barbuda: Technical summary. OAS/USAID Post-Georges Disaster Mitigation Project, 31 pp.
James, P. 2001 b. Coastal erosion hazard mapping for Antigua and Barbuda. Non-technical summary. OAS/USAID Post-Georges Disaster Mitigation Project, 11 pp.
Perch, L. (2001) Beach Management: An Integrated Adaptive Approach. CPACC Publications, 25 pages.
http://www.nhc.noaa.gov/pastall.shtml
Appendix 1. Major Tropical Systems Impacting Antigua and Barbuda 1995 - 2001
YEAR TROPICAL SYSTEM Name Type Effective Date Location 1995 Chantal TD Jul. 13 North Iris TS Aug. 27 East Marilyn H Sep. 14 West Sebastian TD Oct. 23 North Luis H Nov. 5 Landfall 1996 Bertha H Jul. 7 North Edouard H Aug. 31 X North Fran TS Sep. 8 South Isadore H Sep. 28 X North 1997 Erika H Sep. 6 North Grace TS Oct. 15 X North 1998 Bonnie TS Aug. 20 North Dannielle H Aug. 27 X North Georges H Sep. 20 Landfall 1999 Emily TS Aug. 26 X East Floyd H Sep. 11 X North Jose H Oct. 20 Landfall Lenny H Nov. 19 Landfall 2000 Chris TD Aug. 19 East Debby H Aug. 21 South Helene TD Sep. 16 South 2001 Chantal TD Aug. 16 X South Erin TS Sep. 5 X East Iris TD Oct. 4 X South Jerry TS Oct. 8 X South
H – hurricane TS – Tropical Storm TD – Tropical Depression X – Extra
