Vanishing Sands

Southern SMB erosion “worst on record”

By Staff Writer

Grand Cayman’s Seven Mile Beach, consistently voted as one of the world’s best beaches and the main draw for its tourism industry, is currently under serious threat of further erosion if intervention does not place soon. Already, the Department of Environment is calling the erosion seen along its southern end from Plantation Village up and past Royal Palms “the worst on record”. Rising sea levels and continued building on the all-important “active beach” will lead to further serious erosion if nothing is done, they say.

The DoE has undertaken a variety of studies of the beach over the years on its long-term behaviour so have a good understanding of its natural movement. In its favour, the beach is located on the leeward side of Grand Cayman so is not exposed to frequent bad weather. However, when Cayman experiences larger waves reaching SMB’s shoreline, that can have a significant effect on the beach. In particular, two seasonal patterns affect SMB’s sand: winter fronts bringing waves from the north-west (Nor’westers) which help to deposit sand at the southern end of the beach, while summer sometimes sees waves come in from the south west, which push the sand in a northerly direction. The problem comes for the southern end of the beach when there are no Nor’westers to help push the sand south. In this scenario, the sand can fluctuate by over a 100 feet in some parts, whether that is erosion or beach growth.

However, DoE advised that the issue of sand erosion is exacerbated hugely when hard structures such as swimming pools, seawalls and properties are built in the footprint of where the sand naturally fluctuates. Where such structures are built, the beach sees accelerated rates of erosion and longer recovery times post-storms.

“Hard structures impede the natural beach processes and exacerbate erosion both at the location of the structure and it can also have knock-on effects along the wider stretch of shoreline,” the DoE explained. “This is most notable at the southern end of Seven Mile Beach where recent serious erosion events occurred on the southern end of Seven Mile Beach as a result of the near passage of two late season tropical storms in close succession.”

The DoE said that while it was likely there would be some natural recovery of the beach if the right environmental seasonal conditions presented themselves, it was clear that this current extent of erosion was one of the worst on record for the Southern end of SMB and the timeframe for a full recovery could be years, if at all.

Available solutions

There are solutions to the problem, which will only get worse with rising sea levels bringing storm waves further inland and increased storm activity and intensity, but they need serious consideration, planning and funding.

If the developments at the southern end were built away from the active beach, the beach would likely have a natural sandy beach ridge which would provide an additional source of sand to help repair the sand losses. All of the beach ridge sand reserves at the south end of SMB are locked away under the foundations of hard infrastructure or removed during the construction phase of development and used for some other purpose.

“The DoE consistently advocates for developments to be positioned away from the active beach to reduce the vulnerability of development and to preserve the coastline. However, it is for the decision-making bodies to ensure that they follow these recommendations,” they said.

In the short-term, there are measures such as beach nourishment which could recreate a beach along severely eroded sections of Seven Mile Beach, but this is only short term, and its longevity will be dependent upon the wind and wave conditions and accessibility to sand, the DoE said.

In the medium to longer term, there are options such as managed retreat which could be explored. This involves removing and rebuilding inappropriately sited infrastructure away from the sea, a complex strategy which requires a clear and deliberate plan.

“It needs extensive and fully inclusive stakeholder engagement and raises some challenging issues such as who carries the financial burden of paying for managed retreat,” the DoE stated.

The DoE warned there would be a tipping point when the beach ceases to be present under normal conditions along some parts of Seven Mile Beach because of the presence of hard infrastructure on the active beach, already seen at the northern end of Boggy Sand Road.