Recommendations for the rehabilitation of Grand Anse, Grenada, following the erosion caused by Hurricane Lenny

by Dr. Gillian Cambers.[1]
December, 1999.

INTRODUCTION

A visit was made to Grenada on 01.12.99 by the Consultant, Dr. Gillian Cambers, in order to assess the beach erosion damage following Hurricane Lenny and to make recommendations for the rehabilitation of the beach. The visit was arranged by Mr. Francis McBarnette, Director of the Organization of American States (OAS) Grenada and was jointly funded by the OAS/Caribbean Planning for Adaptation to Climate Change (CPACC) project and the UNESCO/Caribbean Development Bank project on Institutional Strengthening in Beach Management in the Organisation of Eastern Caribbean States and the Turks and Caicos Islands.

The itinerary for the visit is shown in Appendix I. During the visit the entire length of Grand Anse was assessed, as well as beaches at Morne Rouge and Lance Aux Epines.

OBSERVATIONS AND ASSESSMENT

Path of Hurricane Lenny

Between 14^th and 20^th November, 1999, Hurricane Lenny moved in a west to east direction across the Caribbean Sea, from an area north of Colombia to the Lesser Antilles. Between 16^th and 17^th November, Hurricane Lenny reached Category 4 strength with sustained winds of 240 km/hour (150 mph). The storm passed south of Puerto Rico and just south of St. Croix before stalling on 18^th November near Anguilla and St. Maarten. Reports of more than 49 cm (20 inches) of rainfall were received from St. Maarten. Between 19^th and 20^th November the system headed southeast down the Atlantic side of the Lesser Antilles before heading out into the North Atlantic Ocean in a northeast direction. This hurricane was unusual for two reasons: firstly its direction was predominantly from west to east (a once in a century occurrence); secondly its strength was very unusual for so late in the hurricane season (only four other storms reached category 3 or higher strength during the month of November this century).

This hurricane generated severe swells which affected all the territories bordering the Caribbean Sea: the Greater Antilles, the Lesser Antilles, the coast of Venezuela and the Netherlands Antilles (Aruba, Bonaire and Curacao).

Effects of Hurricane Lenny on Grand Anse

Between 16^th and 19^th November, high waves 4 – 5 m (12 - 15 feet) high, approaching directly from the west, affected the west coasts of Grenada, Carriacou and Petite Martinique. These waves were superimposed on top of a storm surge, the height of which is unknown at the present time.

The effects of Hurricane Lenny were experienced along the entire west coast of Grenada. Sections of the Western Main Road were destroyed as well as several houses in Gouyave, a west coast fishing village. This present report, however, concentrates on the damage at Grand Anse.

Grand Anse is 2.6 km (1.6 miles) long and is the central focus of Grenada’s tourism industry. The entire length of Grand Anse was affected by the hurricane swells, with the most severe damage from the Grenada Renaissance Resort to the Flamboyant beach bar. The northern end of the beach to Silver Sands was also affected by the swells, but the erosion and damage was less severe here due to the protection provided by the northern headland.

Sand was stripped from the beach and carried offshore. Large volumes of sand were also carried inland and deposited in properties behind the beach. Numerous large trees fell, and two weeks after the hurricane a 1 m (3 feet) high ‘cliff’ of sand was visible at the back of the beach by the road access north of Camerhogne Park. The Cotbam Restaurant, Bar and Dive Shop was destroyed and now forms a major debris pile projecting 10 m into the sea. The low dune in front of the Spice Isle Inn was lowered more than 1 m in height.

The beach profiles (cross sections) in Figures 1 and 2 (Appendix II) show the beach one month before the hurricane and one week after the hurricane. (These profiles were measured by a team from the Grenada National Science and Technology Council, Lands and Surveys Division, Land and Water Resource Unit). The profiles illustrate the extent of the damage to the beach.

Beach Rehabilitation since Hurricane Lenny

Rehabilitation efforts have been spearheaded by the Grenada Board of Tourism, together with assistance from other government agencies e.g. the Forestry Department, as well as hoteliers and the community. These efforts have mainly consisted of clearing the debris, removing fallen trees and roots, placing sand deposited on inland properties back on the beach, redistributing sand along the beach.

RECOMMENDATIONS

1. Allow the beaches to build back naturally. During the assessment on 01.12.99, signs of beach accretion were apparent as the waves have begun moving sand from the nearshore zone back to the beach, especially in the area around the Vendor’s Market and the Spice Isle Inn. A low berm (sand bar) was forming in these areas as the waves moved the sand onshore. This process is expected to continue in the coming weeks and months. Measurements following Hurricane Luis in 1995 in the islands from Dominica to Anguilla, showed that 70-80% of the sand was returned to the beaches in the 6 – 12 months following the hurricane event (Cambers, 1996). To illustrate this effect, Appendix III shows beach profiles at Pinney’s Beach Nevis, before Hurricane Luis, one week after Hurricane Luis, and six months after Hurricane Luis. A similar process is expected at Grand Anse over the next 6 – 12 months. This will be a slow gradual process and will depend partly on winter swell activity. It is recommended that this process should be left to take place naturally and therefore no new sea defence structures should be constructed at Grand Anse in the short term.
2. Continue monitoring beach recovery. Beach measurements are carried out on a regular basis every three months by a team comprising the National Science and Technology Council, Lands and Surveys Division, Land and Water Resource Unit and the Fisheries Division. It is recommended that these measurements be conducted more frequently, at two monthly intervals, at Grand Anse for the next 6 – 12 months so as to monitor the beach recovery. In addition new reference points for measurement should be established at the Flamboyant, Coyaba (to replace the Africa Club measurement) and Silver Sands.
3. Evaluate beach recovery. Using the measurements referred to in recommendation #2, review the beach recovery in the summer of 2000. If the recovery is not as expected/predicted, then this will be an opportune time to review alternative measures such as beach nourishment (pumping sand from the offshore zone to the beach) and/or sea defence structures (seawalls, revetments, offshore breakwaters). Such measures are costly and detailed studies will be necessary prior to their design and implementation.
4. Continue ongoing beach cleaning and rehabilitation efforts. Placing sand, that had been washed inland, back on the beach should be continued. Some of this sand may then be redistributed along the beach e.g. in front of the ‘cliff’ at the road access north of the Camerhogne Park, and at the southern end of the dune in front of Spice Isle Inn.
5. Implement a coordinated revegetation plan. While the intentions behind the replanting efforts of individual property owners such as Coyaba are to be commended, it is perhaps premature to start planting now. Rather a co-ordinated replanting effort should be developed, involving several agencies and interests e.g. Forestry Department, Board of Tourism, National Science and Technology Council, hoteliers and community interests, and should take into account beach recovery rates, suitable plants to withstand sea blast, care and maintenance of the plants, wet/dry seasons. Ultimately this initiative could evolve into a Beach Management Committee which could include other beaches besides Grand Anse.
6. Remove the debris resulting from the destruction of the Cotbam Restaurant. This construction debris is at present projecting into the sea for more than 10 m. Not only does it impede access along the beach, but it is unsightly and dangerous. Wave and current action will move this debris to the north and south, making bathing and beach walking dangerous along the beach in front of adjacent hotel properties e.g. Coyaba and Spice Isle Inn. While it is understood that this property (the Cotbam Restaurant) is privately owned, the removal of this debris should be viewed as an urgent priority in view of its danger to beach users.
7. Remove the unstable standing structures at the old Silver Sands Hotel. Some of the old structures remaining from the former Silver Sands Hotel are now standing at a very perilous angle. Any wave action from winter swells or other events could result in their collapse and danger for beach users.
8. Plan for future storms. Predictions indicate that we are entering a 20 – 30 year period of increased hurricane activity in the North Atlantic basin. Besides the need to improve and continuously update disaster preparation efforts, it is necessary to implement planning measures to reduce the impact of future storms and hurricanes. One such measure involves ensuring that new coastal development is placed a ‘safe’ distance behind the active beach zone. Methods for calculating a ‘safe’ distance have been developed e.g. Cambers, 1997. The existing 50 m setback from the high water mark at Grand Anse needs re-evaluation in view of Hurricane Lenny, as do setback distances at other beaches in Grenada. Notwithstanding the above, and pending any review of the regulations, the 50 m setback regulations should be enforced at Grand Anse. This will ensure the safety of new beachfront property and the conservation of the beach in the short and long term.

REFERENCES

Cambers, G. 1996. Hurricane impact on beaches in the eastern Caribbean islands 1989-1995. COSALC Report. 96 pages.

Cambers, G. 1997. Planning for coastline change. Guidelines for construction setbacks in the eastern Caribbean islands. CSI info 4, UNESCO, Paris. viii + 14 pages.

FOOTNOTES

1. Coast and Beach Stability in the Caribbean Project (COSALC), University of Puerto Rico Sea Grant College Program, P.O.Box 9011, Mayaguez, Puerto Rico 00681. Tel: 787 832 3585, Fax: 787 265 2880, e-mail g_cambers@rumac.uprm.edu

APPENDIX I

Itinerary

30.11.99

0820 Depart Mayaguez
1730 Arrive Grenada

01.12.99

0900 Meeting with Mr. Francis McBarnette, Director OAS. Field visit and damage assessment of Grand Anse, Morne Rouge and Lance Aux Epines, with Mr. R. Morain of the Board of Tourism, Mr. Gordon Paterson of the Forestry Department and Mr. Peter Thomas of the National Science and Technology Council.1215 TV interview with Grenada National TV.
1230 Lunch Meeting with Mr. David R.L.Lin, Ambassador of the Republic of China.
1500 Technical meeting with OAS (Mr. F. McBarnette), Board of Tourism (Mr. William Joseph, Ms. Anne Isaac, Mr. R. Morain), National Science and Technology Council (Dr. James Pitt, Mr. Peter Thomas), Energy Division, Ministry of Communications and Works (Mr. John Auguste).

02.12.99

0600 Depart Grenada.
23.00 Arrive Mayaguez.

APPENDIX II

Beach profile measurements at Grand Anse before and after Hurricane Lenny

(Data provided by the National Science and Technology Council, Lands and Surveys Division and the Land and Water Resource Unit).

Beach profiles at Spice Isle Inn, Grand Anse, before and after Hurricane Lenny.

The green line (with the round markers) shows the beach profile before Hurricane Lenny, and the red line (with the square markers) shows the beach profile one week after Hurricane Lenny. Note the height of the dune and of the beach has been significantly lowered – by more than 1 m (3 feet) – as a result of the hurricane.

Beach profiles at the road access north of Camerhogne Park, Grand Anse, before and after Hurricane Lenny.

The green line (with the round markers) shows the beach profile before Hurricane Lenny, and the red line (with the square markers) shows the beach profile one week after Hurricane Lenny. Note the beach profile has been significantly lowered and narrowed and there is a very steep cut at the back of the beach.

APPENDIX III

Beach erosion and recovery at Pinney's Beach, Nevis, following Hurricane Luis, September 1995

(Data provided by the Nevis Historical and Conservation Society and the Nevis Planning Department).

Beach profiles at Pinney’s Beach Hotel before and after Hurricane Luis, 1995.

The yellow line (with triangle markers) shows the beach profile before Hurricane Luis, the green line (with round markers) shows the beach profile after Hurricane Luis, and the red line (with square markers) shows the beach profile six months after the hurricane. Note that at this site, six months later, the beach had recovered to almost its pre-hurricane size.