Our knowledge of the structure of the subsurface allows us to explain and predict subsidence. The Geological Survey of the Netherlands (GDN) advises on issues related to subsidence.

Predicting and explaining subsidence

Using our knowledge of physical processes in the shallow and deep subsurface, we create so-called  forward models that calculate subsidence. The composition of the subsurface plays a major role in this. Using  inverse modelling , we can also explain measured subsidence. In doing so, we are able to determine what part of the subsidence has been caused by land use and the extraction of groundwater (shallow causes) and what part has been caused by the production of oil, gas, and salt (deep causes). We subsequently use this quantitative explanation to draw up scenarios for the extent and location of potential subsidence resulting from activities in the subsurface. 

Advice to stakeholders

We use our calculations to support various authorities, such as water boards and provinces, as well as other stakeholders, such as private individuals and businesses. Our subsidence estimations enable (local) governments to formulate policy and make decisions. For example, on the starting or stopping of gas production. Or pumping more or less water from a polder.

Shallow causes

For various reasons, the origins of subsidence in the Netherlands can often be found in the shallow subsurface. After new land has been reclaimed, the soil settles as clay comes into contact with air. This process is known as clay shrinkage. Another cause of shallow soil subsidence is compaction, which is caused by changes in water pressure. This process is a frequent occurrence in the Netherlands when water is pumped out to keep farmland dry. And in peatlands, microorganisms (whose activity releases carbon dioxide from the soil) are the cause of soil subsidence. Clay ripening, compaction, and oxidation are largely irreversible processes. Shallow soil subsidence can damage above-ground infrastructure.

Deep causes

Besides shallow causes, mining also causes subsidence at greater depths, although to a much lesser extent. Salt production creates cavities that shrink under the pressure of the surrounding rock. During gas production, sand grains in the gas fields are compressed due to a drop in pressure. This radiates upwards, causing the soil to sink. Deep subsidence does not damage above-ground infrastructure since the subsided area (the so-called subsidence basin) is very large, often many kilometres in diameter.

Measurements as the foundation

We work with data from level indicators. These are fixed points on buildings in the Netherlands that Rijkswaterstaat uses to measure (with millimetre accuracy) the changing heights of locations in relation to each other every few years. On top of this, we use GPS measurements and radar satellite images taken every few weeks. 

Interested in more information? Contact Peter Fokker via the blue ‘mail directly’ button below.

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