The limestone of Barbados’ ‘coral cap’, which covers 85% of the land surface, is highly porous, and as a result there is little permanent surface water on the island. There are no perennial rivers in the coralline region, and there have always been relatively few wetland areas. Stormwater discharge to the marine environment is ‘episodic’ rather than continuous. Such wetlands as there were originally have been significantly reduced and degraded as a result of development practices and societal attitudes, resulting in losses of associated biodiversity and ecosystem services.
Historically, the Holetown area was predominantly coastal wetland. With human development, these natural systems were replaced with ‘grey infrastructure’ like concrete channels and culverts which convey stormwater runoff to the sea, as shown in the aerial photograph comparison below.
The concrete drain on the beach between the Police Station and First Street in Holetown is an example of this. This drain is discharge outlet of a watershed or drainage basin that extends from the island’s central ridge to the coast (or ridge to reef), with a total area of 450 hectares. This watershed identified is as ‘W25’ using the nomenclature established in the 1996 Barbados Stormwater Drainage Study. ‘Seaview Gully’ is the main watercourse within this watershed. The marine area that this outlet discharges to is within the Folkestone Marine Reserve.
As is typical of coastal stormwater outlets on Barbados’ south and west coasts, the mouth of the outlet is blocked by the beach berm (sand) most of the time. Large rainfall events produce enough flow to breach the beach berm and discharge directly to the marine environment. Smaller rainfall events generate flow towards the outlet, but it is insufficient to breach the berm.
Stormwater from inland brings with it sediments and pollutants. In the interim between events, stormwater is retained behind the beach berm, and as it remains for long periods, such as in the dry season, it may become stagnant. The result is unsightly and unsanitary, with unpleasant odours and conditions that are favourable for mosquito breeding. The next event with sufficient flow to breach the beach berm brings about the ‘first flush’ effect in which this polluted stormwater is discharged directly into the marine environment.
This blockage by the beach berm, which results in the formation of a lagoon and episodic discharge to the marine environment, is a natural process. What is not natural is the human induced pollution from inland. Furthermore, the historic natural wetland area would likely have been home to mangroves and other vegetation which provide natural processing of pollutants and therefore help to alleviate this first flush effect.
In 2013, the Coastal Zone Management Unit (CZMU) executed the Holetown Waterfront Improvements Project (HWIP) – Phase 2, in which a series of shoreline protection structures and drainage improvements were installed between the Holetown Police Station in the south and Coral Reef Club Hotel in the north. The overall effect of these installations includes a substantially widened beach fronting the W25/ Seaview Gully watershed outlet.
More recently, as part of the AMCECC Programme, the Ministry of Environment and National Beautification has been working with partners to implement a small wetland rehabilitation pilot project at the W25 outlet. This pilot project is a hybrid of conventional engineering and nature-based solutions. A pre‑existing concrete channel (‘grey infrastructure’) was modified to open into a wetland and pond that is being planted with typical coastal vegetation (‘green infrastructure’).
Since the beach here is quite wide and stable (see HWIP above), there is enough space for the pond at the back, leaving beach space in front for regular use. When there is a large enough rainfall event, the sand berm will be naturally breached as usual by heavy flow, and will naturally rebuild afterwards. The difference now is that between large events, the pond will provide added storage capacity for impounded stormwater and will naturally retain the fine sediments conveyed with the runoff.
In addition, local coastal vegetation – including red mangrove – is being introduced at this site. This vegetation will naturally process pollutants, produce oxygen and store carbon. The small rehabilitated wetland will provide habitat for fishes, crabs and other types of coastal wildlife.
It will take some time after planting for the new vegetation to become established. Short and long term monitoring and maintenance is being put in place, initially to tend to the new planted vegetation in the early stages, and beyond that for general maintenance.
Stay posted for further updates on this page as planting and monitoring proceed.
If you would like to contribute to the monitoring and maintenance programme, please contact us.
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