Environment and development in coastal regions and in small islands

Hurricane impact on beaches in the eastern Caribbean Islands 1989 - 1995

7.  EFFECTS OF THE 1995 HURRICANES ON THE ISLANDS FROM ANGUILLA TO  DOMINICA

The characteristics of Tropical Storm Iris and Hurricanes Luis and Marilyn have been described in Section 4.  This section will quantitatively describe the effects of these storms on the beaches of Anguilla, Antigua-Barbuda, St. Kitts, Nevis, Montserrat and Dominica.  Beach monitoring programmes were established in these islands before the storms so the impacts of the storms can be quantitatively determined.   In most of these islands the beaches were re-measured in mid to late September, 1995, after the three storms, thus it is not possible to determine the effects of the individual storms.

7.1  Anguilla

Tropical Storm Iris passed just to the east of Anguilla.  However, any erosion or coastal changes caused by this storm were completely overshadowed by Hurricane Luis, the centre of which passed 28 km (18 miles) east of Anguilla between 4th and 6th September, 1995.  All the coasts of Anguilla were impacted by the hurricane force waves.

Anguilla is a low island in the northern Leeward Islands.  It consists of a coral platform built on top of a submerged volcanic base.  The coastline consists of coral sand beaches, low rock outcrops and limestone cliffs.  The island is surrounded by coral reefs and there is an extensive barrier reef off the north coast.  There are extensive sand dunes behind some of the beaches and several salt ponds. There are several small islets and sandy cays near the main island.

Beach monitoring was established at seven beaches in Anguilla in 1992.  In 1994 six new beaches were added including two offshore cays.  A total of 38 sites are measured on thirteen beaches, see Appendix IV for the location of the monitored beaches.  Analysis of the monitoring data showed that at the seven beaches started in 1992, the beaches were accreting prior to Hurricane Luis.  These beaches were : Shoal Bay West, Cove Bay, Sandy Hill Bay, Sile Bay, Captains Bay, Shoal Bay and Meads Bay.  Profile width was increasing at an average rate of 1.2 m/yr, (Cambers, 1996). 

Photograph 1. Rendezvous Bay, Anguilla, October 1995. The beach is covered with a thick mat of dead seagrass.

Hurricane Luis caused immense damage to all the beaches of Anguilla.  In addition damage to mangroves, seagrass beds and coral reefs was widespread and severe.  Many of the beaches were covered with thick carpets, more than 1 m thick, of dead seagrass, see Photograph 1.  Offshore surveys carried out after Hurricane Luis indicated that 20% of rich seagrass beds present before the hurricane, were reduced to traces in 1996, (Bythell and Buchan, 1996).  Similarly dead Acropora palmata reefs were degraded and in some cases reduced to bare rock and nine new coral rubble berms were recorded.  A secondary impact of the loss of the Acropora palmata reefs may be to reduce the capacity of these reefs to act as natural breakwaters at certain beaches, this could influence the amount of erosion in the future.

Beach measurements were taken in June, 1995 and at the end of September 1995.  The area of the profile was compared before and after the hurricane, this was calculated as a percentage change.  Then the change in profile width was calculated as an absolute value in metres.  Finally the change in position of the edge of the land or the base of the sand dune was determined from the profile plots.  The data for each site at each beach are shown in Appendix IV, the data are summarized below in Table 7.

Two small sandy cays : Sandy Island and Scilly Cay were completely covered with water.  After the hurricane, Sandy Island did not exist, except below water.  On the main island of Anguilla, two north coast beaches received the most severe damage : Barnes Bay and Meads Bay.  Both of these beaches are open to the north and have no significant coral reef protection.  At Barnes Bay the sand was stripped from the beach, see Photographs 2 and 3.  At Meads Bay the dunes were eroded and the Frangipani Hotel was severely damaged.  Figure 8 shows the beach profile before and after Hurricane Luis at the Meads Bay Central site.  The beach was lowered by more than 2 m and the dune, which had been 30 m wide, was eroded back behind the reference point.  On the south coast, Rendezvous Bay, Cove Bay and Shoal Bay West showed the most severe erosion and there was property damage at Rendezvous Bay (Cambers, 1996).  At Maundays Bay, which was not measured prior to Hurricane Luis, villas were left perched near the edge of 3 m high sand “cliffs”.

Photograph 2. Barnes Bay, Anguilla, September, 1994. Note the wide sand beach.	Photograph 3. Barnes Bay, Anguilla, October, 1995. The beach has been stripped of sand by Hurricane Luis leaving a bare rock platform.

On average the beaches narrowed by 8.7 m (29 ft).  The land edge retreated inland a similar amount, 8.9 m (29 ft).  This latter parameter is regarded as a permanent loss, since although the beaches recover after a hurricane, the actual position of the beach will be further inland, see also Section 3.1.

In order to try and assess the extent of beach recovery, the pre hurricane data for June 1995, have been compared with the data for January 1996.  (More recent data were not available at the time of writing).  The profile area for January 1996 has been calculated as a percentage of the value for June 1995.  Similarly the profile width for January 1996 has been calculated as a percentage of the value for June 1995.  Thus these values show the amount of recovery as a percentage of the pre-hurricane values.  The profile width has also been calculated in absolute terms.  The data are summarized below in Table 8 and the individual data for each beach are contained in Appendix IV.  These data refer to the main island of Anguilla only and recovery data were only available for 15 of the 29 sites since so many reference points had had to be re-established after the hurricane.

Four months after the hurricane, the profile area and width values showed the beaches had recovered to 75% of their pre-hurricane levels.  However, profile width was still an average 8.7 m less that before the hurricane, this may partly be related to the fact that the January 1996 data collection followed a major winter swell event.  Reference to Appendix IV shows that there was tremendous variation between sites with the least recovery taking place at Meads Bay and Shoal Bay West.

7.2  Antigua-Barbuda

Tropical Storm Iris passed over the south side of Antigua.  The centre of Hurricane Luis passed directly over Barbuda and 40 km (25 miles) north of Antigua between 4-6th September, 1995.  All the coasts of Antigua and Barbuda were impacted by the hurricane force waves.

Antigua is a low island in the Leeward Islands, the topography varies from the hilly volcanic region in the southwest to the flatter limestone area in the northeast.  The coastline is very indented with numerous bays and offshore islands.  Barbuda is a low limestone island, 40 km north of Antigua, elevations reach 30 m (100 ft) in the east, but most of the island is only a few feet above sea level.  A lagoon runs along the western side of the island separated from the sea by a long narrow sand bar.   The coastline is fairly straight and is backed by extensive sand dunes.  Both islands are surrounded by coral reefs.

Beach monitoring was established at thirteen beaches in Antigua in 1991, by 1995 six additional beaches had been added to the monitoring programme.  A total of nineteen beaches (43 profiles) are monitored in Antigua.  In July 1995, monitoring was started at six beaches (8 profiles) in Barbuda.  Appendix V shows the monitored beaches.

Prior to Hurricane Luis ten beaches were showing erosion in Antigua and six beaches were accreting (Black et al., 1996).  Of considerable concern was the erosion on the northwest coast from Dickenson Bay to Fort James.  No beach change trends are available for Barbuda prior to Hurricane Luis.

Hurricane Luis, combined with Tropical Storm Iris, caused immense damage to the beaches of Antigua-Barbuda and to coastal infrastructure.  There was also widespread damage to mangroves, seagrass beds and  coral reefs, however, no quantitative assessment has been conducted of this damage.  Following the hurricane there was extensive mining of sand in Antigua as the coastal areas were cleaned up.  Thus considerable volumes of sand were removed from the beach system by the hurricane and by man.  Beach sand mining remains a serious problem in Antigua.

Many coastal hotels were damaged by flooding and the hurricane waves, especially at Dickenson Bay and Runaway Bay on the northwestern coast; Galley Bay and Hawksbill Bay in the Five Islands Peninsula; and Blue Waters Bay on the north coast.  In Barbuda, the sand bar enclosing the Codrington Lagoon was breached in at least two places allowing moderately sized vessels to enter the Lagoon.  This sand bar was 75 m wide in July 1995.  At least one of these cuts was still open one year later.

Beach measurements were taken in July 1995 in Antigua and Barbuda and again at the end of September, 1995.  Profile area before and after the hurricane were compared and the difference computed as a percentage change.  The change in profile width was calculated as an absolute value in metres.  Finally the change in position of the edge of the land or the base of the sand dune was determined from the profile plots.  The data for each site at each beach are shown in Appendix V, the data are summarized below in Table 9.

All the beaches in Antigua showed erosion with the exception of Lignumvitae Bay (Jolly Beach).  The most severely eroded beaches were on the west coast, Darkwood Beach and Crab Hill Bay in particular.  The beaches on the northwest coast from Dickenson Bay to Fort James also experienced severe erosion, see Appendix V.  When the beaches were grouped by coast, it was found that the west coast received the most damage followed by the south coast and finally the east coast (Black et al., 1996).  (No beaches are measured on the north coast). 

There was considerable variation in the amount of erosion between adjacent beaches in Antigua.  This could be related to the indented nature of the coastline and the exposure of a particular beach.  Very sheltered bays such as Pigeon Point, Falmouth and Yorks Beach showed lower erosion rates than the more exposed open bays such as Crab Hill Bay and Runaway Beach, see also Appendix V. 

In Antigua on average the profile area decreased by 23% and the profile width narrowed by 4.9 m (16 ft).  The land/dune edge retreated inland a similar amount (4.9 m or 16 ft).  This is regarded as a permanent loss, since although the beaches recover after a hurricane, the position of the beach will be further inland, see also Section 3.1.

Figure 9. Beach Profiles at Cocoa Point,  Barbuda, Before and After  Hurricane Luis

In Barbuda only three of the six beaches could be measured after the hurricane due to difficulty of access.  Here the erosion was most severe on the south coast at Cocoa Point and Dulcina Hotel.  In Barbuda the erosion was more severe than Antigua, this is to be expected since Barbuda was closer to the centre of the storm.  In Barbuda, on average the beach area decreased by 40% and the dunes retreated by 17.7 m (58 ft).  The beaches showed only slight narrowing.  Nearly all the beaches are backed by extensive sand dunes, these were eroded during the storm and some of their sand reserve was transferred to the beach.  Figure 9 shows the beach/dune profile at Cocoa Point before and after the storm.  After the hurricane, the dune had been eroded back 20 m, but some of the sand had been transferred to the beach which had a significant berm (crest).  As a result beach width had changed very little.  

In order to try and assess the extent of beach recovery, the pre-hurricane data for July 1995, have been compared with the data for May 1996.  (More recent data were not available at the time of writing).  The profile area for May 1996 has been calculated as a percentage of the value for July 1995.  Similarly the profile width for May 1996 has been calculated as a percentage of the value for July 1995.  Thus these values show the amount of recovery as a percentage of the pre-hurricane values.  The profile width has also been calculated in absolute terms.  The data are summarized below in Table 10 and the individual data for each beach are contained in Appendix V.  Data for beach recovery in Barbuda were not available at the time of writing.

Figure 10. Beach profiles at Runaway Beach  Hotel, Antigua, Before and One Year  After Hurricane Luis

Eight months after the hurricane, the average profile area and profile width values showed that in Antigua the beaches had virtually recovered to their pre-hurricane values.  Reference to Appendix V showed, however, that there was considerable variation between beaches.  In some ways the average data are misleading for they mask the changes in profile shape and the position of the dune/land edge.  For instance at Runaway Beach (Site B - Runaway Beach Hotel) the beach width data showed that the beach was wider than its pre-hurricane condition, thus one might conclude that recovery was complete.  However, when the profiles are plotted graphically, see Figure 10, it can be seen that the base of the dune (or land edge) was 8 m (26 ft) further inland eight months after the hurricane.  In addition the dune was much lower in height.  Thus while the beaches may have recovered to a large extent, the “permanent” effect of the hurricane has been to push the dune/land edge further inland.

At other sites morphological changes may be impeding recovery.  For instance at Morris Bay serious erosion was recorded after the hurricane and there had been little recovery up to May 1996.  The erosion has exposed a beachrock ledge in the inter-tidal zone.  This may be acting as a wall and reflecting the wave energy thereby causing more turbulence and impeding the beach recovery at this site.   

Photograph 4.   Darkwood Beach, Antigua, July 1996.  The beachrock ledge out in the sea indicates a  previous position of the beach.

At other sites, beachrock ledges out in the sea indicate the previous position of the beach, see Photograph 4 which shows the beachrock at Darkwood Beach on the west coast.  This beach used to be separated from the road by a low sand dune with many shade trees.  This beach has been heavily mined for many years and the beachrock ledge provides visual evidence of the previous position of the beach.

At Lignumvitae Bay (Jolly Beach) several breakwaters and groynes were constructed after the hurricane.  These have resulted in some considerable localized accretion and the data for this beach have been omitted from the average recovery figures computed above.  

7.3  Nevis 

Tropical Storm Iris passed to the east of Nevis and caused little damage.  The centre of Hurricane Luis passed 90 km (56 miles) to the east of Nevis between the 4th and 6th September, 1995.  The infrastructural damage was less severe than during Hurricane Hugo in 1989 presumably because the centre of that storm passed closer to Nevis, see Section 6.2.  Nevertheless telephone and electricity services were interrupted due to the wind damage to the poles, parts of the island main road were flooded, there was also structural damage to the Charlestown Waterfront where the finger pier and sections of the boulder protection had been damaged.  Several coastal properties were also damaged, particularly along Pinneys Beach.  While there was only minor damage at Pinneys Beach Hotel, there was extensive damage to the Four Seasons Resort, particularly to the pier, the beach restaurant and swimming pool.  Several beach bars in the vicinity of Golden Rock had been destroyed.  The Beachcombers Restaurant had been damaged and Sandpiper Restaurant to the north had sustained major structural damage, (Physical Planning Unit, 1995).  Coastal structures along the north coast had received less damage. 

As discussed in Section 6.2, beach monitoring at seventeen sites was established in Nevis in 1988, the programme has been continued without interruption to the present.  Thus the database for Nevis reflects the impacts of two major category 4 hurricanes, one in 1989 and the second in 1995.

Hurricane Luis caused immense damage to the west coast beaches of Nevis and lesser damage to the north coast beaches.  Based on observations, damage to mangroves, seagrass beds and coral reefs was widespread (Physical Planning Unit, 1995).  Many of the west coast beaches were covered with thick mats of dead seagrass which must have originated from the seagrass beds several hundred metres from the shore.  Sand and debris was deposited in the mouths of many of the west coast wetlands resulting in water stagnation.  The vegetation within 40 m of the shoreline suffered salt infiltration and all the vegetation suffered from wind damage.  No data are available of the impacts on the coral reefs.

Beach measurements were taken in June 1995 and in the middle of September, 1995.  Profile area before and after the hurricane were compared and the difference computed as a percentage change.  The change in profile width was calculated as an absolute value in metres.  Finally the change in position of the edge of the land or the base of the sand dune was determined from the profile plots.  The data for each site at each beach are shown in Appendix VI, the data are summarized below in Table 11.

The erosion was most severe at Pinneys Beach, Gallows Bay, Cades Bay, Hurricane Hill and Nisbett Plantation.  The geographical distribution of the beach erosion is very similar to that recorded during Hurricane Hugo in 1989, see Section 6.2.

When the average figures are compared, the beach erosion caused by Hurricane Hugo and Luis was similar.  Both hurricanes caused major erosion on the west coast.  At the sites from Gallows Bay South to Hurricane Hill the average beach erosion rate was -11.1 m in 1989 and -7.1 m in 1995. 

At the other sites the pattern was more variable.  The beaches at Newcastle showed accretion after both hurricanes, while at Nisbett and Indian Castle there was erosion, but at lower rates than the west coast.  In addition the profile data may not always give a complete picture of beach changes.  For instance the beach at Mosquito Bay accreted by at least 4 m after the 1995 hurricanes (personal communication Leonard Huggins), although the profile site, which is at the southern end of the bay, did not display this change.  The beach at Mosquito Bay appears to have accreted over recent years.  The headland to the north provides a considerable degree of protection, and it may also receive sand from the north coast.

In order to try and assess the extent of beach recovery, the pre hurricane data for June 1995, have been compared with the data for March 1996.  (More recent data were not available at the time of writing).  The profile area for March 1996 has been calculated as a percentage of the value for June 1995.  Similarly the profile width for March 1996 has been calculated as a percentage of the value for June 1995.  Thus these values show the amount of recovery as a percentage of the pre-hurricane values.  The profile width has also been calculated in absolute terms.  The data are summarized below in Table 12 and the individual data for each beach are contained in Appendix VI.  

Seven months after the hurricane the beaches had recovered to 90% of their pre-hurricane levels on average.  This recovery is higher than that recorded after Hurricane Hugo.  One factor that needs to be taken into consideration is that in November 1995, the beach in front of the Four Seasons Hotel at Pinneys Beach was replenished with dredged sand.  Between 10,000 and 15,000 cubic metres of sand were dredged from 9 m (30 feet) water depth, 3-400 m offshore and pumped onto the beach (Physical Planning Unit, 1995b).  Some of this sand was moved along the beach by wave action and may have influenced the recovery of the sites along Pinneys Beach.

Figure 11. Beach Profiles at Pinneys Beach  Cotton Ground in 1989 and 1996

Along the west coast of Nevis it is possible to observe the progressive retreat of the dune/land edge inland.  Figure 11 shows the beach profile at Pinneys Beach - Cotton Ground, when it was first measured in March 1989 and the most recent measurement in March 1996.  The edge of the dune has retreated inland 15 m (49 ft).  This measurement reflects the impacts of two major hurricanes passing close to Nevis in 1989 and 1995.

Similarly the proximity of buildings in the coastal zone provides visual evidence of the retreat of the coast.  Photograph 5 shows a newly constructed beach bar at Pinneys Beach Golden Rock in 1983.  Photograph 6 shows the demise of the same beach bar (repainted green) after Hurricane Luis in October 1995.

Photograph 5.   Beach Bar at Pinneys Beach,  Golden Rock, Nevis, 1983	Photograph 6.   Beach Bar at Pinneys Beach,  Golden Rock, Nevis, 1983

The beach bar is now in the sea following the hurricanes of 1989 and 1995.  (The building was demolished in 1996).

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