Applicability and effectiveness of structural measures for subsidence (risk) reduction in urban areas

Abstract. Managing subsidence and its impacts on cities in coastal and delta areas is a global challenge that requires comprehensive risk reduction policies, including both mitigation and prevention strategies. Urban areas often lack systematic methodologies for determining appropriate countermeasures. This paper proposes a twofold strategy for selecting subsidence reduction measures in urban areas – which refer to structural (i.e., technical) measures to prevent and mitigate subsidence and its physical consequences - based on their applicability and performance. The Question-and-Response (Q&R) system serves as a decision tree to identify suitable subsidence countermeasures based on their applicability to specific cases. Four indicators of  effectiveness – i.e.,  reduction potential, operational reliability, negative impact and service life – are then used to assess the performance of subsidence reduction measures. The proposed procedure was applied to 49 cases derived from a review of 52 scientific publications and additional expert sessions and surveys involving five academic scholars and 13 experts. Also, the method was applied to examples from Shanghai (China), Jakarta (Indonesia) and San Joaquin Valley (USA, California). The strategies proposed in this paper proved suitable for an initial screening of subsidence reduction measures applicable in different urban areas, after which a site-specific assessment can follow. Furthermore, this study shows the need to collect and share experiences in evaluating the performance of subsidence reduction measures more systematically, and gives a first framework to do so.