Land-cover change from forest to agriculture is widely recognized as a primary cause of accelerated soil erosion. Floodplains in agricultural watersheds represent fluvial archives for understanding anthropogenic erosion and downstream sedimentation. These agricultural legacy sediments may be used to construct watershed sediment budgets and can help reveal pathways of hydrologic and sedimentologic connectivity. However, the timing, spatial distribution, and feedback mechanisms of sediment transfers from slopes to floodplains are strongly scale-dependent, and there are limited field settings in which agricultural land-use has remained consistent over centennial timescales.
Hedgerow-defined agricultural landscapes in southwestern Czech Republic provide an opportunity to extend our understanding of human-induced erosion beyond decades to centuries. Floodplain sediments in the study area represent suitable archives for interpreting landscape-scale environmental changes associated with early agricultural land clearance (c. 1300 CE). X-ray florescence spectroscopy reveals changes in minerology and geochemistry that can be correlated with human activity. Pollen analysis also provides a mechanism for fingerprinting anthropogenically-derived sediments. Floodplains of small, medium, and large watersheds all contain fluvial sediment corresponding to the 14thcentury episode of intensive deforestation, but none of these fluvial archives reflect dramatic changes in sedimentation rates or processes. Detailed analysis of hillslope source areas using electrical resistivity tomography and high-resolution photogrammetry helps quantify the sediment trapping capabilities of field-boundaries. As a consequence of the landscape-scale field pattern established over 700 years ago, hillslopes have been largely de-coupled from downstream floodplain sinks. From a geomorphologic and pedologic perspective, this multi-functional landscape serves as a potential model for sustainable agricultural land management over centennial timescales.
J. Michael Daniels, Ph.D.
Department of Geography and the Environment
University of Denver