Date of Graduation

Spring 2019

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology, and Planning

Committee Chair

Robert Pavlowsky

Abstract

The geomorphic effects of flooding are poorly understood in the karst, mountain watersheds along the southwest coast of Jamaica. This study describes the flow path and geomorphic response of an extreme flood event in the Brighton-Blue Hole watershed (BBHW) (6.8 km2) near Belmont, Westmoreland, Jamaica. A tropical depression classified as a >100-year rainfall event produced 32 inches of rain in a 24 hour period in Westmoreland on June 12, 1979. For this study, geomorphic indicators of flood disturbance in BBHW were assessed in 2017-18, finding that channel system responded to the flood with channel incision, debris flows, and flooding in communities. Flood effects were controlled by: (i) a structurally controlled fault block valley which decreased the elevation of the watershed divide allowing piracy of floodwater from BBHW, across the divide, and into the Bluefields River increasing flood stage there; (ii) karst depressions at progressively descending elevations which caused floodwaters to become impounded and thus attenuated stream power downstream; (iii) a morass/wetland and mangrove forest system separated from the sea by a beach barrier thus created a low area which slowed and retained flood waters before they flowed to sea via a culvert under a coastal highway; and (iv) overtopping and failure of the rim of a karst depression which produced the most destructive flood and channel response, including 9 deaths. A flood risk map was created for communities in BBHW using the areas of inundation by floodwaters and locations of geomorphic effects for reference. BBHW is relatively resilient to flooding when compared to neighboring watersheds. However, climate change and future development in the watershed threaten to increase the potential for flood damage and create higher risk to the community.

Keywords

fluvial geomorphology, resilience, extreme flooding, karst, Jamaica

Subject Categories

Earth Sciences | Geology | Geomorphology

Copyright

© Sarah M. LeTarte

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