Subsidence is a complex problem, both in a technical sense and in governance. This is particularly the case in the Netherlands, which is a low-lying and densely populated country where various causes of subsidence interfere with each other. Coping with subsidence in the Netherlands started already woo years ago. This long history of subsidence, however, along with its slow manifestation, has resulted in a tendency to adaptation rather than mitigation. There is a growing awareness that this focus on adaptation is actually excluding alternative solutions. Potentially cheaper or more effective options may be unknown and not even considered. At the same time, Dutch society is becoming more aware of the severity of human-induced subsidence as it is one of the most prominent current geological hazards. What is needed therefore, is a sound knowledge base facilitating the exploration of solutions outside the traditional way of thinking. Here we present the different knowledge and governance issues at stake. We start with the description of the natural processes that cause subsidence, and the human-induced causes like groundwater management and exploitation of deep geological resources. Then we elaborate how subsidence can be estimated from measurements. We pay specific attention to the utilization of modern ensemble-based techniques to integrate multiple models and data. The objective is to avoid deterministic predictions and instead produce a range of subsidence forecasts with confidence intervals that are in agreement with observational data and their uncertainties. Finally, we describe how technical knowledge can be integrated in decision making by estimating the costs and benefits of different scenarios, thereby offering an array of options for decision makers. Subsidence will keep playing a role in shaping the future of the Netherlands. Human-induced subsidence will continue with new subsurface activities directed towards the energy transition. Incorporating the grim sea level rise predictions, the issue becomes even more serious. It is therefore of paramount importance to maintain and further develop the current knowledge position and to develop proactive mitigation activities.

Understanding the geological and geotechnical characteristics of the shallow subsurface is crucial for engineering decisions in densely populated regions like the Netherlands. Urban areas are for a large part built on a complex stack of sand, clay, silt, gravel and organics that were deposited over the last hundreds of thousands of years under gradually subsiding tectonic conditions. One of these units, a fluvially deposited sand known as the Kreftenheye Formation, is widespread across the western part of the country and is vital for foundation design and groundwater dynamics. The Kreftenheye Formation is therefore well described by geotechnical and geological tests, yet integrating both types of data has rarely been done on a nationwide scale.

This paper focuses on 76 pairs of Cone Penetration Tests and boreholes that include Kreftenheye, out of a full database of nearly 200 pairs from TNO - Geological Survey of the Netherlands, generally reaching depths up to 40 meters. The study reveals significant spatial variations and depositional patterns within the Kreftenheye Formation, illustrating how overlying or interlayered flood plain or soft channel lag sediments influences the response of the CPT. Furthermore, CPT response and borehole samples have helped with making geological distinctions between the upper, Weichselian part of the Kreftenheye Formation and the lower Saalian part, showing how integrating both datasets can give both geological and geotechnical insights.