Gullies and closed depressions in the loess belt: Scars of human–environment interactions

Abstract

This chapter illustrates how the study of the characteristics and spatial pattern of closed depressions (CDs) and several types of gullies in old forests may help unraveling human–environment interactions in (pre)historical times. The Meerdaal Forest in central Belgium, being continuously a forest for at least eight centuries and most probably already from the fifth century AD onwards, offers a unique opportunity to study such geomorphic features as it has very well conserved a pre-medieval landscape with 71 CDs and 252 gully channels. A systematic and detailed investigation of these geomorphic features, using process-based knowledge of soil erosion processes, reveals that these features result from a period with intense agricultural activities. The CDs are man-made features, most probably ancient quarries made to extract calcareous loess which was then used to lime nearby cropland on the flatter parts so as to improve its fertility. During high-magnitude rainfall events on these bare cropland areas that were cleared, sufficient runoff could then be produced to scour gully channels on sloping parts of the surrounding forest. Dating of both CDs and gullies in this old forest indicates that these features result from an agricultural land use phase between the eighteenth century BC and the third century AD. The gullies in Meerdaal Forest are rather unique as they are, to our knowledge, the only known gullies dating from the Roman period or before. These gullies teach us that intense soil erosion is not only an important soil degradation process occurring in recent times but that in historical times also periods with significant soil erosion have occurred. As such Meerdaal Forest is an important geomorphosite with a high geovalue.