Managing Land Subsidence in the Netherlands: A Process-Based Modelling Approach to Evaluate Alternative Sustainable Pathways

The Netherlands confronts significant land subsidence challenges, primarily in the low-lying, densely populated soft soil regions. Land subsidence results from drainage or loading of the clayey and peaty shallow subsurface, extraction of groundwater or hydrocarbons, and local salt mining at deeper levels. These activities are compounded by natural subsidence processes such as local to regional tectonics, glacial isostatic adjustment, and autocompaction. The impacts of land subsidence are further exacerbated by global warming and rising sea levels. While Dutch institutions acknowledge the escalating economic costs of land subsidence (e.g. Van den Born et al., 2016), the prevailing land management practices, essential for current economic activities, contribute to a policy lock-in (Seijger et al., 2017), necessitating sustainable alternatives.

Our research aims to quantify explicitly the individual shallow processes of land subsidence (i.e. compression, peat oxidation) and establish their relative contributions using Atlantis, a process-based 3D land subsidence model integrated with the GeoTOP geological framework that represents the subsurface build-up and properties. This model serves as a tool for developing regional land subsidence projections up to 2100 across the Netherlands. By leveraging a combination of advanced local and regional observation data, including novel processed InSAR products, and recent findings from key national research initiatives like NWA-LOSS, NOBV, DeepNL, and Regiodeal Groene Hart, we gain a more refined understanding of subsidence processes which will be implemented in the model. Here we present the initial results of our approach by calculating the extent of human-induced shallow subsidence in the Netherlands for different future land subsidence scenarios. These scenarios were developed via a back casting method, encompassing extremes like no subsidence, minimal damage, and cessation of shallow drainage. We highlight the importance of combining numerical modelling with policy development methods such as back casting to test and evaluate optimal management pathways.

Building on previous land subsidence projections (Erkens et al., 2017), our approach integrates novel data and improved process understanding. A significant advancement of our study is the incorporation of an impact quantification module. This module translates the land subsidence projections (mm.yr^-1) and greenhouse gas emissions from peatlands (tonnes.yr^-1) into economic terms (EUR.yr^-1). This approach enables us to link the regional land subsidence to economic implications under various future projections. This tool could also help policymakers to gain insights via societal cost-benefit analyses to assess the socio-economic impacts of different adaptation and mitigation strategies.  This research is pivotal in exploring and finding alternative pathways on managing land subsidence in the Netherlands, therefore providing new perspectives on how to break the current policy lock-in. 

References

Erkens, G., Stafleu, J., and Van den Akker, J. J. H. (2017). Bodemdalingvoorspellingskaarten van Nederland, versie 2017, Deltares rapport klimaateffectatlas, 2017. 

Seijger, C., Ellen, G. J., Janssen, S., Verheijen, E., & Erkens, G. (2017). Sinking deltas: trapped in a dual lock-in of technology and institutions. Prometheus, 35(3), 193-213.

Van den Born, G. J., Kragt, F., Henkens, D., Rijken, B., Van Bemmel, B., and Van der Sluis, S. (2016). Dalende bodems, Stijgende kosten, Report Planning Agency for the Environment (PBL), report nr. 1064, 93 pp., 2016