Geomorphic Assessment of a Coastal Montane River in Southwest Jamaica

Authors: Mark Bowen*, Minnesota State University, Mankato, Matthew H. Connolly, Department of Geography, University of Central Arkansas, Toby Dogwiler, Department of Geography, Geology, and Planning, Missouri State University, Robert T. Pavlowsky, Department of Geography, Geology, and Planning, Missouri State University, Brianna Beseler, University of Wisconsin Oshkosh
Topics: Geomorphology, Earth Science, Water Resources and Hydrology
Keywords: fluvial geomorphology, tropical, climate change, deforestation, Jamaica
Session Type: Poster
Day: 4/5/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded

Geomorphologic understanding about river channel form and response is lacking for coastal montane rivers in tropical regions. To address this lack of knowledge, this study reports on variations in channel morphology and substrate of the Robins River, which drains coastal mountains of southwest Jamaica in Westmoreland Parish. Jamaican watersheds are especially susceptible to hurricane impacts due to a history of colonial deforestation beginning in the 1600s and more recent agriculture and urban disturbances. Robins River drains uplifted white limestone, originates from an elevation of ~700 masl, and flows ~7.5 km to sea level. Field surveys were completed in June 2018 at six main channel sites distributed from headwaters to near the mouth and two major tributary sites. Information was collected on channel cross-section, longitudinal profile, bed substrate, bank condition, and geomorphic disturbance indicators. Channel cross-section areas along the main channel are relatively uniform in the downstream direction. Interestingly, pool-riffle channels were observed in upstream locations, while step-pool channels, often bedrock controlled, were observed downstream. Pebble counts indicate substrate size tends to increase downstream in association with higher energy channel forms. Steeper tributary valleys draining mountain ridges are deeply entrenched possibly as the result of a large flood in 1979. While preliminary, results suggest channel geomorphology in Robins River is complex due to the influence of several factors including legacy and ongoing human impacts, increased hurricane frequency and intensity over the past several decades, karst processes, variable roughness of riparian vegetation, and long recovery periods for extreme flood effects.

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