Written by Christopher Alexis
Junior Research Officer
This article was published in the Daily Express on Thursday 26th August, 2010 under the title: Columbus Bay faces serious coastal erosion.
Columbus Bay is a 4 km stretch of beach located between Los Gallos and Corral Point on the Cedros peninsula in south-west Trinidad. In the 19th century, this area was an important centre for produce, especially coconuts. It was also the southern terminus of the gulf streamers – marine transportation vessels which operated between villages. The coconut industry has since declined but is still important and there are no gulf streamers today. The main activity in the area is now fishing.
Columbus Bay is fringed by the Los Gallos and Icacos mangrove swamps and the Constance Coconut Estate. It is exposed to near-shore currents from the Columbus Channel that flows into the Gulf of Paria sometimes in excess of 2 knots to the west. The geology of the area comprises unconsolidated sandstones and recent alluvium deposits, while the bay is composed of grayish-brown, medium–grained, quartz rich sand. The bay is influenced by coastal processes which operate within it, such as winds, waves, currents and tides. The geology and the orientation of the bay have therefore made it susceptible to erosive forces.
Erosion on the southwest peninsula at Columbus Bay and Corral Point has been occurring for centuries. In the early 1900s there was a prominent headland at the Los Gallos Point which intercepted some of the incoming waves to Columbus Bay and so dissipated the wave energy. This headland has all but disappeared and what is left is now identified as the ‘sisters’ - three stacks which have withstood the erosive power of the waves thus far. As this headland continues to erode, the wave energy reaching the bay is expected to increase and possibly accelerate the erosion.
The Institute of Marine Affairs (IMA) has been monitoring the southern section of Columbus Bay for the past twenty years. The general finding is that the bay experienced erosion at the rate of approximately 2 m per year from 2004 to 2008, and that erosion has increased towards the western section of the bay. Simultaneously, there is accretion (increase in land by sediment from the water) occurring at Punta del Arenal, just south of Corral Point. However, the sediment being deposited at Punta del Arenal is not from Columbus Bay but from the cliffs on the south coast of Trinidad.
There have been several attempts at arresting the erosion in this bay by installing various coastal protection structures, beginning in the 1980s. Revetments consisting of tyres, and groynes consisting of tree trunks were installed in separate instances; mangrove seedlings were also planted. They did not work. In September 2008, three groynes (perpendicular structures which extend from land into the sea which trap sediment) were installed at the northern section of the bay by the land owner, and, more recently, two shorter groynes were added.
Columbus Bay is being monitored by the IMA to determine if the groynes are effective or not. Further research on the coastal processes, including bathymetry and oceanography, is needed in Columbus Bay to ascertain the cause of the erosion and the sediment transport pathways which exist within the bay.