Jeroen Schokker

In: R.C.G.M. Lauwerier, M.C. Eerden, B.J. Groenewoudt, M.A. Lascaris, E. Rensink, B.I. Smit, B.P. Speleers and J. van Doesburg (Eds.) 2017. Knowledge for Informed Choices. Tools for more effective and efficient selection of valuable archaeology in the Netherlands.  Nederlandse Archeologische Rapporten 55.

In a geological GIS-data recombination project, a digital map was produced that contains information on the Netherlands’ former coastal and delta plain landscapes over the last 14,000 years: the Holocene and the very end of the Pleistocene. The polygon map product is accompanied by a set of palaeoDEMs (Digital Elevation Models) indicating the attention depth for buried land surfaces and aquatic deposits for four time slices. This paper provides conceptual background information on the legend and construction principles behind the polygon maps and the palaeoDEMs, i.e. the decisions taken during the making of. It also provides a basic overview of the map product: landscape structure, burial depth and preservation, visualised for the four time slices in the RCE’s Archaeology Knowledge Kit. The text links coastal plain buried landscape mapping for four time slices to the other Knowledge Kit activities described in this volume, notably that of the Archaeological Landscapes map (for the most recent  time slice in the coastal plain area of the Netherlands, and for all time slices in the Pleistocene uplands).

This paper presents method and first results of a study to quantify and communicate geotechnical risk for highway construction on soft soil and large building pits associated with infrastructural works in the Netherlands. A set of easy-to-read maps will inform the end users, geotechnical consultants at the Dutch Ministry of Infrastructure and Environment, in the early stage of projects of the most important subsoil-related geotechnical risks and their spatial distribution. The method involves risk identification, risk assessment, identification of critical geological features contributing to this risk, and development of maps reflecting the magnitude of the geotechnical risk. Geological information is derived from the detailed 3D geological model GeoTOP. GeoTOP allows quick data assessment and creation of maps on a regional to nationwide scale. Close cooperation between geologists, geotechnical engineers and end users is the key success factor in application of the method. Geotechnical consultants will use the maps to identify risks, determine early risk mitigation measures and design site-investigation schemes.

Abrupt climatic changes during Oxygen Isotope Stage 3 (OIS-3 or Weichselian Middle Pleniglacial) are revealed in the oxygen isotope records of the Greenland ice cores and in the North Atlantic marine cores. In the Greenland ice cores, these so-called D/O cycles start with a rapid warming of 5-10˚C within a few decades, followed by a phase of gradual cooling over

Abrupt climatic changes during Oxygen Isotope Stage 3 (OIS-3 or Weichselian Middle Pleniglacial) are revealed in the oxygen isotope records of the Greenland ice cores and in the North Atlantic marine cores. In the Greenland ice cores, these so-called D/O cycles start with a rapid warming of 5-10˚ C within a few decades, followed by a phase of gradual cooling over several hundred to more than a thousand years and often end with a final reduction in temperature back to cold, stadial conditions. On the adjacent European ...

This paper presents method and  first  results of a  study  to quantify and  communicate geotechnical risk for highway construction on soft soil and large building pits associated with infrastructural works in the Netherlands. A set of easy-to-read maps will inform the end users, geotechnical consultants at the Dutch Ministry of Infrastructure and Environment, in the early stage of projects of the most important subsoil-related geotechnical risks and their spatial distribution. The method involves risk identification, risk assessment, identification of critical geological features contributing to this risk, and development of maps reflecting the magnitude of the geotechnical risk. Geological information  is derived from the detailed 3D geological model GeoTOP. GeoTOP allows quick data assessment and creation of maps on a regional to nationwide scale. Close cooperation between geologists, geotechnical engineers and end users is the key success factor in application of the method. Geotechnical consultants will use the maps to identify risks, determine early risk mitigation measures and design site-investigation schemes.

Amsterdam is situated on the coastal-deltaic plain of the western Netherlands. Its geographical position brought the city prosperity, but also created huge challenges associated with heterogeneous and often adverse ground conditions. This paper explores the geology of Amsterdam to a depth of c. 100 m, based on the output of the 3D geological subsurface models DGM and GeoTOP. The model results are used to create a geological map of the area, to determine the extent and depth of the foundation levels that are in use for buildings in the city centre and to detect the source of filling sand on which part of the more recent expansion of the city was founded. It is shown that subsurface conditions have had a profound effect on both landscape development and historical city growth. Geomodels like DGM and GeoTOP provide an easily accessible way to obtain a better understanding of the shallow subsurface.

ABSTRACT Over the last ten to twenty years, geological surveys all over the world have been entangled in a process of digitisation. Their paper archives, built over many decades, have largely been replaced by electronic databases. The systematic production of geological map sheets is being replaced by 3D subsurface modelling, the results of which are distributed electronically. In the Netherlands, this transition is both being accelerated and concluded by a new law that will govern management and utilisation of subsurface information. Under this law, the Geological Survey of the Netherlands has been commissioned to build a key register for the subsurface: a single national database for subsurface data and information, which Dutch government bodies are obliged to use when making policies or decisions that pertain to, or can be affected by the subsurface. This requires the Survey to rethink and redesign a substantial part of its operation: from data acquisition and interpretation to delivery. It has also helped shape our view on geological surveying in the future. The key register, which is expected to start becoming operational in 2015, will contain vast quantities of subsurface data, as well as their interpretation into 3D models. The obligatory consultation of the register will raise user expectations of the reliability of all information it contains, and requires a strong focus on confidence issues. Building the necessary systems and meeting quality requirements is our biggest challenge in the upcoming years. The next step change will be towards building 4D models, which represent not only geological conditions in space, but also processes in time such as subsidence, anthropogenic effects, and those associated with global change.

Background, Aim and Scope - Coastal and river plains are the surfaces of depositional systems, to which sediment input is a parameter of key-importance. Their habitation and economic development usually requires protection with dikes, quays, etc., which are effective in retaining floods but have the side effect of retarding sedimentation in their hinterlands. The flood-protected Dutch lowlands (so-called dike-ring areas) have been sediment-starved for up to about a millennium. In addition to this, peat decomposition and soil compaction, brought about by land drainage, have caused significant land subsidence. Sediment deficiency, defined as the combined effect of sediment-starvation and drainage-induced volume losses, has already been substantial in this area, and it is expected to become urgent in view of the forecasted effects of climate change (sea-level rise, intensified precipitation and run-off). We therefore explore this deficiency, compare it with natural (Holocene) and current human sediment inputs, and discuss it in terms of long-term land-use options.

Materials and Methods - We use available 3D geological models to define natural sediment inputs to our study area. Recent progress in large-scale modelling of peat oxidation and compaction enables us to address volume loss associated with these processes. Human sediment inputs are based on published minerals statistics. All results are given as first-order approximations.

Results - The current sediment deficit in the diked lowlands of the Netherlands is estimated at 136 ± 67 million m3/a. About 85% of this volume is the hypothetical amount of sediment required to keep up with sea-level rise, and 15% is the effect of land drainage (peat decomposition and compaction). The average Holocene sediment input to our study area (based on a total of 145 km3) is ~14 million m3/a, and the maximum (millennium-averaged) input ~26 million m3/a. Historical sediment deficiency has resulted in an unused sediment accommodation space of about 13.3 km3. Net human input of sediment material currently amounts to ~23 million m3/a.

Discussion - As sedimentary processes in the Dutch lowlands have been retarded, the depositional system's natural resilience to sea-level rise is low, and all that is left to cope is human countermeasure. Preserving some sort of status quo with water management solutions may reach its limits in the foreseeable future. The most viable long-term solutions therefore seem a combination of allowing for more water in open country (anything from flood-buffer zones to open water) and raising lands that are to be built up (enabling their lasting protection). As to the latter, doubling or tripling the use of filling sand in a planned and sustained effort may resolve up to one half of the Dutch sediment deficiency problems in about a century.

Conclusions, Recommendations and Perspectives - We conclude that sediment deficiency – past, present and future – challenges the sustainable habitation of the Dutch lowlands. In order to explore possible solutions, we recommend the development of long-term scenarios for the changing lowland physiography, that include the effects of Global Change, compensation measures, costs and benefits, and the implications for long-term land-use options.

The Wadden Sea system along the south-eastern coast of the North Sea is one of the world's largest uninterrupted systems of barrier islands, tidal channels, tidal flats and salt marshes, where natural processes continue to function largely undisturbed. This highly dynamic system stretches over three countries from Den Helder in the Netherlands, through Germany, to Blåvandshuk in Denmark (Fig. 1).

TNO  - Geological Survey of the Netherlands (GSN) develops several subsurface models. Most of the published models are 'layer-based' models with national coverage, consisting of stratigraphical or hydrogeological layers with uniform properties. One of the models (GeoTOP) describes the upper 30m of the subsurface in millions of voxels (100 x 100 x 0.5m) each containing information on stratigraphy, lithology and the probability of occurrence for the different lithological classes. The GeoTOP modelling program was initiated in 2007 starting in the southwestern part of the Netherlands and has a regional approach, covering 13 areas. More than 90% of the available borehole data in DINO (a relational database containing ~525.000 bore holes maintained by GSN) is used and focus has been on the Holocene sequence, which has less detail in all other published models. Seven regions have been released covering around 55% of the country by the end of May 2016.

A key sedimentary unit from the northern Netherlands is the Saalian glacial till (in Dutch: “keileem”). Its shallow occurrence, lithological heterogeneity and relatively high hydraulic resistance make it an important unit to be considered in regional and local groundwater models. In 2013, TNO – Geological Survey of the Netherlands completed a new high-resolution 3D model of the glacial till, encompassing geometry, lithological composition and hydraulic resistance (Vernes et al., 2013). The high data density generally permits the till model to be used on a sub-regional to near-local scale.
Besides the direct application in the regional MIPWA groundwater model, the construction of the till model has resulted in several geologically relevant observations. This presentation discusses new insights regarding the geometry and heterogeneity of the Saalian glacial till. We show the exceptional variation in till depth and thickness over very short distances that was mapped in 3D for the first time at a regional scale, including the directionality present in the till geometry. Also, lithological variation of the till can now be studied over a range of local to regional scales. Furthermore, model construction has led to the spatial mapping of a second, older Saalian till in the south-east of Drenthe.

The Geological Survey of the Netherlands (GSN) develops several shallow subsurface models with regional to national coverage. The models are made publically available through the Survey’s web portal (www.dinoloket.nl). One of the models (GeoTOP) describes the subsurface in millions of voxels (100 x 100 x 0.5 m) each containing information on stratigraphy, lithology and the probability of occurrence of the different lithological classes. In addition to a range of academic applications that create new geological insights, GeoTOP is very suitable to create customized maps for our users. These maps are used for, amongst other applications, assessments of subsurface composition and properties such as consolidation or hydraulic conductivity, solving spatial planning issues or revealing geotechnical risks.

Relatively simple calculations on vertical voxel stacks in the model result in 2D raster maps, of which the design and information can be easily adapted to the user’s needs. The method is demonstrated using two examples: (1) a risk map for highway construction on soft soil linked to the risk of exceptionally slow consolidation. In this example, the geological information in the 3D model is translated to six risk categories displayed in a 2D map.; (2) a generalized soil composition map used by municipalities in estimating maintenance costs of their subsurface sewage-network. For this map the vertical succession of lithological classes in the upper 8 m of GeoTOP is summarized into five different map classes.

The maps from both examples show how smart selections and combinations of stratigraphy and lithological classes up to a chosen depth result in maps that are tailor-made to the user requirements. When needed additional maps can be created relatively easy, bringing geological information one step closer to the user’s own area of expertise.

In the near future we will incorporate more parameters in GeoTOP, making the model suitable for other applications. For the long term perspective we envision to create more flexible models; incorporating time (4D) and scaling. These models allow for, for example, detailed maps in urban areas and the creation of maps for a certain time period. With these perspectives the amount of information in the models increases rapidly, making tailor-made dissemination even more important.

In a geological GIS-data recombination project, a digital map was produced that holds information on the Netherlands’ former coastal and delta plain landscapes in the last 14,000 years: the Holocene and the very end of the Pleistocene. The end product polygon maps are accompanied by a set of palaeoDEMs indicating the ‘attention depth’ for buried land surfaces and aquatic deposits; both for four time slices. This paper provides conceptual background on legend and construction principles of the polygon maps and the palaeoDEMs (‘decisions during the making off’) and a basic overview of the map product (‘landscape structure’, ‘burial depth’, ‘preservation’), visualised for the four time slices of RCE’s Archaeological Knowledge Kit. The text links the coastal plain buried landscape mapping for time slices T0, T1, T2 and T3, to the other Knowledge Kit activities described in this volume, notably that of the Archaeological Landscape map (for time slice T4 in the coastal plain part of The Netherlands, for time slice T0 to T4 in the Pleistocene uplands)

The Schoonebeek oil field is one of the largest onshore oil fields in Europe and NAM has produced 250 million barrels of oil in the period 1947-1996. NAM recently re-opened the field using modern steam injection techniques. During this field trip we will visit the NAM Schoonebeek facilities. Prior to that, we will make several stops to study analogues of the field which is formed by a shallow marine sandstone. An equivalent of the reservoir rock is outcropping just 50 km south of Schoonebeek: the well-known Bentheimer sandstone. Additionally, along the Dutch coast west of Amsterdam shallow marine environments similar to the Schoonebeek reservoir are omnipresent as present-day and sub-recent (Holocene) environments and deposits.

The first stop on Saturday will be at the beach near the village of Camperduin. The present-day coastal sedimentary environment is well developed here. Subsequent stops will be more inland, to view the imprint of a sub-recent back-barrier inlet system on the present-day morphology. The shallow subsurface will be revealed using lacquer peels and shallow drillings. The remainder of the route to Bad Bentheim (Germany) will provide a cross section of several Quaternary depositional environments in the Netherlands, aided by the results of shallow geophysical techniques.

On Sunday the focus is on the Lower Cretaceous Bentheimer sandstone analogue. Outcrops in four quarries will show facies and thickness changes over relatively short distances. These are essential parameters for efficient development of an oil or gas field and for the development of geothermal doublets. The final stop will be at the location of the redeveloped Schoonebeek oilfield. On the way we will pass through the German part, the Emlichheim oilfield development. The new development strategy of NAM will be explained with reference to the subsurface model.