Natural and Human Factors Controlling Catastrophic Valley Entrenchment and Debris Fan Formation in the Bluefields River, Westmoreland Jamaica

W. Patrick Dryer, Master of Geospatial Sciences, thesis student

Dr. Robert Pavlowsky, Chairperson, Advisory Committee

Little is known about the geomorphic response of Jamaican rivers to climate, geology, and historical human disturbance. The southwestern coast of Jamaica received a record of 32 cm of rain on June 12, 1979. The rains caused extensive flooding in coastal mountain areas that damaged some local communities, including the loss of life. Reports indicated that valley areas formed temporary lakes that overflowed drainage divides and small dams to concentrate floodwaters to record stages in steep streams to produce debris flows and sediment fans.

This study investigates the effects of this extreme rainfall and flooding on the geomorphology of the present-day Bluefields River near Belmont, Westmoreland. The river drains 4.9 km2 of limestone uplands and mountain slopes and flows a distance of 1.1 km from an elevation of 75 meters to sea level. The Bluefields River was entrenched by nearly 9 meters along its middle and lower reaches and formed a large debris fan out into Bluefields Bay. Cross sections, longitudinal profiles, soil profiles, and alluvial stratigraphy were used to identify ages of landforms and variations in bed and bank morphology along the Bluefields River.

The purpose of this study is to investigate the bed channel morphology and composition of the related alluvial deposits to understand the geomorphic evolution of the Bluefields River system.

The objectives are to:

  1. quantify and describe the geomorphic effect of the 1979 floods;
  2. calculate sediment discharge to the debris fan from valley incision;
  3. evaluate the natural and anthropogenic causes of catastrophic channel change;
  4. determine the geomorphic evolution of the contemporary Bluefields River.

Bluefields Bay is now a fish sanctuary and understanding sediment inputs into the bay over different timescales is important for the future protection of the bay and the local economy.

View the Completed Master's Thesis

View a Poster Made to Present this Research (at the 40th Annual Binghamton Geomorphology Symposuim, October 2009)

Derek Total Station Bluefields River