Current status and restoration options for floodplains along the Danube River

https://doi.org/10.1016/j.scitotenv.2015.09.073Get rights and content

Highlights

  • Floodplain areas in large river systems have decreased immensely during the last century.

  • The potential Danube floodplain area useful for restoration remains high (8102 km2)

  • Restoration is limited by stakeholder needs, acceptance, and resource availability.

  • Combining different EU targets can increase the effectiveness of restoration projects.

Abstract

Floodplains are key ecosystems of riverine landscapes and provide a multitude of ecosystem services. In most of the large river systems worldwide, a tremendous reduction of floodplain area has occurred in the last 100 years and this loss continues due to pressures such as land use change, river regulation, and dam construction. In the Danube River Basin, the extent of floodplains has been reduced by 68% compared to their pre-regulation area, with the highest losses occurring in the Upper Danube and the lowest in the Danube Delta. In this paper, we illustrate the restoration potential of floodplains along the Danube and its major tributaries. Via two case studies in the Upper and Lower Danube, we demonstrate the effects of restoration measures on the river ecosystem, addressing different drivers, pressures, and opportunities in these regions. The potential area for floodplain restoration based on land use and hydromorphological characteristics amounts to 8102 km2 for the whole Danube River, of which estimated 75% have a high restoration potential. A comparison of floodplain status and options for restoration in the Upper and Lower Danube shows clear differences in drivers and pressures, but certain common options apply in both sections if the local context of stakeholders and societal needs are considered. New approaches to flood protection using natural water retention measures offer increased opportunities for floodplain restoration, but conflicting societal needs and legal frameworks may restrict implementation. Emerging issues such as climate change and invasive non-native species will need careful consideration in future restoration planning to minimize unintended effects and to increase the resilience of floodplains to these and other pressures.

Introduction

Floodplains are crucial components of riverine landscapes (Tockner and Stanford, 2002). They are important areas for biodiversity and contribute to a broad variety of ecosystem functions by controlling the regional water cycle and the retention and transformation of nutrients in river systems (Weigelhofer et al., 2015, Sanon et al., 2012, Schindler et al., 2014). Their importance in fluvial landscapes is related to the high spatial heterogeneity in concert with a high and flood-driven temporal variability (Tockner et al., 2000). These dynamic fluvial processes are responsible for habitat succession and rejuvenation (Hohensinner and Drescher, 2008), leading to a high biodiversity along aquatic – terrestrial boundaries (Bunn and Arthington, 2002). Lateral hydrological connectivity, defined as the water exchange between floodplain and river, is the key determinant of water-related ecosystem processes such as nutrient turnover, vegetation development, and geomorphic change (Amoros and Bornette, 2002, Hein et al., 2004, Schoenbrunner et al., 2012, Welti et al., 2012).

Although there is a wide appreciation of the ecosystem services provided by floodplains and their vital role in riverine landscapes (e.g. Posthumus et al., 2010, Sanon et al., 2012, Schindler et al., 2014), there have been dramatic losses of floodplain habitat due to land reclamation and channel engineering, resulting in a functional degradation of these systems worldwide (Tockner et al., 2010). The reduction and degradation of floodplain systems has diminished their capacity for water retention, thus enhancing flood risks (Habersack et al., 2015), while other key floodplain functions and services, such as groundwater replenishment, nutrient storage (Hein et al., 2004), and water purification have also declined in effectiveness. The dramatic loss of riparian ecosystems threatens the conservation of key species and habitats, such as pioneer plants and soft- and hardwood tree species of alluvial forests (Scholz et al., 2012) and the aquatic vegetation of backwater systems (Keruzore et al., 2013).

These problems are particularly acute in the case of the Danube. With a length of approximately 2800 km, the Danube crosses 15 countries from its origins in southern Germany to its confluence with the Black Sea (Romania). It drains a catchment of approximately 801,100 km2 linking different natural and cultural landscapes and shaping the history of the region like no other European river (Tockner et al., 2009). Human culture and development have greatly affected the Danube River and the surrounding landscapes. Over the last century, the floodplains of the Danube and its tributaries have been subject to major human interventions causing significant changes in the hydromorphology of the river-floodplain ecosystem (Hohensinner and Drescher, 2008). The increasing demands for land for settlement and agriculture have resulted in large-scale river regulation measures for flood protection, forcing the river into a single, spatially restricted channel between extended dams. About 39% or 1111 river km of the entire Danube are impounded by a total of 78 dams (ICPDR, 2009). As a result, more than 68% of the active floodplains of the Danube River, which are in frequent exchange with the main river channel, have already been lost (e.g. Danube Pollution Reduction Programme (DPRP), 1999, Schwarz, 2010, Tockner et al., 2009). The consequences of these changes are predictable, and include an increase in serious flooding in different regions of the catchment, an increasing pollution load due to continuing emissions and reduced retention capacities, the loss of physical habitat diversity, and a correspondingly high percentage of endangered riverine species (ICPDR, 2009). Taken together, the Danube River Basin is therefore among the most pressurized large river catchments in the world (Tockner et al., 2009).

An improvement of the current status of residual floodplains through the basin-wide application of restoration measures is one of the key water management issues identified in the Danube River Basin Management Plan (DRBMP; ICPDR, 2009). The political changes in Central and Eastern Europe and respective EU policies (EC Water Framework Directive, EC Floods Directive, EC Habitats and Birds Directives; Council of the European Communities, 1992, Council of the European Communities, 2000, Council of the European Communities, 2007) are fostering efforts to protect the remaining Danube floodplains and restore the former hydrological dynamics by re-connecting floodplains with the main river. In addition, the 1975 Ramsar Convention on Wetlands (www.ramsar.org) supports the further conservation and restoration of floodplains and was instrumental in securing early protection for some examples of Danube floodplain wetland.

This paper presents the current status and the development perspectives of floodplains along the Danube River and its major tributaries. Based on the assessment of the overall restoration potential of Danube floodplains, we (i) present case studies from the Upper and Lower Danube to compare different approaches, (ii) assess the potential of various restoration measures to improve floodplain conditions, considering local drivers, obstacles, and opportunities, and (iii) address societal aspects concerned within the Danube River Basin.

Section snippets

Current state and restoration potential of floodplains in the Danube River Basin (DRB)

Assessing the restoration potential of Danube floodplains with respect to their current state and various pressures in the different reaches of the DRB is one of the pre-requisites to support and stimulate restoration projects. The first comprehensive and systematic evaluation of existing floodplains along the Danube and in the lowland parts of its major tributaries was commissioned by the UNDP/GEF as part of the Danube River Pollution Reduction Programme (Danube Pollution Reduction Programme

Austrian Danube floodplains between Vienna and Bratislava

The 45 km river stretch between Vienna and Bratislava is located within one of the last free-flowing sections of the Upper Danube River (Danube Pollution Reduction Programme (DPRP), 1999, Reckendorfer et al., 2005). Large-scale river regulation measures in the 19th century, designed to improve navigation and flood protection, have resulted in the isolation of the once extensive and dynamic floodplains from the main river channel and their degradation to a chain of decoupled floodplain remnants

New approaches in flood protection

River engineering to increase flood protection is one of the main reasons for the dramatic loss of floodplain areas in Europe (Hohensinner and Drescher, 2008). Until the end of the 20th century, flood protection consisted of the construction of dams and levees to retain flood water within the channel and thus prevent flooding of terrestrial surroundings. However, after the severe floods in Europe at the beginning of the millennium (Willi and Eberli, 2006, Barredo, 2007, Habersack et al., 2014),

Conclusion

While the assessment of restoration potential clearly demonstrates the existence of large areas with a high potential for restoration, critical gaps remain in the implementation of restoration projects, highlighting the limitations posed by stakeholder needs, public acceptance, and resource availability. Including these factors alongside assessment at smaller spatial scales might improve the understanding of which factors are crucial for floodplain restoration under different environmental and

Acknowledgments

The DANCERS project received funding from the European Union's Seventh Programme for research, technological development and demonstration under grant agreement no. 603805.

The project GWVLOBAU was funded by the European Agricultural Fund for Rural Development LE 07-13 under the grant agreement 323A/2010/043.

References (86)

  • S. Birk et al.

    Harmonising the bioassessment of large rivers in the absence of near-natural reference conditions — a case study of the Danube River

    Freshw. Biol.

    (2012)
  • S. Bogdanovic

    Legal aspects of transboundary water management in the Danube Basin

    Arch. Hydrobiol. Suppl.

    (2005)
  • C. Bondar

    Studiu sectorial referitor la hidrologie și calitatea apei pentru elaborarea Obiectivelor de management pentru Conservarea Biodiversității și Dezvoltare Durabilă în Rezervația Biosferei Delta Dunării

    (1996)
  • P.J. Boon

    The catchment approach as the scientific basis of river basin management

    Arch. Hydrobiol. Suppl.

    (2005)
  • J. Bloesch

    Flood plain conservation in the Danube River Basin, the link between hydrology and limnology: summary report on the 34th IAD-conference, August 27-30, 2002, in Tulcea (Romania) and the 21st IHP/UNESCO-hydrological conference, September 2-6, 2002, in Bucharest (Romania)

    Arch. Hydrobiol. Suppl.

    (2003)
  • A.D. Buijse et al.

    Restoration strategies for river floodplains along large lowland rivers in Europe

    Freshw. Biol.

    (2002)
  • S.E. Bunn et al.

    Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity

    Environ. Manag.

    (2002)
  • CLC, 2006 (Corine Land Cover inventory) Technical Guidelines, 2007. EEA Technical report, No 17/2007. ISSN...
  • Council of the European Communities

    Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora

    Off. J. Eur. Communities

    (1992)
  • Council of the European Communities

    Council Directive 2000/60/EC of 23 October 2000 establishing a framework for community action in the field of water policy

    Off. J. Eur. Communities

    (2000)
  • Council of the European Communities

    Council directive 2007/60/EC of 23 October 2007 on the assessment and management of flood risks

    Off. J. Eur. Communities

    (2007)
  • A. Covasnianu et al.

    R.E.E.L.D. (Economical and Ecological Reconstruction of the Danube Flood Plain) Campaign: airborne LIDAR data and GIS technique outputs

  • Danube Pollution Reduction Programme (DPRP)

    Evaluation of Wetlands and floodplain areas in the Danube River Basin. WWF Danube-Carpathian Programme and WWF-Auen-Institut (WWF-Germany)

    (1999)
  • European Commission

    Common Implementation Strategy for the Water Framework Directive (2000/60/EC): Guidance document N. 12: the role of wetlands in the Water Framework Directive

    (2003)
  • European Commission

    Green Infrastructure (GI) — enhancing Europe's natural capital

  • D. Gilvear et al.

    Channel dynamics and geomorphic variability as controls on gravel bar vegetation; River Tummel, Scotland

    River Res. Appl.

    (2006)
  • S. Gollasch et al.

    National checklist for aquatic alien species in Germany

    Aquat. Invasions

    (2006)
  • GZÜV — Gewässerzustandsüberwachungsverordnung, 2006. BGBl. II Nr. 479/2006, Novellierung mit BGBl. II Nr. 465/2010....
  • H. Habersack et al.

    Large rivers in the anthropocene: insights and tools for unterstanding climatic, land use and reservoir influences

    Water Resour. Res.

    (2014)
  • H. Habersack et al.

    Floodplain evaluation matrix (FEM): an interdisciplinary method for evaluating river floodplains in the context of integrated flood risk management

    Nat. Hazards

    (2015)
  • S. Hohensinner et al.

    Historical change of European floodplains: the Danube River in Austria

  • ICPDR

    Development of Inland Navigation and Environmental Protection in the Danube River Basin. Vienna

    (2008)
  • ICPDR

    Danube River Basin Management Plan (DRBMP) according to EU Water Framework Directive (WFD). Vienna.

    (2009)
  • ICPDR, 2010. EU PLATINA manual on Good Practices in Sustainable Waterway Planning. PLATINA SWP 5.3 project (2008–2010)....
  • ICPDR

    Climate Adaption Strategy for the Danube River Basin

    (2013)
  • ICPDR

    Transnational monitoring network — Yearbook 2012, 2014, Vienna

    (2014)
  • ICPDR

    Joint Danube Survey 3. A comprehensive analysis of Danube Water Quality. Vienna

    (2015)
  • JRC

    Annual Report of the Joint Research Center of the European Commission 2012 — Environment and Climate Change

    (2012)
  • A. Keruzore et al.

    The role of lateral connectivity in the maintenance of macrophyte diversity and production in large rivers

    Aquat. Conserv. Mar. Freshwat. Ecosyst.

    (2013)
  • G. Kum

    Der einfluss der öffnungsmaßnahmen auf die makrophytengemeinschaft im regelsbrunner altarmsystem — the impact of restoration on the macrophyte community of the “regelsbrunner Au”

    Abh. Zool.-Bot. Ges. Österreich

    (2004)
  • C.M. Lorenz et al.

    Concepts in river ecology: implications for indicator development

    Regul. Rivers Res. Manag.

    (1997)
  • G. Lovász

    Water temperatures of the Danube and Tisza Rivers in Hungary

    Hungarian Geographical Bulletin

    (2012)
  • LUCAS — Land Use/Cover Area Frame Survey, 2012. Technical Reference Document: C-3 Land use and Land Cover...
  • Cited by (0)

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