The 6M approach to land subsidence

Abstract. Though global awareness of land subsidence has increased over recent years, subsidence remains an ongoing and largely unsolved problem, which is exemplified by frequent discoveries of apparently new subsiding areas. This means that for many of these areas there is a continuous and growing need to provide guidance to decision makers on how to tackle this global problem. This paper presents a comprehensive, step-by-step approach to address land subsidence, illustrated by best practise examples from around the world. The approach places emphasis on the long-term sustainability of resources, whose development is related to the subsidence problems. We identified 6 steps, collectively referred to as the 6M approach, that are crucial to tackle subsidence: Measuring, understanding Mechanisms, Modelling, Money, Measures and Monitoring. This paper offers guidance for implementing the 6M approach, and the lessons learned from the real-life examples provide valuable information and inspiration for decision makers and experts to address subsidence. The focus is on subsidence in deltaic and coastal areas where subsidence contributes to relative sea level rise. It is expected that the 6M approach will contribute to lowering the threshold to act on subsidence. The 6M approach is also used as a guiding principle for the thematic subdivision of TISOLS, providing a meaningful linkage between subsidence science and the societal response to subsidence problems.