WOOD SALVAGE, LANDUSE AND ANTHROPOGENIC IMPACTS ON THE GEOMORPHOLOGY OF THE RIO BRAVO BELIZE, A LOWLAND TROPICAL FLUVIO-KARST RIVER: INTEGRATION OF LIDAR AND HYDROGRAPHIC DATA

Anthropogenic pressures, past and present, have impacted the geomorphic evolution of the Rio Bravo and its tributaries. In unprotected reaches of the Rio Bravo there is significant salvage of submerged in-channel wood for timber. Salvage of in-channel wood has been pointed to as an environmentally less destructive alternative to logging in threatened tropical forests, including those of Belize. However, we lack quantitative understanding of how tropical river systems respond to significant wood removal in relation to channel morphology, hydraulics, and habitat structure. Using the Rio Bravo as a case study, this preliminary research begins to characterize the natural wood dynamics and impacts of active wood salvage in this lowland tropical fluviokarst system. Here we present new data collected along the Rio Bravo, including bathymetry and channel geometry with down-nadir sonar, and in-channel wood concentrations with side-scan sonar. Additionally, we used an Acoustic Doppler Current Profiler to measure discharge, fine scale flow structures around in-channel wood, and suspended sediment load. This is integrated with channel planform data derived from a lidar DEM. These data show significant differences in wood distribution and channel morphology between protected reaches and those subject to wood salvage. However, it is difficult to disentangle the effects of wood salvage and other anthropogenic pressures such as deforestation and intensive agriculture. Future fieldwork will provide longitudinal data to refine these relative impacts.