The examination of flood risk in the Caribbean on island of Turks and Caicos and the solutions to address flooding

Michael Thompson and Paul Donahue, Dillon Consulting Ltd., Toronto, ON, Canada


The Turks and Caicos Islands are located within the northern Caribbean, boarding the Atlantic Ocean and the Caribbean Sea.  The Turks and Caicos Islands are comprised of over 40 islands, of which 8 are inhabited.  In 2013 the Turks and Caicos Islands Government initiated a Stormwater Flood Risk Management Study to investigate the inundation that is occurring throughout the islands that is being caused by raising sea levels, low lying areas and rainfall events.   In particular, the focus of this investigation is limited to the major inhabited islands of Providenciales, Grand Turk and South Caicos.  Turks and Caicos Islands contain a number of salinas.  These salinas are low lying areas that are referred to as salt lakes or salt marshes and are considered as areas of environmental sensitivity, but are also areas that can potentially impact water levels on roads and surrounding lands. 

Dillon Consulting Limited was retained to evaluate the flood vulnerability of the three islands and recommend solutions that would address flooding on Providenciales, Grand Turk and South Caicos.  The Turks and Caicos Island Government identified chronic flooding areas, which included highways, roads, as well as commercial and residential areas.  Consideration was given to allowing safe access for emergency vehicles during the flood events.  The analysis involved the development of 2D PCSWMM hydraulic models for the study areas and analyzing for various storm events (flooding scenarios).   The purpose of the analysis was to identify areas that are vulnerable to flooding, their associated risk of flooding and the identification of solutions to mitigate the risk of flooding.  Consideration was given to the effects of raising sea levels due to climate change.  

For Providenciales, the primary area of flooding that requires immediate attention is drainage from the downtown area that makes its way past the international airport to a pump station used for discharge of flood waters to the ocean.  The combination of shallow grades, intense runoff, high tides, and undersized drainage features contribute to significant flooding around the lower lying roads adjacent to the ocean.  In addition, significant flooding occurs on the main highway crossing Providenciales (Leeward Highway) as well as the roads located on the north side of the island.  For Grand Turk the flooding occurs on the western coastal areas and overtop a number of roads adjacent to the salinas.  South Caicos had considerable flooding across a large portion of the island, in particular the low lying salinas which are hydraulically connected and influenced by sea levels and changes in tide.

The solutions developed for each of the islands considered storage, conveyance and non-structural solutions. The structural measures included, enlarged concrete channel networks, ponds, storm sewers and berms.  The non-structural measures include maintenance and trash removal, as well as public education.  High level cost estimates were developed based on preferred alternatives for each of the islands with the priority areas being identified; and may be used as preliminary conceptual cost estimates for proposed future works.

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