A brief history of delta research

The first detailed map, based on field evidence, of the western part of the Rhine-Meuse delta was made by Vink (1926), figure 1. He realized that sand was deposited in the river bed, clay was deposited further away from the channel and peat was formed in remote flood basins. As a geography teacher he explored the delta during weekends by bike, using an iron rod to sense if there was sand in the ditches. A revised version of his map was published in 1954, shortly after his death (figure 2).

Figure 1 Detail of the map of the western part of the Rhine-Meuse delta by Vink (1926). Channel belts are shown in blue.
Figure 2 Detail of Vink's (1954) map, showing a wide channel belt in the Kromme Rijn area.

Vink believed that avulsions (shifts of river channels to other locations on the floodplain) did not occur in the Rhine-Meuse delta, and thought that all Holocene rivers existed simultaneously. In the course of the Holocene, an increasing number of channels were believed to have been abandoned.

In 1936, the first geological map of the Netherlands was published (figure 3) by the Geological Survey. This map was a huge step backward: it showed no channel belts, only isolated 'islands' of sand. Apparently, Vink's (1926) magnificent study was ignored, possibly because he was a geographer, and not a geologist.

Figure 3 Fragment of the geological map of the Netherlands (1936), showing the same area as in figure 2. Note that the channel belt has been mapped as several isolated 'islands' of sand, that bear little resemblance to the true shape of the channel belts that were previously mapped by Vink (1926).

In the period 1940-1960 various detailed and excellent studies were carried out by the 'Wageningen Agricultural University' under the supervision of Edelman. Most of these studies included detailed geogenetic soil maps. They were published in Dutch, and never received the international acclaim they deserved. Examples are the studies of Edelman et al. (1950), Pons (1957, 1966, figure 4), Hoeksema (unpublished, figure 5) and Egberts (1950). The Wageningen scholars later directed the 'Stichting voor Bodemkartering' (Soil Survey). Although the maps were excellent, they still lacked the sedimentological background that was gained in the Mississippi delta by Fisk (1947).

Figure 4 Detail of the map of Pons (1957) showing a braided river pattern in the Land van Maas en Waal (eastern river district). A meandering channel of Aller°d-interstadial age is seen in the northern part of the depicted area.
Figure 5 Detail of the map of Hoeksema (unpublished) of the Kromme Rijn area, southeast of Utrecht. Sand is shown in yellow and orange, clay in green. The map was hand-colored, and was never published.

A revolutionary new approach was chosen by the new geological map, scale 1:50,000, published by the Netherlands Geological Survey (Verbraeck 1970, 1984), figure 7. This map had a 'profile-type legend', which meant that the entire Holocene succession could be shown, and not just the deposits at the surface. Unfortunately, due to a low coring density (only 6 corings per km2) the map contained many mistakes, and wrong correlations. In addition it was shown by Berendsen (1982) that the presumed concept of synchronous sedimentation in the marine and 'perimarine' area, that was crucial to the map, was invalid, making it obsolete by modern standards (Berendsen 2004).

Figure 6 Detail of the soil map of Egberts (1950), showing many residual channels in the Over-Betuwe.
Figure 7 Detail of the geological map of the Rhine-Meuse delta (Verbraeck 1970). The map has a profile-type legend, allowing to describe the entire Holocene succession. However, the concept of the map was shown to be wrong.

Detailed geomorphological and geological maps were published by Utrecht University, from 1982 onwards, under the supervision of Berendsen (figure 8 and 9). These maps are based on numerous corings (50-300 per km2), carried out by students of physical geography, and include new sedimentological insights as well as results of 14C dating and archeological investigations.

Figure 8 Detail of the geomorphological map of Berendsen (1982), scale 1:25,000. Geomorphological units are subdivided based on lithological succession.
Figure 9 Detail of the geological map of the Bommelerwaard (Berendsen 1986). The map shows the succession of lithogenetic units to a depth of approximately 2 m below the surface. Yellow: channel belts; Green: flood basins; Blue: residual channels

Over the years, almost the entire Rhine-Meuse delta has been mapped (figure 10), based on more than 200,000 lithological borehole descriptions, 1300 radiocarbon dates and 45,000 dated archeological artifacts. Presently, the effort is concentrated on the IJssel valley and the westernmost part of the delta, to study the interaction of coastal evolution and fluvial dynamics.

Figure 10 Detail of the geological-geomorphological map of Berendsen & Stouthamer (2001) of the entire Rhine-Meuse delta, scale 1:100,000. This map shows the ages of Holocene channel belts (red= young, green = old). Enlarge

Modern mapping is greatly enhanced by the use of the AHN (Actueel Hoogtebestand van Nederland), a digital elevation model based on laser-altimetry, with previously unheard of accuracy (1 measurement per 5 m2). The AHN makes it easier to find the best coring locations, and often shows details that are not, or no longer, visible in the field (figure 11).

Figure 11 Digital elevation map (AHN) of the Zijderveld channel belt (Berendsen & Hoek 2005). This channel belt was erroneously mapped by Verbraeck (1970), as indicated by the thin black lines. The digital elevation map is available since 2004, and greatly enhances geological and geomorphological mapping. The picture shows the actual position of the channel belt as indicated by the white lines. The residual channel can be detected in the left picture and is shown in the right picture as a solid blue line. Enlarge

Literature

  1. Berendsen, H.J.A. (2004), Rivers and the sea: how science went wrong explaining the formation of the Netherlands' coastal plain. In: Dietz, T., P. Hoekstra & F. Thissen eds. The Netherlands and the North Sea. Dutch geography 2000-2004. KNAG: Netherlands Geographical Studies 325, p. 56-63.
  2. Berendsen, H.J.A. & E. Stouthamer (2001), Palaeogeographic development of the Rhine-Meuse delta, The Netherlands. Assen: Van Gorcum. 270 p.
  3. Berendsen, H.J.A. & W. Hoek (2005), Eindrapport van het fysisch-geografisch onderzoek in het kader van de verbreding van de A2. ICG-report 2005/02.
  4. Edelman, C.H., L. Eringa, K.J. Hoeksema, J.J. Jantzen & P.J.R. Modderman (1950), Een bodemkartering van de Bommelerwaard boven den Meidijk. Verslagen van Landbouwkundige Onderzoekingen 56.18. De bodemkartering van Nederland, deel 7, p. 1-137.
  5. Egberts, H. (1950), De bodemgesteldheid van de Betuwe. 's Gravenhage: Verslagen van Landbouwkundige Onderzoekingen 56.19. Serie: De bodemkartering van Nederland, deel 8, p. 1-82.
  6. Fisk, H.N. (1947), Fine Grained Alluvial Deposits and Their Effects on Mississippi River Activity. In Two Volumes. Corps of Engineers, U.S.Army. Waterways Experiment Station, Vicksburg, Mississippi.
  7. Pons, L.J. (1957), De geologie, de bodemvorming en de waterstaatkundige ontwikkeling van het Land van Maas en Waal en een gedeelte van het Rijk van Nijmegen. 's Gravenhage: Verslagen van Landbouwkundige Onderzoekingen 63.11, Ph.D. Thesis, Wageningen. Bodemkundige Studies 3.
  8. Pons, L.J. (1966), De Bodemkartering van het Land van Maas en Waal en een gedeelte van het Rijk van Nijmegen. Verslagen van Landbouwkundige Onderzoekingen 646, Wageningen: Pudoc. De Bodemkartering van Nederland, deel 22, Wageningen: Stiboka.
  9. Verbraeck, A. (1970), Toelichtingen bij de geologische kaart van Nederland, schaal 1: 50.000, blad Gorinchem Oost (38O). Haarlem: Rijks Geologische Dienst.
  10. Verbraeck, A. (1984), Toelichtingen bij de Geologische kaart van Nederland, schaal 1:50.000, bladen Tiel West (39W) en Tiel Oost (39O). Haarlem, Rijks Geologische Dienst.
  11. Vink, T. (1926), De Lekstreek, een aardrijkskundige verkenning van een bewoond deltagebied. Ph.D. Thesis, Amsterdam, H.J. Paris.
  12. Vink, T. (1954), De Rivierstreek. Baarn: Bosch en Keuning.