Concerns over Seven Mile Beach sand

When I was studying marine biology in college, the main point that I learned about marine sediment transport was its fluidity. When I was piloting Cayman’s deep subs in George Town Harbour, the scariest moments were the occasional, massive silt clouds that would spill over the wall. They descended upon the sub, suddenly carrying us downward in zero visibility under a hundred yards of falling sand. Tremendous volumes of sand regularly slip off the reef shelf, never to return.

It may well be that both sides of the argument recently aired concerning Seven Mile Beach have missed why deepening the spillway over the drop-off at the exit end of the SMB sand conveyor, which runs from Northwest Point to George Town Harbour, could affect the beach.

Yes, according to two respected old salts, Bob Soto and Kem Jackson, we will theoretically lose sand faster from Seven Mile Beach by deepening the spill-way, which I also believe plausible and which is consistent with R. Seymour’s report quoted in government’s rebuttal to CCMI. Seymour concludes that “At the south end, there is no transport into the system because it is the end of the line. As a result, the beach begins to disappear, beginning from the south and working northward”.

Seymour assumes that because the harbour is at the end of the line for sand transport and not the origin, that what happens there is of no consequence to Seven Mile Beach. And yet, he points out that the sand begins to disappear from south to north! This makes the harbour the main exit point over the wall for sand moving south from SMB. It’s the drain!

Let that sink in for a minute.

Physics suggests that creating a pit on the edge of the spill-way and then stirring the sand in that newly enhanced drain basin with ships’ thrusters could only accelerate the sand loss and speed its way off the beaches from whence it came – a theory worth research. Sand acts like a liquid, always seeking the lowest point while remaining subject to wave energy. It will constantly flow into the pit if we dredge the harbour from its current 20-40 feet sloping depth down to the desired working depth.

We have already done great harm to Seven Mile Beach by building too close to the sea and not on stilts, creating energy reflectors that back-wash sand off the beach and, according to Seymour, eventually down to the harbour and over the drop-off. Numerous sand chutes also spill off the wall all along the way.

At the same time that we constantly lose uncounted tons of sand, we have also alarmingly reduced and continue to reduce the major producers of sand – our big parrotfish (squab). A recent study by the University of Exeter in the Maldives found that over 80% of all new sand there actually is parrotfish poop.

We know we already have aproblem. Seven Mile Beach is visibly shrinking. I believe we need more stilts and or greater set-backs in shoreline planning and we need to let the parrotfish recover through regulation and public education. Add the fact that live hard-coral coverage has dropped from 80% to 20% and SMB looks to be in serious trouble.

There is hope if we care enough. Given enough political will, we can change our destructive behavior. Are we willing to learn and change? Build smarter? Protect our parrotfish? Ready to support and listen to marine biologists? The sooner we scientifically identify and get onto solving these known sand loss factors the better. Having said this, is it wise to risk adding yet another detriment to SMB’s precious gift by enlarging the drain at the exit end of the sand conveyor?

Good stewards do not wantonly destroy God’s gifts of renewable resources in exchange for concrete. Want a murky parking lot instead of coral reefs in clear water? Stay alert as we near the referendum vote. Those of us who have spent a lot of time looking at this have many legitimate, serious concerns and not just for the harbour itself or the sand on SMB.

This plan seems to be heavily weighted in red ink. If you are a registered voter, you owe it to yourself and to Cayman to learn about that ink and then vote your conscience for Cayman’s future!

Courtney Platt

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  1. There was a 4 year research study done for finding a sinking site for the USS Kittiwake, to be located as close to Georgetown as possible for cruise and stay over guest. This data was shared with the DOE and the CITA.
    The study was done at locations from Jackson Point (South Sound) to NW Point (West Bay). The annual sand shifts from Jackson Point to NW Point was amazing. In The late summer months NW Point had an abundance of sand at 60’ and at the West Bay Dock beach area. By early spring all this sand had shifted all along the seven mile beach coast line back to Jackson Point, where now there was an abundance of sand built up at this southern point. Inside the deep wall reef area, we had sand shifts up to 8 feet which also correlated with the annual coast line sand replenishment to the seven mile beaches.
    Being a Civil Engineer in Cayman since 1983, this deep trench dredging for the cruise ship berthing will stop this natural sand flow and displacing these natural sand shifts off the deep wall.
    The message to Government and all Cayman voters, is this deep trench dredging for cruise berthing will definitely destroy our national treasure, Seven Mile Beach forever!!!