Date of Graduation

Summer 2010

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology, and Planning

Committee Chair

Robert Pavlowsky

Abstract

Little is known about the geomorphic response of Jamaican rivers to climate, geology, and human disturbance. The southwestern coast of Jamaica received a record of 32 cm of rain on June 12, 1979. Reports indicated that valley areas formed temporary lakes, overtopped small dams, and produced debris flows. This study investigates the effects of this extreme flooding on the geomorphology of the present-day Bluefields River near Belmont, Westmoreland Jamaica. The river drains 4.9 km2 of limestone uplands and mountain slopes. This study evaluates evidence from longitudinal profiles, multiple cross-sections, Colonial maps, historical aerial photographs, oral histories, and sedimentological analysis to identify previous channel bed elevations and evaluate current channel morphology. The Bluefields River was entrenched by nearly 9 meters along its middle and lower reaches. In addition, Goat Gulley, its major tributary, was also incised along its lower and upper segments. Debris flows formed a large debris fan extending over 150 m out into Bluefields Bay. About 70% of the 1979 fan volume still remains today. While Colonial maps indicate that a delta fan always existed at the river mouth, the shoreline configuration was similar from the late 1700s to before the flood with little expression of the debris fan as now present. Therefore, the return period for this type of hydro-geomorphic event is >300 years. While causes are mostly related to climate and geology factors, human modification of the landscape may have contributed to increased rates and extent of channel incision, thus increasing sediment delivery. Bluefields Bay is now a fish sanctuary and further studies of sediment inputs to the bay over different timescales may be important for maintaining a healthy fishery.

Keywords

Jamaica, rivers, channel morphology, debris flows, floods

Subject Categories

Geology | Geomorphology | Hydrology

Copyright

© William Patrick Dryer

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