139 The role of the geological model in the analysis of land subsidence: a key lecture from the Volturno River alluvial plain (southern Italy) Carla Bufardi 1* , Marco Vigliotti 1 & Daniela Ruberti 1 1 Department of Engineering - University of Campania L. Vanvitelli, Via Roma, 9, 81031 - Aversa (CE), Italy. DR, 0000-0003-1471-9756; CB, 0000-0001-6039-4062; MV, 0000-0002-1709-442. Rend. Online Soc. Geol. It., Vol. 59 (2023), pp. 139-144, 4 fgs. https://doi.org/10.3301/ROL.2023.23 Short Note Corresponding author e-mail: carla.bufardi@unicampania.it Citation: Buffardi C., Vigliotti M. & Ruberti D. (2023) - The role of the geological model in the analysis of land subsidence: a key lecture from the Volturno River alluvial plain (southern Italy). Rend. Online Soc. Geol. It., 59, 139-144, https://doi.org/10.3301/ROL.2023.23. Guest Editor: Luigi Spalluto Submitted: 12 October 2022 Accepted: 17 February 2023 Published online: 02 March 2023 Copyright: © The Authors, 2023 ABSTRACT The present study focused on the relationships between subsidence and geological and geotechnical features of the Volturno River alluvial and coastal plain (northern Campania, Italy). Subsidence rates were determined through InSAR data analysis. A lithostratigraphic reconstruction was provided for the Holocene succession that overlay a continuous, thick, volcaniclastic unit (Campania Grey Tuf) deposited 39 ka B.P. The digital surface model carried out for this unit showed a palaeovalley morphology, allowing the reconstruction of the palaeodrainage network and a better modeling of the stratigraphic architecture of the post-CGT deposits. The subsidence map was overlain spatially with geological data. In the whole plain, the major ground deformations afect the sedimentary piles flling the palaeovalley engraved in the volcanic compaction-free basement. Inside the general subsidence trend, diferential compaction was detected within these deposits corresponding to the occurrence of clay and peat of diferent thicknesses, suggesting that the subsidence rates are due in part to the primary consolidation and in large part to the secondary consolidation. KEY-WORDS: Volturno River alluvial-coastal plain, subsidence, lithostratigraphic reconstruction, Holocene, Campania Grey Tuf. INTRODUCTION All over the word in the last decades, the river deltas and the relative alluvial plains are sinking, due to two main causes, often working together: i) sea level rise related to the climate change; ii) subsidence, both natural and anthropogenic. The latter phenomenon has many efects both on human life and environment, like the aquifer salinization, inundation of lowlands, coastal erosion and amplifed vulnerability to fooding and storm surges. The drivers of the subsidence are many, like the extraction of fuid, tectonics or isostatic adjustment and the chemical-physical changes of the deposits (Herrera-García et al., 2021). While much research in the coastal and delta areas has focused on the anthropogenic drivers of the phenomenon, few investigate the composition of the subsoil, consisting mainly of compressible deposits like sand, clay and peat, that in these environment are usually organic-rich and compact under their own weight (Long et al., 2006; Massey et al., 2006; Meckel et al., 2006, 2007; Shi et al., 2007; Tornqvist et al., 2008; van Asselen, 2011). The majority of the studies on compaction rates focuses on the frst meters of the subsoil, while only in a few analyses it is possible to fnd data about the whole Holocene sequence (Meckel et al., 2006; Tornqvist et al., 2008; Teatini et al., 2011; Higgins, 2016). The present study aims to provide a contribution to the understanding of the phenomenon through an insightful lithostratigraphic characterization, assessing the role of the sediments in ground deformation trends recorded for almost two decades (1992- 2010) in the alluvial coastal plain of the Volturno River (VR). The plain is located along the eastern coast of the Tyrrhenian Sea, in the north of Campania region (southern Italy; Fig. 1); it is a small part of the wide tectonic graben of the Campanian Plain, formed during the Quaternary and characterized, since the Late Pleistocene, by an intense volcanic activity that provided the massive deposition of pyroclastic products which contributed to the flling of the graben, together with fuvial and transitional-marine deposits (Santangelo et al., 2017). One of the last explosive eruption of the Campi Flegrei volcanic district, in particular, emplaced the Campania Grey Tuf deposits (CGT; ~39 Ky; De Vivo et al., 2001; Rolandi et al., 2020; Ruberti et al., 2020) that covered the whole plain with a thick, laterally continuous, volcaniclastic unit. These deposits constitute Special Issue - XIV Congresso GeoSed - Bari 2022