LIDAR-BASED HUMAN-ENVIRONMENTAL CONTRIBUTIONS TO LONG-TERM FLOODING AND LANDSCAPE CHANGE IN THE BELIZE-GUATEMALA TRANSBOUNDARY AREA

A combination of human activity and climate variability has affected the geomorphology of the Belize River Valley in western Belize since the Late Pleistocene, and these long-term factors still influence land use and flooding today. Using LiDAR, fieldwork, and lab analyses, we are quantifying to what extent human land use and associated erosion and aggradation of ancient Maya legacy sediments influenced geomorphic evolution and flood frequency. We are studying how these data can extend our record of flood recurrence, of great importance to contemporary flood risk, while also providing a useful analogue for modern landscape change. We used LiDAR to map the geomorphology of this river system and identify sampling sites in proximity to both Maya sites and relict river channels. Preliminary data from completed fieldwork shows evidence of large flood events that transported cobbles up to 52 cm in diameter, and particle size analysis indicates presence of non-local coarse sands that originated in the distant Maya Mountains. These flood sediments are intermingled with Maya activity layers, which we are dating from radiocarbon samples and artifacts. Magnetic susceptibility readings help confirm the presence of well-developed burned paleosols beneath cobble layers, showing the long-term human land use in this region. We are using a whole suite of further lab analyses to characterize the sediments, and correlating our emerging fluvial history with existing paleoclimate data and other environmental records. These data will help further differentiate human and environmental contributions to landscape change. Understanding the way these drivers may interact with each other to produce landscape change could offer important insight into modern environmental management and conservation, which is particularly relevant in the rapidly-developing, increasingly populated, tropics of Central America.