Elsevier

CATENA

Volume 172, January 2019, Pages 76-86
CATENA

Processes governing natural land subsidence in the shallow coastal aquifer of the Ravenna coast, Italy

https://doi.org/10.1016/j.catena.2018.08.019Get rights and content

Highlights

  • New insights into natural land subsidence processes in a shallow coastal aquifer

  • Interpretation of elastic, viscoelastic, and permanent components of land subsidence

  • Water table fluctuations control land subsidence at the daily-seasonal time scale

  • Elastic and viscoelastic components have different time periods (daily to seasonal).

Abstract

We identified the processes governing natural land subsidence in a shallow coastal aquifer near Ravenna (North eastern Italy) by analysing the relationships among different data set time series (water table level, rainfall, drainage, sea level, etc.) and establishing the correlations with vertical ground motion observed at a high-resolution settlement gauge. For the first time we establish the relationships between water table fluctuations and vertical displacement in a real field dataset as well as demonstrate the important contribution of primary consolidation and aquifer stratigraphy to natural land subsidence. Our study highlights the presence of three deformation components related to different processes controlling land subsidence: elastic, delayed-elastic, and irreversible (plastic) components. The elastic and delayed-elastic components are closely related to water table fluctuations that change the effective stress in two portions of the coastal aquifer at a daily (in the sandy unconfined portion) and seasonal time scales (in the finely layered clay-rich semiconfined prodelta portion), respectively. The irreversible component represents the trend in the land subsidence time series and is due to primary consolidation (pore water pressure dissipation) of the fine-grained prodelta levels above where the settlement gauge is located. The amplitudes of the elastic component can be up to 0.2–0.3 mm whereas the amplitude of the delayed-elastic component reaches 0.89 mm. The primary consolidation rate of deformation is 0.9 mm/year and constrains the likely age of prodelta sediments deposition to 1300–2800 years before present. The average degree of consolidation for the prodelta sediments varies from 0.8 to 0.99 according to consolidation coefficients varying from 1.58 to 3.15 m2/year, which are accepted values in the literature. Our analysis point out that primary consolidation in the shallow fine-grained sediments of the shallow coastal aquifer is still ongoing. The delayed-elastic land subsidence rate has similar magnitude to that due to primary consolidation and is likely connected to poroelastic effects in the prodelta sequence following seasonal variations in water table. Our findings are important for planning land subsidence management and monitoring strategies especially where the surface aquifer structure is heterogeneous due to different depositional settings.

Introduction

Subsidence is one of the most diverse forms of downward settling of the ground with little horizontal movement, ranging from small or local collapses to broad regional lowering of the earth surface. It is a global problem and the principal causes are aquifer-system compaction (Sneed and Galloway, 2000), dewatering (oxidation) of peat or organic soils (Grzywna, 2017; Zanello et al., 2011), underground mining (Dong et al., 2015; Ishwar et al., 2017), hydrocompaction and sinkholes (Psimoulis et al., 2007; Yechieli et al., 2016), crustal deformation, withdrawal of fluids (groundwater, hydrocarbons, geothermal) (Donaldson et al., 1995), and thawing permafrost (Liang et al., 2006).

The relationships between land subsidence and fluid withdrawal from deep confined aquifers is extensively described in the literature (Corapcioglu, 1984; Domenico and Mifflin, 1965; Galloway et al., 1999; Poland and Davis, 1969; Schmidt and Bürgmann, 2003; Sun et al., 1999) and many analytical (Calderhead et al., 2011; Liu and Helm, 2008; Tarn and Lu, 1991) and numerical modelling (Baú et al., 2004; Galloway and Burbey, 2011; Gambolati et al., 1996) studies were done to identify the physical processes involved. Natural subsidence processes connected to the compaction of sediments or tectonic phenomena were also extensively treated in the literature (Amelung et al., 1999; Gambolati and Teatini, 1998; Gambolati et al., 1999; Carminati et al., 2003). On the other hand, very few studies consider the relationships between water table fluctuations and natural land subsidence (Chang et al., 2004; Strack et al., 2008). To the best of our knowledge, no high-resolution continuous time series of land subsidence and water table levels were ever presented and interpreted in the literature.

By using data from a high-resolution settlement gauge, our present work aims to define the processes governing shallow ground settlement (magnitude and development over time since the installation of the instrument) and verify land subsidence and water table fluctuations interactions in the shallow coastal aquifer of Ravenna. Our work highlights the contribution of natural processes such as primary consolidation (compaction of sediments under their own weight via expulsion of interstitial pore water) and water table fluctuations in the Holocene shallow coastal aquifer of Ravenna to the cumulative land subsidence rate observed in the area (Bertoni et al., 1995; Teatini et al., 2005; Baldi et al., 2009). The processes in the shallow coastal aquifer are uncoupled from other processes contributing to the cumulative land subsidence rate and that are primary and secondary consolidation of deep aquifers (Teatini et al., 2011), fluids extraction from reservoirs (Teatini et al., 2006), tectonism, and isostasy (Carminati et al., 2003). The methodology we used includes the decomposition of data time series (subsidence-settlement, water table level, precipitation, drainage, sea level) into the trend, seasonality and noise components and find correlation coefficients between each analyzed component, especially between settlement and changes in water levels. Analytical solutions are also applied to model the irrecoverable and elastic components of land subsidence.

Section snippets

Study area

The area addressed by the present study includes the coastal area of the Ravenna city, in the Emilia-Romagna coastland, south of the Po River Delta (Northeastern Italy, Fig. 1). It is a lowland coastal area not exceeding 2 m above sea level (a.s.l.), with a large portion below mean sea level, because of the combined effects of natural and anthropogenic land subsidence, land reclamation, and sea level rise. In the study area, the trend in sea level rise during the time period 1990–2011 was

Time series analysis

Daily and monthly correlation coefficients calculated for time series dataset are listed in Table 2 and Table 3 as supporting information. The time series data for the most relevant (and correlated) parameters recorded (settlement [mm], water table level [m], drainage [mm], sea level [m]) are shown in Fig. 4. The results of the decomposition of the settlement daily time series are presented in Fig. 5a, b, and Fig. 6. Fig. 5a represents the seasonal component of the settlement, water table level

Discussion

The data we present and the methodology used help to constrain the processes contributing to natural land subsidence in the shallow coastal aquifer of Ravenna, which suffered extreme anthropogenic land subsidence in the past century because of gas and water exploitation (Bertoni et al., 1995; Teatini et al., 2005). This is important, because it allows to separate and quantify the effects of natural processes (primary consolidation, water table fluctuations, etc.) in the recently deposited

Conclusions

The natural land subsidence rate in the Holocene sediments of the shallow coastal aquifer of Ravenna (North eastern Italy) measured in this study accounts for 10–20% of the total land subsidence rate observed in the Ravenna area (10–20 mm/year).

Modelling and time series analysis of natural land subsidence and water table fluctuations (as well as parameters such as rainfall, drainage, and sea level) highlights three deformation components connected to the vertical ground motion: an elastic, a

Acknowledgments

The authors would like to thanks the IGRG Lab people (Integrated Geosciences Research Group) of the University of Bologna for the help during the field work activities and the Carabinieri for Biodiversity, Punta Marina Office, who allowed the access to the protected natural areas where the instruments were installed.

References (78)

  • E.L. Lewis et al.

    The practical salinity scale 1978: conversion of existing data

    Deep-Sea Res.

    (1981)
  • Z.-J. Luo et al.

    Finite element numerical simulation of land subsidence and groundwater exploitation based on visco-elastic-plastic Biot's consolidation theory

    J. Hydrodyn.

    (2011)
  • N. Phien-wej et al.

    Land subsidence in Bangkok, Thailand

    Eng. Geol.

    (2006)
  • P. Psimoulis et al.

    Subsidence and evolution of the Thessaloniki plain, Greece, based on historical leveling and GPS data

    Eng. Geol.

    (2007)
  • Xiaoqing Shi et al.

    Regional land subsidence simulation in Su-Xi-Chang area and Shanghai City, China

    Eng. Geol.

    (2008)
  • K.H. Xie et al.

    Analytical solutions of one-dimensional large strain consolidation of saturated and homogeneous clays

    Comput. Geotech.

    (2004)
  • W. Zhou et al.

    Remote sensing of deformation of a high concrete-faced rockfill dam using InSAR: a study of the Shuibuya Dam, China

    Remote Sens.

    (2016)
  • F. Amelung et al.

    Sensing the ups and downs of Las Vegas: InSAR reveals structural control of land subsidence and aquifer-system deformation

    Geology

    (1999)
  • A. Amorosi et al.

    Sedimentary response to late Quaternary sea-level changes in the Romagna coastal plain (Northern Italy)

    Sedimentology

    (1999)
  • A. Amorosi et al.

    Facies architecture and Latest Pleistocene-Holocene depositional history of the Po Delta (Comacchio Area), Italy

    J. Geol.

    (2003)
  • M. Antonellini et al.

    Groundwater freshening following coastal progradation and land reclamation of the Po Plain, Italy

    Hydrogeol. J.

    (2015)
  • G. Artese et al.

    Monitoring of land subsidence in Ravenna Municipality using SAR – GPS techniques: description and first results

  • D. Baú et al.

    Surface flow boundary conditions in modeling land subsidence due to fluid withdrawal

    Ground Water

    (2004)
  • W. Bertoni et al.

    Land subsidence due to gas production in the on- and off-shore natural gas fields of the Ravenna area, Italy

    IAHS AISH Publ.

    (1995)
  • A. Bonaduce et al.

    Sea-level variability in the Mediterranean Sea from altimetry and tide gauges

    Clim. Dyn.

    (2016)
  • A. Brambati et al.

    The lagoon of Venice: geological setting, evolution and land subsidence

    Episodes

    (2003)
  • E. Carminati et al.

    Apennines subduction-related subsidence of Venice (Italy)

    Geophys. Res. Lett.

    (2003)
  • I. Cerenzia et al.

    Historical and recent sea level rise and land subsidence in Marina di Ravenna, northern Italy

    Ann. Geophys.

    (2016)
  • P. Ciavola et al.

    Impact of storms along the coastline of Emilia-Romagna: the morphological signature on the Ravenna coastline (Italy)

    J. Coast. Res.

    (2007)
  • M.Y. Corapcioglu

    Land subsidence — a. a state-of-the-art review

  • M.Y. Corapcioglu et al.

    Viscoelastic aquifer model applied to subsidence due to pumping

    Water Resour. Res.

    (1977)
  • B.M. Das

    Principles of Foundation Engineering

    (1990)
  • P.A. Domenico et al.

    Water from low-permeability sediments and land subsidence

    Water Resour. Res.

    (1965)
  • E.C. Donaldson et al.

    Subsidence Due to Fluid Withdrawal

    (1995)
  • S. Dong et al.

    Spatio-temporal analysis of ground subsidence due to underground coal mining in Huainan coalfield, China

    Environ. Earth Sci.

    (2015)
  • A. Freeze et al.

    Groundwater

    (1979)
  • D.L. Galloway et al.

    Review: regional land subsidence accompanying groundwater extraction

    Hydrogeol. J.

    (2011)
  • D.L. Galloway et al.

    Detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar, Antelope Valley, Mojave Desert, California

    Water Resour. Res.

    (1998)
  • D.L. Galloway et al.

    Land Subsidence in the United States

    (1999)
  • Cited by (26)

    • The influence of groundwater levels on land subsidence in Karaman (Turkey) using the PS-InSAR technique

      2022, Advances in Space Research
      Citation Excerpt :

      As a result of population increases, cultivation of non-native or unsuitable crops in an area, and the unconscious attempt to supply groundwater to meet irrigation and drinking water needs in cities that lack adequate pumping and precipitation, water use has become a growing problem worldwide. Therefore, land subsidence events caused by excessive groundwater depletion have been widely recognized in recent decades, such as in the USA (Amelung et al., 1999; Buckley et al., 2003; Morton et al., 2006; Galloway and Sneed, 2013; Budhu and Adiyaman; 2013; Faunt et al., 2016; Peng et al., 2022), Mexico City (Osmanoǧlu et al., 2011; Cigna et al., 2012; Pacheco-Martínez et al., 2013; Castellazzi et al., 2016; Du et al., 2019; Cigna and Tapete, 2021), Iran (Mousavi et al., 2011; Motagh et al., 2008; Mahmoudpour et al., 2016; Foroughnia et al., 2019; Babaee et al., 2020), China (Zhu et al., 2015; Chen et al., 2020; Liu et al., 2021), Indonesia (Abidin et al., 2011; Gumilar et al., 2021), Nigeria (Cian et al., 2019; Ikuemonisan and Ozebo, 2020), Italy (Teatini et al., 2005; Antonellini et al., 2019), and many other countries (e.g., the UK, Egypt, Australia, France, India, Germany, Japan, Poland, Netherlands, Sweden, and the Saudi Arabia) (Liu et al., 2018; Bagheri-Gavkosh et al., 2021). The phenomenon of land subsidence may cause environmental harm through damage to infrastructure, ground surface ruptures, increased exposure to flooding, and negative socio-economic impacts on human life through loss of life and property (Ahmed et al., 2020).

    • Multi-technique geodetic detection of onshore and offshore subsidence along the Upper Adriatic Sea coasts

      2022, International Journal of Applied Earth Observation and Geoinformation
      Citation Excerpt :

      Indeed, the regional tectonic component, which is quite constant over the investigated area (Gambolati and Teatini, 1998, Pezzo et al., 2020) was significantly minimized by setting the reference system in Ravenna city. Another important contribution comes from the consolidation process of the Holocene sediments of the shallow coastal aquifer which has been estimated to account for 10–20% of the observed land subsidence (Antonellini et al., 2019). Ancillary data (i.e., gas production and groundwater withdrawal) provide additional information about causes and evolution over time of the phenomenon.

    • GIS-based soil maps as tools to evaluate land capability and suitability in a coastal reclaimed area (Ravenna, northern Italy)

      2021, International Soil and Water Conservation Research
      Citation Excerpt :

      The studied coastal area is located in the North-eastern Italy, and is bounded to the North and South, respectively, by the last stretch of the Reno River and the Lamone River, to the East by the Adriatic Sea and to the West by the eastern edge of the Comacchio Valleys (Fig. 1). The area has a total surface of 3488 ha, it is in plain and it is characterized by alluvial deposits that totally or partially buried the pre-existing brackish marshes and dune cords of Adriatic Sea (Antonellini et al., 2019; Ciavola et al., 2007). Most of the area is subjected to subsidence and it underwent reclamation between the end of the 19th and the beginning of the 20th century (Carbognin & Tosi, 2005; Zerbini et al., 2005).

    • Development of a coastal vulnerability index using analytical hierarchy process and application to Ravenna province (Italy)

      2020, Ocean and Coastal Management
      Citation Excerpt :

      It is a microtidal area, with mean neap tidal range of 30–40 cm and mean spring tidal range of 80–90 cm (Armaroli et al., 2012). Along with reduced river sediment supply, mainly due to the land use changes in the river basins, dam construction, flood control works and extensive bed material mining (Preciso et al., 2012), the major causes of coastal erosion are dune destruction, disruption of longshore sediment transport by harbours and piers, land subsidence (Teatini et al., 2005; Taramelli et al., 2015; Perini et al., 2017; Antonellini et al., 2019) and marine storms. Land subsidence along the Ravenna coastline is one of the most significant along the regional coastal area (up to 20 mm/yr, Perini et al., 2017).

    • On the link between soil hydromorphy and geomorphological development in the Cerrado (Brazil) wetlands

      2019, Catena
      Citation Excerpt :

      Thus, the boundary between Ferralsol and Gleysol is subject to highly contrasting dry and wet conditions and is therefore sensitive to structural changes (i.e., cracks and loss of pedality) and chemical dissolution (i.e., deferrugination) below the average depth of the water table. Lucas and Chauvel (1992) and Antonellini et al. (2019) both showed the link between water table fluctuations and natural land subsidence. The strain factor normalized by T1P1 confirmed that the chemically-driven collapse of T1P2 and T1P2J was due to chemical transfer (Table 4 and Fig. 6).

    View all citing articles on Scopus
    View full text