Where do you draw the line

Where do you draw the line

Land Subsidence

Land subsidence in South Holland: where do you draw the line?

How will the province of South Holland change in the next 10-100 years as a result of ongoing land subsidence, and where will problems arise? These are questions that the province, which has more than 3.5 million inhabitants, has to tackle. Pressure on space is increasing. More and more people want to live and work in South Holland, even though the subsurface is generally soft and unsuitable for building without inflicting damage. After 1000 years of land subsidence in South Holland, there are more and more places where the physical system is reaching the limit. Scenario studies have shown that continuing to use land as we do now will result in major costs. If there is no change in the policy, large areas will end up facing the same difficulties. In addition, ongoing subsidence results in rapidly-increasing management and maintenance costs for urban furnishings and infrastructure, including roads and pipes. A different approach and new measures are needed to keep the costs of living and working in South Holland manageable.

Our role in South Holland and the results

We teamed up with the province of South Holland to identify concrete plans to tackle land subsidence. Groundwater pressure is already so high in a few locations in South Holland that the top layer is heaving and cracking, and groundwater is forcing its way to the surface. This also leads to extra costs to keep the area suitable for living and working. The risk of heaving and cracking increases when the land subsides. That is why Deltares teamed up with the provincial authority, the water authorities, TNO and Wageningen Environmental Research to develop an action plan and to map out the risk of heaving and cracking. The map shows the future development of the risk of heaving and cracking as a result of peat oxidation in rural and urban areas. We are also providing key figures for heaving and cracking, and for salt seepage, and linking these phenomena to a rough cost estimate that can be used in any future study of social costs and benefits. An important subsequent step will be to identify possible action that the provincial authority can take in collaboration with stakeholders.

'We already knew that the risk of heaving and cracking was increasing due to peat oxidation but this study shows for the first time the level of risk in the future.
Gilles Erkens
Deltares expert land subsidence
A map showing the risk of heaving and cracking throughout the province will help policy officers and managers to determine the extent of the challenge and to identify areas they should focus on. This will allow us to determine the risks and to estimate the impact on the future of land use and the possible avenues open to land users.
Jan Strijker
Water policy advisor for the provincial authority of South Holland

For this project Deltares has collaborated with the following partners:

  • TNO
  • Wageningen UR
  • Provincie Zuid-Holland

Want to know more about this project?

Gilles Erkens
Expert land subsidence
  • +31 (0)88 335 7863