Unusually high tides continue to cut across Cayman’s coasts, knocking over Casuarina trees along Frank Sound and eroding local beaches. The Meteorological Office said the high tides or “king tides,” affected by last month’s supermoon, are due to gradually subside.
Over the past 30 days, the astronomical phenomenon has led to tides rising up to 12 inches above sea level, according to data collected by a monitoring sensor at George Town harbor.
The so-called “king tides” occur twice a year, when the sun, moon and earth are aligned. If the alignment coincides when the moon is closest to Earth, the boost in gravity from the moon’s proximity makes the extreme tides known as king tides, according to National Geographic.
“As the moon orbits the Earth, it is closest to the Earth on Aug. 10, which is called the supermoon. Since then, the orbit of the moon has gradually been moving further away,” said John Tibbetts of Cayman’s National Weather Service. “A full moon does exert extra force over the tides, and a supermoon accentuates that force with fuller high tides and lower low tides.”
Residents in low lying and costal areas, including Snug Harbour, North Sound and Red Bay, reported flooding due to the high tide.
In the north side of Grand Cayman, people living near the water said they had not seen tides that high in 60 years, the Cayman Compass reported on Sept. 8.
Tim Austin of the Department of Environment said, “It is the highest tide I’ve seen for a long while.”
The king tide is also causing some erosion along local beaches, and the flooding uprooted several trees.
“Beach erosion causes trees or sea walls to fall in the water … I walk South Sound beach as part of our turtle monitoring program; there’s a lot of erosion there too,” said Mr. Austin.
Turtle nests impacted
Department of Environment officials say the rising water levels paired with heavier wave action have the potential to affect nesting turtles in the lower lying areas of Cayman and Cayman Brac, but so far the impact has been limited.
Loggerhead and green sea turtle species can be found nesting in Cayman, as breeding season runs from May until November.
“Turtle nests will not hatch if they are flooded or eroded away but can withstand some wash-over by waves,” said DoE research officer Janice Blumenthal. “Even after the immense storm surge during Hurricane Ivan, some turtle nests hatched in Grand Cayman.”
The high tides prompted Department of Environment staff and volunteers to sweep local beaches for any signs of turtle nests at risk of being washed out to sea.
“DoE staff and authorized volunteers in Grand Cayman and Cayman Brac relocated several nests to higher ground. Despite these efforts, we estimate that about five nests were lost to flooding and erosion,” said Ms. Blumenthal.
She said the loggerhead turtle nests are particularly vulnerable to high tides, since they nest closer to the water. Fortunately, though, “most of the loggerhead nests have already hatched,” she said. Loggerheads nest earlier in the year. Green turtles begin nesting in July and lay their eggs higher up the beach near the vegetation line, so the majority of nests were unaffected by the recent high tides, said Ms. Blumenthal.
“For the remainder of the turtle nesting season, routine nest examinations will allow us to evaluate the impact of the high tides in stopping development of eggs or eroding nests,” said Ms. Blumenthal.
The king tide followed shortly after two earthquakes were felt earlier this month, sparking concern among some residents as to whether the events were linked.
These concerns prompted Lands and Survey officials to investigate the landmass and sea level further but found no link.
The recent seismic activity had no effect on the positions of the Lands and Survey’s Continuously Operating Reference Stations which help monitor tectonic plate movement in the event of earthquakes, according to Lands and Survey officials.
“Whilst the water level at high tide has been increasing, there is no discernible upward or downward movement in the land mass of either Grand Cayman or the Sister Islands,” said Rupert Vasquez, director of Lands and Survey.
Lands and Survey officials are also monitoring five tide gauges, which have been installed throughout the islands, to carry out a reassessment of Cayman’s mean sea level.
This will help officials to determine any changes that may have occurred to the tide over the years. “The tide gauges have been useful in measuring the extent of the recent high tides and comparing them with data from previous years,” said Mr. Vasquez.
According to the Meteorological Office, the next supermoon is expected to occur on Sept. 28, 2015.