Geomorphology and Sediment Dynamics of a Humid Tropical Montane River, Rio Pacuare, Costa Rica

摘要

Only a small body of work currently exists regarding the geomorphology of humid tropical montane rivers. The research that does exist reports rapid geomorphic processes and high sediment loads compared to other montane rivers. This research applies traditional field survey methods combined with new applications of remote sensing techniques to examine the geomorphology and sediment dynamics of the montane portions of the Rio Pacuare in Costa Rica. A suite of geomorphic components (channel slope and width, lateral contributions and planform) are examined and a model presented that illustrates the complexity of the Rio Pacuare’s geomorphology and how the distribution of alluvial sediment varies in relation to geology (tectonics and lithology) and flow hydraulics (stream power). Next, average annual bedload sediment transport capacity is estimated using fifty-one years of daily discharge data at six different locations within the study area, including the temporal (monthly) variability of sediment flux due to dry versus wet season discharge regimes. Then, a time-step hydraulic model is created that simulates observed (modern) and potential future discharge scenarios based on regional climate change model results. The simulated discharge data for two locations within the study area is then integrated into the sediment transport model to examine how sediment flux, and thus channel geomorphology, is likely to change in response to changes in the river’s discharge regime.