Morphological, hydrological, biogeochemical and ecological changes and challenges in river restoration – the Thur River case study

River restoration can enhance river dynamics, environmental heterogeneity and biodiversity, but the underlying processes governing the dynamic changes need to be understood to ensure that restoration projects meet their goals, and adverse effects are prevented. In particular, we need to comprehend how hydromorphological variability quantitatively relates to ecosystem functioning and services, biodiversity as well as ground- and surface water quality in restored river corridors. This involves (i) physical processes and structural properties, determining erosion and sedimentation, as well as solute and heat transport behavior in surface water and within the subsurface; (ii) biogeochemical processes and characteristics, including the turnover of nutrients and natural water constituents; and (iii) ecological processes and indicators related to biodiversity and ecological functioning. All these aspects are interlinked, requiring an interdisciplinary investigation approach. Here, we present an overview of the recently completed RECORD (REstored CORridor Dynamics) project in which we combined physical, chemical, and biological observations with modeling at a restored river corridor of the perialpine Thur River in Switzerland. Our results show that river restoration, beyond inducing morphologic changes that reshape the river bed and banks, triggered complex spatial patterns of bank infiltration, and affected habitat type, biotic communities and biogeochemical processes. We adopted an interdisciplinary approach of monitoring the continuing changes due to restoration measures to address the following questions: How stable is the morphological variability established by restoration? Does morphological variability guarantee an improvement in biodiversity? How does morphological variability affect biogeochemical transformations in the river corridor? What are some potential adverse effects of river restoration? How is river restoration influenced by catchment-scale hydraulics and which feedbacks exist on the large scale? Beyond summarizing the major results of individual studies within the project, we show that these overarching questions could only be addressed in an interdisciplinary framework.

[1]  T. Günther,et al.  A filtering method to correct time-lapse 3D ERT data and improve imaging of natural aquifer dynamics , 2012 .

[2]  Luca Ridolfi,et al.  POLITECNICO DI TORINO Repository ISTITUZIONALE Modeling the interactions between river morphodynamics and riparian vegetation / , 2022 .

[3]  S. Greenhalgh,et al.  Zonation for 3D aquifer characterization based on joint inversions of multimethod crosshole geophysical data , 2010 .

[4]  E. Samaritani.  Spatio-temporal variability and restoration effects on below-ground biodiversity and soil ecosystem functioning at the Thur floodplain, Switzerland , 2013 .

[5]  J. Hering,et al.  NOM degradation during river infiltration: effects of the climate variables temperature and discharge. , 2013, Water research.

[6]  W. McDowell,et al.  Twelve testable hypotheses on the geobiology of weathering , 2011, Geobiology.

[7]  R. Brauchler,et al.  Structure-coupled joint inversion of geophysical and hydrological data , 2013, 1701.01360.

[8]  J. Hollender,et al.  Degradation of polar organic micropollutants during riverbank filtration: complementary results from spatiotemporal sampling and push-pull tests. , 2013, Environmental science & technology.

[9]  M. Schirmer,et al.  Thirty years of river restoration in Switzerland: implemented measures and lessons learned , 2014, Environmental Earth Sciences.

[10]  P. Molnar,et al.  Biomass selection by floods and related timescales: Part 1. Experimental observations , 2012 .

[11]  Bruno Merz,et al.  At what scales do climate variability and land cover change impact on flooding and low flows? , 2007 .

[12]  D. Baldwin,et al.  The effects of short‐term inundation on carbon dynamics, microbial community structure and microbial activity in floodplain soil , 2011 .

[13]  P. Burlando,et al.  Above‐ground and below‐ground Salix dynamics in response to river processes , 2014 .

[14]  Emily H. Stanley,et al.  THE FUNCTIONAL SIGNIFICANCE OF THE HYPORHEIC ZONE IN STREAMS AND RIVERS , 1998 .

[15]  Martin W. Doyle,et al.  In‐stream geomorphic structures as drivers of hyporheic exchange , 2008 .

[16]  S. Fisher,et al.  The influence of a riparian shrub on nitrogen cycling in a Sonoran Desert stream , 2001 .

[17]  Other.  Directive 2000/60/EC of the European Parliament and of The Council of 23 October 2000 establishing a Framework for Community Action in the Field of Water Policy (Water Framework Directive) , 2000 .

[18]  M. Palmer,et al.  Hydroecology and river restoration: Ripe for research and synthesis , 2006 .

[19]  Johan Alexander Huisman,et al.  Assessing the impact of land use change on hydrology by ensemble modeling (LUCHEM) , 2009 .

[20]  T. Günther,et al.  Constraining 3-D electrical resistance tomography with GPR reflection data for improved aquifer characterization , 2012 .

[21]  Mary Lynn Baeck,et al.  Field studies of the storm event hydrologic response in an urbanizing watershed , 2005 .

[22]  Niklas Linde,et al.  3-D characterization of high-permeability zones in a gravel aquifer using 2-D crosshole GPR full-waveform inversion and waveguide detection , 2013 .

[23]  S. Bernasconi,et al.  Nitrate leaching from short-hydroperiod floodplain soils , 2012 .

[24]  J. Stromberg,et al.  Importance of low-flow and high-flow characteristics to restoration of riparian vegetation along rivers in arid south-western United States , 2007 .

[25]  Niklas Linde,et al.  Imaging and quantifying salt-tracer transport in a riparian groundwater system by means of 3D ERT monitoring , 2012 .

[26]  Tobias Vogt,et al.  Estimation of seepage rates in a losing stream by means of fiber-optic high-resolution vertical temperature profiling , 2010 .

[27]  Andrew J. Boulton,et al.  Hyporheic rehabilitation in rivers: restoring vertical connectivity , 2007 .

[28]  B. Arheimer,et al.  Regional and global concerns over wetlands and water quality. , 2006, Trends in ecology & evolution.

[29]  Gilles Pinay,et al.  Stream regulation and nitrogen dynamics in sediment interstices: comparison of natural and straightened sectors of a third‐order stream , 2004 .

[30]  P. Burlando,et al.  Mechanisms of vegetation uprooting by flow in alluvial non-cohesive sediment , 2011 .

[31]  Jill R. Welter,et al.  Flowpaths as Integrators of Heterogeneity in Streams and Landscapes , 2005 .

[32]  J. Meyer,et al.  Standards for ecologically successful river restoration , 2005 .

[33]  Sharon Woolsey,et al.  A strategy to assess river restoration success , 2007 .

[34]  Niklas Linde,et al.  The borehole-fluid effect in electrical resistivity imaging , 2010 .

[35]  E. Mitchell,et al.  Toward the use of testate amoeba functional traits as indicator of floodplain restoration success , 2012 .

[36]  S. Wondzell,et al.  Geomorphic controls on hyporheic exchange flow in mountain streams , 2003 .

[37]  R. Naiman,et al.  FOREST‐RIVER INTERACTIONS: INFLUENCE ON HYPORHEIC DISSOLVED ORGANIC CARBON CONCENTRATIONS IN A FLOODPLAIN TERRACE 1 , 2002 .

[38]  Niklas Linde,et al.  Estimating traveltimes and groundwater flow patterns using 3D time-lapse crosshole ERT imaging of electrical resistivity fluctuations induced by infiltrating river water , 2012 .

[39]  E. Mitchell,et al.  Patterns of earthworm communities and species traits in relation to the perturbation gradient of a restored floodplain , 2012 .

[40]  Andreas Wombacher,et al.  Hydrodynamic model calibration from pattern recognition of non-orthorectified terrestrial photographs , 2014, Comput. Geosci..

[41]  D. Wardle,et al.  Ecological Linkages Between Aboveground and Belowground Biota , 2004, Science.

[42]  P. Burlando,et al.  Effects of streamflow variability on the vertical root density distribution of willow cutting experiments , 2012 .

[43]  M. Schirmer,et al.  Modeling the dynamics of oxygen consumption upon riverbank filtration by a stochastic–convective approach , 2013 .

[44]  B. Wehrli,et al.  Intensified organic carbon dynamics in the ground water of a restored riparian zone , 2012 .

[45]  K. Tockner,et al.  Flood pulses control soil nitrogen cycling in a dynamic river floodplain , 2014 .

[46]  L. Ridolfi,et al.  Modelling river and riparian vegetation interactions and related importance for sustainable ecosystem management , 2009, Aquatic Sciences.

[47]  M. Palmer,et al.  River restoration, habitat heterogeneity and biodiversity: a failure of theory or practice? , 2010 .

[48]  K. Tockner,et al.  Heterogeneity of soil carbon pools and fluxes in a channelized and a restored floodplain section (Thur River, Switzerland) , 2011 .

[49]  A. Gurnell.  Plants as river system engineers , 2014 .

[50]  Larry MacDonnell,et al.  River restoration , 2005 .

[51]  K. Tockner,et al.  Soil nitrogen dynamics in a river floodplain mosaic. , 2012, Journal of environmental quality.

[52]  Andreas Wombacher,et al.  Modern comprehensive approach to monitor the morphodynamic evolution of restored river corridors , 2010 .

[53]  P. Renard,et al.  Assessing the effect of different river water level interpolation schemes on modeled groundwater residence times , 2014 .

[54]  P. Schneider,et al.  Integrating river cross section measurements with digital terrain models for improved flow modelling applications , 2010, Comput. Geosci..

[55]  Meta-Analysis Services by Ecological Restoration : A Enhancement of Biodiversity and Ecosystem , 2009 .

[56]  A. Binley,et al.  Laboratory Title Imaging and quantifying salt-tracer transport in a riparian groundwater system by means of 3 D ERT monitoring Permalink , 2012 .

[57]  M. Delong,et al.  The riverine ecosystem synthesis: biocomplexity in river networks across space and time , 2006 .

[58]  B. Wehrli,et al.  Nitrate removal in a restored riparian groundwater system: functioning and importance of individual riparian zones , 2012 .

[59]  D. A. Barry,et al.  Analysis of carbon and nitrogen dynamics in riparian soils: model development. , 2012, The Science of the total environment.

[60]  M. Palmer,et al.  River restoration: OPINION , 2005 .

[61]  N. Linde,et al.  Towards improved instrumentation for assessing river-groundwater interactions in a restored river corridor , 2011 .

[62]  Mario Schirmer,et al.  Fluctuations of electrical conductivity as a natural tracer for bank filtration in a losing stream , 2010 .

[63]  D. A. Barry,et al.  Analysis of carbon and nitrogen dynamics in riparian soils: model validation and sensitivity to environmental controls. , 2012, The Science of the total environment.

[64]  Peter Molnar,et al.  An observation‐based stochastic model for sediment and vegetation dynamics in the floodplain of an Alpine braided river , 2009 .

[65]  C. Kremen.  Managing ecosystem services: what do we need to know about their ecology? , 2005, Ecology letters.

[66]  P Goodwin,et al.  Ecology. Synthesizing U.S. river restoration efforts. , 2005, Science.

[67]  L. Ridolfi,et al.  Significance of the riparian vegetation dynamics on meandering river morphodynamics , 2007 .

[68]  K. Tockner,et al.  River and Wetland Restoration: Lessons from Japan , 2006 .

[69]  P. Perona,et al.  Biomass selection by floods and related timescales. Part 2: Stochastic modeling , 2012 .

[70]  Niklas Linde,et al.  3D crosshole ERT for aquifer characterization and monitoring of infiltrating river water , 2011 .

[71]  P. Renard,et al.  New Methods to Estimate 2D Water Level Distributions of Dynamic Rivers , 2013, Ground water.

[72]  Mary Lynn Baeck,et al.  Variation in the instream dissolved inorganic nitrogen response between and within rainstorm events in an urban watershed , 2008, Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering.

[73]  Niklas Linde,et al.  Self-potential investigations of a gravel bar in a restored river corridor , 2010 .

[74]  S. Darby,et al.  Bank and near-bank processes in an incised channel , 2000 .

[75]  Mario Schirmer,et al.  Micropollutant loads in the urban water cycle. , 2010, Environmental science & technology.

[76]  S. Bernasconi,et al.  A new isolation procedure of nitrate from freshwater for nitrogen and oxygen isotope analysis. , 2011, Rapid communications in mass spectrometry : RCM.

[77]  Bruce Abernethy,et al.  The distribution and strength of riparian tree roots in relation to riverbank reinforcement , 2001 .

[78]  Jean Poesen,et al.  Impact of plant roots on the resistance of soils to erosion by water: a review , 2005 .

[79]  H. Pereira,et al.  Towards the global monitoring of biodiversity change. , 2006, Trends in ecology & evolution.

[80]  Paolo Perona,et al.  Impact of floods on the statistical distribution of riverbed vegetation , 2013 .

[81]  T. Addiscott,et al.  When does nitrate become a risk for humans? , 2008, Journal of environmental quality.