Dear Editor,
In an SN article of May 18, it appears that the Ministry of Public Works (MPW) has decided to take some action to contain the erosion of the Georgetown foreshore which has resulted in overtopping of the sea defence at its eastern boundary. It has now authorized the construction and rehabilitation of four groynes on that stretch of seawall from Camp Road westwards to protect valuable ocean front properties in the city ward of Kingston from flooding due to the anticipated overtopping from sea water.
Unfortunately the construction and rehabilitation of four groynes will have a minimal effect on the erosion of the foreshore with the resulting overtopping in the aforementioned area. What is needed is the stable construction of a regression-resistant sea wall.
MPW’s Chief Sea & River Defence Officer (CSRO) claims that the groynes will act as wave breakers and significantly reduce erosion of the foreshore and the travelling phenomenon of overtopping, which has had the disastrous effect of flooding low-lying lands south of the sea defence.
Groynes are not considered the proper means for breaking waves or preventing large-scale erosion of the foreshore, a contributing factor for overtopping. Therefore the efforts now being expended should have been directed towards the stable construction of an appropriate seawall which can resist erosion and check the regression of the coastline, as no feasible means of arresting beach erosion has been suggested. Groynes should not be mistaken for breakwaters (wave breakers?) or jetties, structures whose primary function is to protect the areas where they are built from wave action. The primary objective of groynes is to prevent the drift or movement of materials (sand, shingle, shell) along the coast due to the action of littoral current. For them to function efficiently they should be impermeable, have a proper relationship between their length and spacing, be directed into the prevailing wave direction to avoid the effects of wave attack and erosion, and have their tops at approximately high-water level. It is not clear by observing the ongoing construction what design parameters were being used for the groynes west of Camp Road and whether they will function as desired.
Finally, the CSRO has stated that in order to keep construction costs for the groynes low, MPW will supply construction materials (stone and cement) from its stockpile, the costs for which are not reflected in the estimated cost of $20M stated to construct and rehabilitate the groynes. Because stone and cement are major ingredients needed to construct groynes it is puzzling as to why their costs are excluded from the estimated $20M stated for construction of the groynes since MPW is supplying them, and the public would want to know the real cost for the groynes. It is worth noting that the concrete mix seen delivered on site for the groynes appears to be coming from a private supplier ‒ a somewhat complex logistic arrangement.
Yours faithfully,
Charles Sohan
