The beach plots have been huge successes of the Walkers Quarry conservation efforts, except that there has been recent damage to DR2 which was caused by local 4×4 truck operators using the dunes as a place to play. Between 1964 and the present day, the amount of dune-stabilizing foliage has grown four-fold, and currently protects well-developed dunes in DR1 and DR3. We recommend an effort be made to exclude the 4×4 trucks from all dune areas and undertake intensive dune restoration on DR2.
- To restore beachfront sand dunes assigned plots DR1, DR2, DR3 through the use of sand-trapping fences and native species re-vegetation.
- To provide an important habitat for the nesting of leatherback turtles.
- To provide a beautiful and healthy location for the recreation of residents and visitors (without their 4×4 trucks).
- Estimated Area: 33.4 Acres
Plots DR1 and DR3 have sufficient existing vegetation cover to protect the dunes and are not in immediate need of rehabilitation. It is recommended that efforts go into DR2, while there is continued monitoring of the vegetation cover in DR1 and DR3.
DR 2 Plan – Order of Operations
1. Access Restriction
Restrict vehicles from being able to access the full length of dunes on the property, DR1, DR2, and DR3. This can be done through a combination of placing large boulders on the beach across each access point, and fencing.
2. Public Signage
In conjunction with restricted access, appropriate signs should placed at the location to inform visitors about the project. Signs should be placed at nearby major beach access points, and be large enough to be read from a distance so that people do not have to walk on the newly-accreting dune to read the sign.
Our hope is that the access restriction and the signage will discourage the 4×4 truck drivers from entering the rehabilitation zone. If this strategy does not succeed, the rehabilitation project will be futile. Are there any additional measures we can take to stop the trucks?
3. Sand Trapping Fence
One of the major mechanisms of dune establishment is sand carried by the wind from the beach towards the land. As wind speed is reduced and the sand grains fall, these sand particles will drop from the wind and accumulate, forming dunes. Sand-trapping fences are porous barriers that reduce the wind velocity sufficiently so that sand drops out of the wind stream and accumulates on both sides of the barrier. The function of sand fencing in this location is to speed up the accumulation of sand. The construction of dunes with fences is the first step in a two-phase process.
We recommend placing the fence parallel to the pre-existing dunes in DR1 and DR3, thus creating a continual natural dune that would be closest to the water, as fences are most successful when they coincide with the natural vegetation line or dune line.
Fences should have a porosity of about 50%. The porosity is the area of open space to the total projected area. Fences should be aligned parallel to the shoreline rather than be in zig-zag arrangements. The fence does not need to be perpendicular to the prevailing wind direction.
A 1.2 m (4 ft)-high fence with 50% porosity would usually fill to capacity within 1-2 years.
Almost any kind of fence can be used provided that the structure slows but does not completely block the wind. So a completely solid fence, such as plastic sheeting or open fencing (for instance, chicken wire), will not work as a viable sand fence. It is recommended that vertical wooden slats (or wooden pallets) joined with chicken wire be used. This fence should be minimum .6 m (2 ft) and maximum 1.2 m (4 ft) height.
If using pallets for construction, longer wooden stakes will be required periodically to anchor the pallets into the sand.
To determine success, monitor the rate of vertical sand accretion at the dune rehabilitation site. Marks can be made with spray paint at the top of the fence at intervals of 20 m. At each mark, the height from the top of the fence to the sand level is measured with a tape measure. These monitoring sites should be set up immediately after the fence is constructed, and then measured at one- to two-month intervals. Care should be taken not to disturb any newly accumulated sand during the monitoring activities. Monitoring will provide information on the rate of sand accretion and the time of year when it takes place.
The process of sand accretion will take a year or two, depending on the local conditions. When the sand has reached similar heights to the surrounding dunes, start the re-vegetation of the dunes (the following rainy season).
If using pallet fencing, the fencing will remain in place indefinitely, allowing the natural processes of degradation to break down the wood and nails.
4. Re-Vegetation of the Dunes
The next phase of the dune restoration is the establishment of local shoreline species.
The primary stabilizers of the dunes are perennial grasses, combined with other herbaceous plants and shrubs to mimic natural ecological communities. It is important to incorporate nitrogen-fixing species into dune ecosystems, as they’re systemically deficient in nitrogen, and this can slow the establishment of plantings. Mixed-species plantings should be placed in parallel rows 0.3 – 0.6 m (1-2 ft) apart. Arrange plantings close enough to each other to offer some mutual support against wind erosion, wind buffeting, and foot traffic. Because of the harsh conditions associated with dune restoration, transplantation is the recommended method for the re-vegetation of DR2.
Sourcing the Vegetation
The healthy vegetation in DR1 and DR3 can be drawn from those locations and be directly replanted into DR2 during this phase. 90% of transplants will come from these areas. Make sure to draw transplants from areas of thick vegetation and not to draw too many from one area. We don’t want to de-vegetate DR1 and DR3 in the process! Observation of other dune species along the same coast could be used when introducing some other species.
Once transplanting has been implemented, a surface mulch should be spread around the plants. This may consist of a layer of dead leaves or seagrass. The mulch will reduce wind and water erosion, and will promote moisture retention.
Plantings should coincide with the wet season as, during this period, there will be less moisture stress and usually lower wind speeds, thereby increasing the success rate of transplanting.
Walker’s Beach is undoubtedly one of the main nesting locations on the island and is unmatched in the size a lack of disturbance for the turtles. Walker’s Reserve has the ability to have a seriously positive impact on the long-term well-being of the Leatherback turtle population around Barbados. The dune restoration activities, suggested above, will lead us toward that goal.
*Image courtesy of CERES and the University of West Indies, http://www.cavehill.uwi.edu/cermes/docs/technical_reports/charlemagne_2006_gis_conservation_area_barbados_ct.aspx