Coastal subsidence detected by Synthetic Aperture Radar interferometry and its effects coupled with future sea‐level rise: the case of the Sele Plain (Southern Italy)

Abstract

The amount of coastal subsidence on the Sele River coastal plain has been examined and measured with local vertical land movement data. The vertical displacements, derived by satellite radar differential interferometry processing (Ps‐InSAR), show that the analysed coastal sector is characterised by a south‐eastward decrease of vertical subsidence rates. These results have been coupled with sea‐level rise (SLR) scenarios, in order to identify the most critical areas. In general, the subsidence mostly affects areas where alluvial deposits are thicker, the back‐dune areas and the Sele River mouth, all late Holocene in age. Five local SLR scenarios allow identifying zones in the plain potentially prone to inundation and the shoreline retreat for the years 2065 and 2100. For these dates, 2.2% and 7.06% of the investigated area will have a topography lower than the estimated future sea level. Moreover, results show that the extent of the areas potentially exposed to inundation and erosion increases moving from south to north.

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 ground deformation components and classification ( Figure 10) show that the coastal sector of the Sele Plain is characterized by a general westward horizontal deformation and a complex vertical pattern, validated by GPS surveys [17]. The northern and central sectors of the plain are characterized by relative subsidence rates of about −3 to −7 mm/yr along the coastline and by stability in the hilly inland area; around the Sele river mouth, a narrow area with subsidence rates up to −8 mm/yr is present, while the southern sector is characterized by general condition of stability with minor subsiding areas.…”

“…The vertical ground deformation pattern is correlated with the non-uniform stratigraphy of the coastal Quaternary infill because of the presence of layers of clastic sediments with different thickness and degrees of compaction in the two sectors. In detail, the subsidence is higher in the northern sector of the plain, where the Quaternary alluvial-coastal deposits are thicker because of the structural asymmetry of the graben, while in the southernmost sector the rates are the lowest recorded in the plain due to the minor thickness of Holocene deposits and to the presence of very thick sedimentary bodies of travertine [17]. These differences in ground deformation rates expose the northern and central sectors of the plain to higher levels of inundation and erosion hazard than in the southern sector [17].…”

“…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].…”

“…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 coastal subsidence phenomena are contributing to increasing the exposure of the subsiding low coastal areas to hazards related to inundation and erosion processes, and may cause a further increase in future relative sea level rates at local scale [17,65].…”