Subsidence Trends of Volturno River Coastal Plain (Northern Campania, Southern Italy) Inferred by SAR Interferometry Data

Abstract

Abstract:The Volturno Plain is one of the largest alluvial plains of peninsular Italy, which is one of the most susceptible plains to coastal hazards. This area is characterized by both natural and human-induced subsidence. This present study is based on the post-processing, analysis and mapping of the available Persistent Scatterer interferometry datasets. The latter were derived from the combination of both ascending and descending orbits of three different radar satellite systems during an observation period of almost two decades (June 1992-September 2010). The main output of this study is a map of vertical deformation, which provides new insights into the areal variability of the ground deformation processes (subsidence/uplift) of Volturno plain over the last few decades. The vertical displacement values obtained by the post-processing of the interferometric data show that the Volturno river plain is characterized by significant subsidence in the central axial sectors and in the river mouth area. Moderate uplift is detected in the eastern part of the plain, whereas other sectors of the study area are characterized by moderate subsidence and/or stability. On the basis of the analyzed subsoil stratigraphy, we inferred that the subsidence recorded in the Volturno plain is mainly a consequence of a natural process related to the compaction of the fluvial and palustrine deposits that form the alluvial plain. The anthropic influences (e.g., water exploitation, urbanization) are substantially considered to be an additional factor that may enhance subsidence only locally. The uplift mapped in the eastern sector of the plain is related to the tectonic activity. The study of the subsidence in the Volturno plain is a valuable tool for river flood analyses and the assessment of the coastal inundation hazards and related risk mitigation.

Analysis and Classification of Natural and Human-Induced Ground Deformations at Regional Scale (Campania, Italy) Detected by Satellite Synthetic-Aperture Radar Interferometry Archive Datasets

“…The subsidence recorded in the Volturno plain is mainly a consequence of a natural process related to the compaction under the lithostatic load of the fluvial and palustrine deposits that form the alluvial plain. The magnitude of the recorded subsidence has been found to be greater when thick peat layers occur in the subsoil [18]. The anthropic influences (e.g., water exploitation and urbanization) is able only to locally increase the subsidence effect [18], while in some sectors the negative balance between the water recharge rates of the Volturno hydrographic basin and the drainage operated by the artificial channeling, related to industrial and intense agricultural activities [5,66], may have larger effects on subsidence rates.…”

“…Firstly, the regional scale annual average LOS velocity raster maps (vLOS asc -R and vLOS desc -R maps), referring to ascending and descending orbits of ERS-1/2, RADARSAT and ENVISAT PSI datasets, were produced by applying a spatial interpolation of the average velocity PS's point values with the Inverse Distance Interpolation Weighted (IDW) method. The IDW approach is commonly used to interpolate datasets formed by scattered points, thus allowing both reliable results and preservation of local variability of the data [17,18,[57][58][59]. In this study case, an interpolation method consisting of a quadratic weighting power of 2 within a 1000-m radius neighborhood was used to obtain 100-m regularly spaced grids, namely the ascending and descending LOS velocities raster maps derived from ERS-1/2, RADARSAT, and ENVISAT datasets with coherence > 0.65.…”

“…The subsidence of alluvial coastal plain can be considered as a natural process mainly due to the compaction of the alluvial sediments infill under the lithostatic load, and the anthropic influences due to water pumping and urbanization loads are only additional factors that locally enhance the subsidence effects [17,18]. In Volturno, Sarno, and Sele river plains urban areas the subsidence-induced ground displacements due to groundwater withdrawals have relevant consequences to the exposed facilities [63,64].…”

“…The uplift recognized in the eastern sector of the plain is related to the interplay between tectonic activity and hydrogeological conditions (Figure 9). The uplift can be due to the action of an E-W oriented active fault that bounds the area to the south [18]. Besides, the study area is characterized by a porous multi-layered aquifer system, formed by volcaniclastic and alluvial deposits, and the groundwater circulation can be considered unitary in the aquifer system.…”

Observing Geohazards from Space

“…Looking at a whole alluvial plain susceptible to land subsidence and coastal hazards, Matano et al [12] use almost two decades of InSAR information (1992-2010) derived from the ERS-1/2, ENVISAT and RADARSAT-1 C-band SAR missions to detect subsidence trends of the Volturno River Coastal Plain (Italy). The authors interpret and post-process six datasets of Permanent Scatterers InSAR (PS-InSAR) and Persistent Scatterer Pairs (PSP) results to derive maps of vertical deformation and identify significant subsidence rates in the central axial sectors and the river mouth area, and some uplift related to tectonic activity in the eastern part of the plain.…”