UNRAVELING HUMAN INFLUENCE ON THE GEOLOGY OF THE NETHERLANDS IN 3-D

The Dutch coastal and fluvial plains rank among the most anthropogenically affected terrains in the world in terms of both duration and intensity of their artificialization. This contribution reviews the extent to which human action is discernible in the Dutch subsurface; qualitatively in the country as a whole, and quantitatively in a representative study area of 100 km² in the coastal/fluvial plains east of the city of Rotterdam. Here, we compared the ages and volumes of natural and anthropogenic or human-influenced deposits, using geological, pedological, groundwater and environmental data, as well as national subsurface models.

The oldest major anthropogenic deposit in the study area is a post ~1000 AD clastic pulse, which represents the early stages of cultivation as well as the delayed delivery of sediment released by the onset of agriculture in the upstream Rhine catchment. The second one is artificial ground below settlements and infrastructure, (almost) all of which postdates the cultivation of the study area around 1200 AD and most of which will have been emplaced after World War II. Artificial ground makes up about 4% of the volume of all Holocene deposits, a share that compares with that of natural facies units such as channel belt deposits. Post mid-19^th century deposits are only found along the major rivers, delimited by the very dykes that suspended sedimentation in the remainder of the area. Because of that, the beginnings of the Industrial Age and the Atomic Age, each of which marks a significant increase of the human environmental footprint globally, have gone largely unrecorded. Land use and agro-industrial emissions of the post-WW2 era did however leave volumetrically significant imprints on soils and the hydrogeochemistry of quaternary aquifers.

Beyond an analysis of human influence on the physical, abiotic, environment, our study represents an attempt to incorporate the 'human factor' in 3-D geological modelling. This is a much-needed addition to our methods and products. Not only will it help us to better understand and characterize the urban subsurface. A better appreciation of influence on the subsurface should also stimulate us to better manage the subsurface, geological resources, and the environment in general.