Elsevier

Ecological Engineering

Volume 67, June 2014, Pages 223-237
Ecological Engineering

A retrospective assessment of the hydrological conditions of the Samborombón coastland (Argentina)

https://doi.org/10.1016/j.ecoleng.2014.03.081Get rights and content

Abstract

Coastal wetlands are transitional zones that play an important role as buffers between the land and sea in several ways, such as protecting the land from storm surge and reducing the input of nutrients from surrounding watersheds to the sea. Understanding the influence of human activities on the hydrological conditions of coastal wetlands is of paramount importance for preserving the ecological function and biodiversity of these unique ecosystems. In the last century, the Samborombón coastland (Argentina), which is an extensive intertidal wetland, has been affected by hydraulic projects and human activities. In this study, through a retrospective assessment of the hydrologic conditions, we show the impacts of channelization, embankments and mining on the surficial and groundwater hydrology of the Samborombón wetlands. The results indicate that channelization has promoted tidal flooding and seawater encroachment along the channels. The embankments have separated large areas from the estuary tides; during heavy rainfalls, they act as obstacles and cause the inundation of inland regions while allowing the accumulation of sodium chloride by saltwater evaporation after tidal overtopping events. The freshwater resources in the aquifer of the paleo-coastlines have been seriously damaged by mining of the shell ridges. The halophyl vegetation in the marshlands and the native forest of the shell ridges, which depend on tidal flow and fresh water, respectively, have been threatened. Nevertheless, although the hydrology of the Samborombón coastland has undergone changes, the engineering projects did not permanently modify or damage the surrounding ecosystems. The outcomes of this study will be useful for remediating ecosystems that have been impacted by human activities by following the fundamentals of ecological engineering.

Introduction

Coastal wetlands are highly dynamic environments that act as transitional areas between the land and the sea and are governed by continental and marine processes. Estuarine wetlands are exposed to frequent natural fluctuations and alterations. They are periodically inundated by high tides and storm surges as well as being flooded during intense rainfall. In coastal wetlands, marine and continental waters are exchanged and surface water and groundwater are mixed to form complex spatially and temporally variable systems (e.g., Tóth, 1963, Werner and Lockington, 2006, Robinson et al., 2007, Wolanski, 2007, Cao et al., 2012, Werner et al., 2013). Groundwater seeps from the land to the sea and seawater intrudes into coastal aquifers. In estuarine wetlands, the mixing of seawater and groundwater depends on the regional geo-morphologic characteristics of the coast, including ground elevation, soil texture, subsoil heterogeneity and climatic conditions (e.g., Sophocleous, 2002, Rizzetto et al., 2003, Pousa et al., 2007, Teatini et al., 2011, Braga et al., 2013a, Braga et al., 2013b, Day et al., 2013). Hydrological processes in such areas are often highly influenced by human activities, such as the overexploitation of natural resources, land reclamation, hydraulic projects and urbanization. These processes hasten salt contamination, land degradation, pollution and subsidence, which cause serious damage to soils and freshwater resources and threaten the ecological system. For example, urbanization, industry and port activities have greatly affected the environmental quality of Santos Bay (Brazil), resulting in severe sediment contamination and water pollution (Zanardi Lamardo et al., 2000, Abessa et al., 2005, Magalhães et al., 2012). In the Yangtze River Estuary (China), engineering projects, such as the construction of a dam and a deep-water navigation canal, have caused many hydrodynamic modifications (Yang et al., 2005, Tang et al., 2011, Zhang et al., 2013), while urban development and industrial growth have caused the deterioration of surface water quality (Ren et al., 2003). The Han River Estuary (South Korea) has undergone changes in water dynamics and chemistry due to engineering projects, such as the construction of submerged dams (e.g., the Singok and Han River dams), which have significantly decreased freshwater outflow to the open sea (Park, 2004, Yoon and Woo, 2013). In the northern Adriatic coast of Italy, the overexploitation of subsurface fluids during the 20th century, especially during the 1960s and 1970s, was responsible for regional subsidence. The decrease of ground elevation produced a significant retreat of the coastline, erosion of salt marshes and tidal flats, increased the frequency of flooding in lowlands and historical cities such as Venice and Ravenna (Carbognin and Tosi, 2002, Amos et al., 2010 and references therein) and worsened the saltwater contamination of shallow aquifers and farmlands (e.g., Carbognin et al., 2009, Viezzoli et al., 2010).

Understanding the influence of humans on the hydrologic conditions of transitional coastal environments is of paramount importance because of the widely recognized buffering functions of these unique transitional ecosystems for biodiversity and valuable economical resources such as agriculture and fisheries. This issue is also essential for planning the correct restoration of ecosystems that have been substantially disturbed by human activities and for guiding environmental adaptation in a changing climate. In this sense, ecological engineering, which is defined as the design of sustainable ecosystems that integrate human society with the natural environment for the benefit of both, has to be developed (Mitsch, 2012, Cheong et al., 2013).

Samborombón Bay, which is an extensive intertidal wetland that was declared a RAMSAR site in 1997, is located on the Argentinean side of the outer estuary of the Rio de la Plata (Fig. 1). The bay extends for 180 km (224,000 ha) and receives the Samborombón River from the northwest, the Salado River from the west and the Ajo River from the south. Lowlands and marshlands are present behind extensive salt marshes and muddy tidal flats. They are frequently flooded by tides and storm surges from the Atlantic Ocean, but the most significant damage to socio-economic development often results from heavy rain on the coastal plain. For this reason, several natural and artificial canals have been constructed to drain the bay's low hinterland.

The world's major estuarine wetlands are subject to economic development and social transformations that exert great pressure to exploit natural ecosystems and trigger changes in the hydrodynamics and hydrochemistry of the water resources. Unlike many of the world's estuaries that are heavily populated and industrialized, Samborombón Bay contains only small urban and built-up areas. The socio-economic development is mainly associated with livestock farming and mining. Nevertheless, several engineering and hydraulic projects have been constructed over the last century without assessing the anthropogenic impact on the hydrology of the coastal wetlands. The hydrological studies that have been carried out in the area have focused on the aquatic communities of the Río Salado basin (e.g., Conzonno et al., 2001, Gabellone et al., 2008, Rosso, 2008), estuary dynamics (e.g., Guerrero et al., 1997, Simionato et al., 2004, Acha et al., 2008), the hydrodynamics and hydrochemistry of the surface and groundwater (e.g., Carol et al., 2009, Carol et al., 2011, Carol et al., 2012, Carol and Kruse, 2012) and the present and expected hydro-morphologic setting in relation to relative sea level rise (Tosi et al., 2013). To date, no studies have integrated the previous natural surface and subsurface hydrology and analyzed the effect of human interventions at both regional and local scales. The retrospective assessment of hydrologic conditions is a methodology that conceptualizes the surficial water and groundwater interactions that are driven by natural conditions and human-induced processes. The results of studies of site-specific processes can successfully be extended to a larger scale to characterize the hydrological setting of the entire coastland. The retrospective assessment of hydrologic conditions requires the identification, compilation and analysis of relevant existing data sets. Remotely sensed data provide a synoptic view of the terrestrial landscape and can be especially useful for assessing and monitoring natural resources (e.g., surface water, vegetation, wetlands) over large areas with frequent regular observations (Jiang et al., 2008, Jiang et al., 2013, Sleeter et al., 2013). Satellite images represent a unique means of evaluating long-term changes in climate and hydrology over wide and inaccessible areas that lack in situ measurements. Images provide support to regional hydrological studies because they reveal patterns, land cover and land use modifications (Campbell, 1996). Moreover, they can provide reliable information about the extent and spatial distribution of “hot spot” events (i.e., floods due to rivers, storm surges or intense rainfall). The systematic archiving of Landsat data makes this information valuable for retrospective analyses of environmental characteristics that are applicable to regional studies (Wulder et al., 2012).

The overall aim of this work is to develop a conceptual model of the hydrologic setting of the Samborombón coastland under natural conditions, such as those at the beginning of the last century, and modified by anthropogenic interventions. The model was developed by a retrospective assessment of the hydrological conditions that was aided by the interpretation of satellite images that were integrated with the results of previous studies and observations from exploratory field investigations.

Section snippets

Study site description

The coastland of Samborombón Bay (Fig. 1) is part of the Río de la Plata estuary and is influenced by the estuary's semidiurnal microtidal regime (Acha et al., 2008). The tidal wedge penetrates from the Atlantic Ocean into the upstream portion of the estuary with salinities that vary from 20 to 1 g/L at the outer and upper limits, respectively (Guerrero et al., 1997).

The climate is humid temperate with an average annual rainfall of 940 mm and evapotranspiration rates reach 770 mm/yr (Pousa et al.,

Results

The retrospective analysis focused on the ecohydrological responses to the human activities at regional and local scales. The main anthropogenic modifications to the hydrological processes are due to (i) channelization, such as the excavation of drainage channels, (ii) mining of the shell ridges, and (iii) construction of embankments, such as dykes, tide embankments and roads.

Discussion and conclusion

Hydrological changes due to channelization, mining and embankments have been reported in many wetlands around the world (Middleton, 1999, Simenstad et al., 2006). Several extensive stream channelization projects have been constructed to control flooding due to heavy rainfall and to reclaim land for agriculture and urbanization. Channelization typically includes deepening and widening the river beds and straightening the river by cutting off meanders. It increases both the surficial flow and

Acknowledgements

This work was performed under the Scientific Cooperation Agreement between CONICET (Argentina) and CNR (Italy), Program 2013–2014, Project “Fresh–salt-waters in high-value coastlands: from the hydro-geophysical/geochemical characterization of the present interactions to the modeling quantification of the expected effects of climate changes”. The satellite images were obtained from the U.S. Geological Survey – Earth Resources Observation and Science (EROS) Center. The constructive comments of

References (76)

  • D. Jiang et al.

    Vegetation dynamics and their response to freshwater inflow and climate variables in the Yellow River Delta, China

    Quatern. Int.

    (2013)
  • C.A. Magalhães et al.

    PCBs, PBDEs and organochlorine pesticides in crabs Hepatus pudibundus and Callinectes danae from Santos bay, state of Sao Paulo, Brazil

    Mar. Pollut. Bull.

    (2012)
  • W. Mitsch

    What is ecological engineering?

    Ecol. Eng.

    (2012)
  • W. Ren et al.

    Urbanization, land use, and water quality in Shanghai: 1947–1996

    Environ. Int.

    (2003)
  • C. Robinson et al.

    Effect of tidal forcing on a subterranean estuary

    Adv. Water Resour.

    (2007)
  • C. Simenstad et al.

    When is restoration not? Incorporating landscape-scale processes to restore self-sustaining ecosystems in coastal wetland restoration

    Ecol. Eng.

    (2006)
  • C.G. Simionato et al.

    A numerical study of the barotropic circulation of the Rio de la Plata estuary: sensitivity to bathymetry, earth rotation and low frequency wind variability

    Estuarine Coastal Shelf Sci.

    (2004)
  • B.M. Sleeter et al.

    Land-cover change in the conterminous United States from 1973 to 2000

    Global Environ. Change

    (2013)
  • Y. Tang et al.

    Response of soil microbial respiration of tidal wetlands in the Yangtze River Estuary to different artificial disturbances

    Ecol. Eng.

    (2011)
  • J.M. Teal et al.

    Ecological engineering, design, and construction considerations for marsh restorations in Delaware Bay, USA

    Ecol. Eng.

    (2002)
  • P. Teatini et al.

    Understanding the hydrogeology of the Venice Lagoon subsurface with airborne electromagnetic

    J. Hydrol.

    (2011)
  • L.L. Weishar et al.

    Designing large-scale wetland restoration for Delaware Bay

    Ecol. Eng.

    (2005)
  • A.D. Werner et al.

    Tidal impacts on riparian salinities near estuaries

    J. Hydrol.

    (2006)
  • A.D. Werner et al.

    Seawater intrusion processes, investigation and management: recent advances and future challenges

    Adv. Water Resour.

    (2013)
  • M.A. Wulder et al.

    Opening the archive: how free data has enabled the science and monitoring promise of Landsat

    Remote Sens. Environ.

    (2012)
  • M. Acha et al.

    An overview of physical and ecological processes in the Río de la Plata Estuary

    Cont. Shelf Res.

    (2008)
  • F. Ameghino

    Las secas y las inundaciones en la Provincia de Buenos Aires. Obras de retencion y no de desague

    (1884)
  • F. Braga et al.

    Salt contamination process in coastal aquifers of Yantai, China, and Venice, Italy

  • F. Braga et al.

    EPHESUS: remote sensing for coastal processes in southern Bohai Sea, China

  • A. Brookes

    Channelized Rivers: Perspectives for Environmental Management

    (1988)
  • L. Carbognin et al.

    Interaction between climate changes, eustasy and land subsidence in the North Adriatic Region, Italy

    Marine Ecol.

    (2002)
  • L. Carbognin et al.

    The impact of relative sea level rise on the northern Adriatic Sea coast, Italy

    WIT Trans. Ecol. Environ.

    (2009)
  • E. Carol et al.

    Surface water and groundwater response to the tide in coastal wetlands: assessment of a marsh in the outer Río de la Plata estuary, Argentina

    J. Coastal Res.

    (2013)
  • S.M. Cheong et al.

    Coastal adaptation with ecological engineering

    Nat. Clim. Change

    (2013)
  • V.H. Conzonno et al.

    The impact of man made hydrology on the lower stream bed of the Salado River drainage basin (Argentina)

    Environ. Geol.

    (2001)
  • C. Dapeña et al.

    Composición isotópica de la lluvia de Buenos Aires. Su importancia para el estudio de los sistemas hidrológicos pampeanos

    Rev. Latino Am. Hidrogeol.

    (2004)
  • J.W. Day et al.

    Sustainability and place: how emerging mega-trends of the 21st century will affect humans and nature at the landscape level

    Ecol. Eng.

    (2013)
  • Cited by (27)

    • Past and present conservation of south American estuaries

      2023, Estuarine, Coastal and Shelf Science
    • Evaluation of SAR C-band interferometric coherence time-series for coastal wetland hydropattern mapping

      2021, Journal of South American Earth Sciences
      Citation Excerpt :

      Samborombón Bay is an extensive intertidal wetland, located on the Argentinean side of the outer estuary of the Rio de la Plata, between Punta Piedras and Punta Rasa (Buenos Aires Province, Argentina). This wetland area constitutes a typical low-lying coastal system, covering 3000 km2, around 1 m above the mean sea level, with a shoreline extending approximately 180 km (Carol et al., 2014). Samborombón Bay is the largest and most important wetland on the temperate South Atlantic coast, being declared a Ramsar Site in 1997, with highly valued habitat for many trans-hemispheric migratory bird species and a remnant population of the endangered Pampas deer (Ozotoceros bezoarticus celer) (Vila et al., 2008), which have forward the creation of several protected areas, including Campos del Tuyú National Park (Tosi et al., 2013).

    • Hydro-environmental changes assessment after Guadalhorce River mouth channelization. An example of hydromodification in southern Spain

      2020, Catena
      Citation Excerpt :

      However, these engineering solutions usually have an important hydrological impact (Watson et al., 1999), causing changes in water velocity and sediment transport capacity (Brookes, 1988). They also have hydrogeological effects, such as modifications in the groundwater discharge into streams (LaSage et al., 2008), marine intrusion (Petalas, 2013), tidal flooding and seawater encroachment (Carol et al., 2014). Regarding surface water/groundwater exchange, Constantz et al. (2016) demonstrated alterations in the biogeochemical processing and in the ecological systems.

    • Shoreline change rates along Samborombón Bay, Río de la Plata estuary, Argentina

      2020, Estuarine, Coastal and Shelf Science
      Citation Excerpt :

      a). The marshlands are approximately 100 m wide at the northern tip of the bay, more than 20 km wide at the southern, they have an average height of 1.5 m above mean sea level, and are composed of low permeability silty-clay sediments (Carol et al., 2014). Marsh vegetation exhibits a strong zonation across the elevation gradient, through their tolerance to flooding and salinity (Isacch et al., 2006).

    View all citing articles on Scopus
    View full text