The sea clay landscape

The sea clay landscape covers the coastline of the northern Netherlands and southwestern Netherlands. Sea clay is a deposit of sea in the form of sludge. That is why it occurs in the coastal areas. Sea clay is very fertile, so suitable for arable farming.

Old country and new country

If we want to divide the landscape in the southwest of the Netherlands, a separation between oldland and newland will arise. Nowadays we call this old and recent sea clay polders. This dichotomy was achieved by soil research around the Second World War. The area covers almost the whole of Zeeland, to the Westland and the Biesbos. Oldland polders are lower than newland polders. This is because the sea no longer influences the oldland polders, but does influence the newland polders. The deposition of the sea ensures that the polders are still rising. Oudland polders were provided with protection against the sea, such as dams and dikes, at an early stage. Thus the influence of the sea has long since stopped.


Terpen, in Groningen they call it a wierde. Terpen was created because people wanted to protect themselves against flooding. First they served as an escape hill, but often changed into residential hills. Houses were built and the buildings were sometimes extended to entire villages. Terpen was created by storing manure and / or waste, which caused an increase in the land. The moment the water got too high, people were safe. The highest mound in the Netherlands is located in Hogebeintum. This mound is 8.80 m above sea level. We distinguish terpen in: handselterp, radialeterp and rectangular terp. Many mounds were lost in the 19th century. It was discovered that the soil of the mounds was good to use for nutrient-poor soils. By scattering the soil over nutrient-poor soils, it boosted the yield of the land.

Salt marshes and creek ridges

We find salt marshes on the coast near Groningen and Friesland. We also find them in Zeeland, but we call it salt marsh there. A salt marsh is overgrown with salt-loving plants, such as salicornia. In a salt marsh there are a number of channels where the water remains. We call this creeks. When the flood is over, a salt marsh is completely submerged. The moment the salt marsh floods, the sea leaves behind sediment (clay). When the sea recedes, this sediment remains. The sediment is in fact retained by the plants on the salt marsh. The salt marsh is becoming wider and wider, because the deposit on the salt marsh at normal water level can no longer take place. If the salt marsh is no longer flooded, the sand remains in the creeks and accumulates. The peat that lies beneath the sea clay sounds and so the sand gets higher. We call this creek ridges.

Twentieth century

The sea clay landscape, as it originally looked, with Terpen, winding roads etc. For a large part is no longer there. The expansion of agriculture, for example land consolidation and new land development, have ensured that the old cultural landscape has largely disappeared. New agricultural products, such as corn, ensure that the view of the landscape is obstructed. In addition, villages were constantly expanding, creating new roads and flattening the landscape.

Video: Polymer clay landscape boundary waters (February 2020).

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