Disentangling subsidence: Towards a holistic approach

Abstract

Subsidence is a major global challenge with negative consequences for infrastructure, water management, and ecosystems. In many areas, the ground is sinking faster than the sea level is rising, which increases the relative sea level rise. This poses a burden on both the climate and society. Understanding subsidence is essential for sustainable land use and climate resilience. Climate change accelerates subsidence through drought, groundwater extraction, and permafrost melting. Conversely, subsidence contributes to climate change, such as through the emission of greenhouse gases from the oxidation of organic material in peat.Subsidence has both human and natural causes at various depths. Human-induced subsidence contributes the most in areas like deltas and coastal regions, such as in the Netherlands and Northern Italy. Causes include urban development, drought, groundwater extraction, and the extraction of oil, gas, and salt. These processes lead to the compaction of the subsurface, oxidation of organic matter and shrinkage of clay. Subsidence is measured as surface movement, capturing all the processes occurring beneath the surface. It is crucial to understand all the processes driving subsidence. This research discusses the causes of subsidence and how they can be modeled, as well as measurement methods such as satellite imagery. Mathematical and statistical models are used to calculate the relative and absolute contributions of different processes to total subsidence.This thesis includes a review of all subsidence processes, consequences, models, measuring and integration methods. The proposed holistic approach is applied in various regions, in the Netherlands in Almere, the Beemster Polder, Purmerend, the N31 south of Leeuwarden, and areas in Groningen and Rotterdam, and in Italy around the coastline of Ravenna. The results lead to improved understanding of subsidence in these regions, important for effective mitigation, and exhibit the flexibility of the method. The study emphasizes the importance of an integrated approach to effectively understand and address subsidence.