Flooding at Johnson Ghut during the 2003 November Floods. Photo: GIS

Floods are probably the most recurring, widespread, disastrous and frequent natural hazards of the world. Johnson’s Ghut and several other areas throughout the territory have been susceptible to flooding over the years.

Flood hazard mapping is a vital component for appropriate land use planning in flood-prone areas. It creates easily-read, rapidly-accessible charts and maps which facilitate policy makers, engineers, planners, insurers and disaster managers to identify areas of risk and prioritise their mitigation or response efforts. It is also a prerequisite for flood insurance schemes.

The DDM announced on Friday that it has completed the first ever flood hazard map for Johnsons Ghut watershed and now plans to replicate this project within other major watershed areas, as well as lobby for use of the data in planning and development . The project produced flood hazard maps which delineate inundation zones and water levels within the Johnson Ghut catchment.

“The results of the project confirmed the susceptibility of Road Town to intense rainfall events and provides probabilistic inundation depths in the town,” said DDM’s Senior Technical Planning Manager Ms. Cynthia Rolli. “These maps may be used to identify flood hazard zones, to guide zoning policy and the design of infrastructural works along the upper ghut and through Road Town.”

She said the Johnson Ghut watershed was chosen because it is located in a highly populated and important area of the island and has traditionally presented serious flooding problems. The Johnson Ghut catchment drains an area of approximately 60 hectares.

Ms. Rolli further explained, “The main channel passes through Road Town and is hydraulically connected to the ocean at the harbour. Elevations of some areas around the city are close to mean sea level and so, during high tides, water from the sea creates a backwater effect at the mouth of the Johnson Ghut. A rainfall event occurring during high tides would lead to a significant increase in water depths within the channel and surrounding flood plain.”

All data from the project has been integrated into the Territory’s Geographic Information System for use by various departments which have access to this system.

The DDM said it will continue to work closely with the Public Works, Survey and the Town and Country Planning Departments to ensure that the outcome of this project is properly utilized and implemented.

Building professionals and environmental consultants are being urged to use the data from the flood mapping project for any development proposed within the Johnson’s Ghut watershed, so that appropriate mitigation measures can be incorporated into the design and construction of development proposals and plans to prevent damage to life and property from flooding.

Flood management and control are necessary to ensure the optimal exploitation of the land and proper management and control of water resources that flow along very steep hillsides and into a very narrow coastline and out to sea. Flood management also considers the protection of the marine environments and coastal waters. These cannot become technically feasible without effective flood hazard maps.

The DDM received project support from Michael Adamson of Adamson Land Surveyors Ltd., Shawn Boyce of the Caribbean Institute for Meteorology and Hydrology and Dr. Vincent Cooper, a hydrological engineer from the University of the West Indies, St, Augustine Campus, Trinidad and Tobago.

The DDM has been chosen as a pilot under the Caribbean Satellite Disaster Project, which will allow for the use of satellite and digital remote sensing images to be applied to the other areas to be modeled and to provide a greater level of accuracy in the flood models.