Wednesday 3rd of july – from 10:30 to 18:30
Session D6 : Connectivity and habitat – 2
Assessing mesoscale habitat availability in relation to discharge in braided river reaches
BAJRAMI Flamur, SOTO PARRA Tulio, PINNA Beatrice, COMBATTI Michele, POLITTI Emilio, FARÒ David, NEGRO Giovanni, TUBINO Marco, VEZZA Paolo, ZOLEZZI Guido
Italy
Short abstract : Habitat modelling in rivers is increasingly being applied in both research and practical contexts for water resources management, nature conservation and river restoration planning and impact assessment. Especially in various water resources management applications, the core of habitat modeling lies in the so called “habitat – discharge rating curve”, which relates the available habitat area for a target biological species / life stage with the flowing discharge in a particular river reach of interest. Such relation is generally obtained through intensive field surveys, which are complemented by the application of 2D hydraulic models and remote / proximal sensing techniques in larger river reaches with complex morphologies.
This study explores habitat modeling in braided river systems, focusing on the Piave River (Italy) and the Sarantaporos River (Albania/Greece). These morphologically dynamic reaches pose unique challenges and opportunities for habitat modelling. A hybrid methodology combining targeted field measurements with hydraulic modeling was applied to overcome the limitations of traditional approaches. High-resolution photogrammetry from drone surveys, supported by ground control points, provided detailed orthophotos and corrected Digital Terrain Models (DTMs). Hydraulic simulations across a range of discharges were conducted using the corrected DTMs, enabling the identification of Hydro morphological Units (HMUs) and the derivation of flow-habitat curves using Sim Stream Web software.
Preliminary results indicate that the habitat-discharge relationship in braided reaches diverges from the single-peak pattern observed in single-channel systems. In braided rivers, increasing discharge initially triggers an alternation between suitable and unsuitable habitat conditions due to the activation of additional channels and redistribution of flow. However, at very high discharges, habitat suitability declines as the channel start to decries due a merging for the hight water level. These findings highlight the intricate interplay between hydrology, channel morphology, and habitat dynamics in braided rivers.
By advancing our understanding of habitat availability across varying flow conditions, this study provides valuable insights for improving the management and conservation of braided river ecosystems.
Influence of network connectivity on benthic and pelagic algal communities in a Danube floodplain system (Austria)
BONDAR-KUNZE Elisabeth, MOSER Marie-Christine, BILOUS Olena, FUNK Andrea, HEIN Thomas
Autriche
Short abstract : This study investigates the influence of network connectivity on the community composition and function of benthic and pelagic algae in the Danube National Park, Austria. By examining both spatial (static and actual network parameters) and environmental parameters, we aim to understand how these factors influence algal distribution and function. Connectivity indices, including harmonic centrality and betweenness centrality, were calculated to assess static and dynamic network parameters. Preliminary results indicate that static network parameters better describe benthic algae in addition to sediment composition and macrophyte cover, while current parameters are more influential for pelagic communities. Our findings highlight the importance of network connectivity in shaping algal communities and underline the need for conservation strategies that maintain or restore network connectivity in floodplain systems. This research contributes to a deeper understanding of the ecological dynamics within riverine landscapes and informs effective management practices.
Restoring Lateral Connectivity to a large floodplain river on the coastal plain of North America
KONDOLF G Mathias
United-States
Short abstract : With increasing recognition of the importance of restoring lateral connectivity to floodplain water bodies, the Apalachicola river, Florida USA, is notable for its morphologically intact floodplain and floodplain forest, and the unusual nature of the hydrological disconnection of its sloughs (secondary channels) from the mainstem due to sand deposits relict from a failed navigation project in the 20th century. We have undertaken 3 pilot projects to determine the benefits of targeted sand removal from these sloughs. Because the nature of the impairment is so different, these restoration measures are quite different from secondary channel restoration measures described elsewhere.
A new IT tool to identify and classify non-perennial rivers
VEZZA Paolo, BRICHETTO Isabelle, CAVALLO Carmela, DOLIANIDI Christina, GONZÁLEZ COSTAS Almudena, KARAKOSTAS Anastasios, NIKOLAIDIS Nikos, LILLI Maria, MANFREDA Giammarco, NEGRO Giovanni, PALAU-SALVADOR Guillermo, PAPA Maria Nicolina, SANCHIS-IBOR Carles, TSALAGEORGOS Spiros
Italy
Short abstract : Quantifying the intensity of flow intermittency and the spatial and temporal extension of dry riverbeds remains one of the most important gap in non-perennial rivers (NPRs) conservation and management. In this context, satellite images and remote sensing data can be used to identify and classify flow intermittency, detecting flow occurrence along river reaches. Satellite data have a short revisit time (about one week), and the recent availability of free of charge, high spatial resolution data (e.g., ESA Sentinel-2 mission) has already opened up the possibility of innovative applications for NPRs. Based on the results of the RIVERTEMP Erasmus+ project, we present a new web platform that analyses Sentinel-2 multispectral images. The false color composition of the bands SWIR, NIR and RED is automatically generated by the platform. False color images can be used to clearly distinguish water presence and identify the hydrological conditions of river reaches, that can be: “flowing” (F), “ponding” (P) or “dry” (D) conditions. The web tool generates time series of hydrological conditions, allowing the automatic classification of the NPRs based on the frequency and duration of F, P and D classes. A user manual and training materials for university students are also freely available on the website of the project.
Characterization of aquatic refuges to support the resilience of freshwater ecosystems in a global changing context
LUCCHINI Matthieu, STAENTZEL Cybill, TRUTIN Loïc, CHANEZ Etienne, BEISEL Jean-Nicolas
France
Short abstract : Aquatic refuges play a key role in the resilience of freshwater ecosystems facing pressures from climate change and human activities. However, their identification and characterization remain limited due to the lack of consensus on their definition and the absence of diagnostic tools. To address these gaps, we conducted a systematic review of the literature using a recognized framework, the PECO strategy. This first phase allowed us to (i) assess the importance of aquatic refuges for the resilience of lotic ecosystems to disturbances, and (ii) identify the structural, physical, spatial, and biological parameters that define a refuges. Building on this conceptual foundation, these parameters were evaluated under real-world conditions across the Wieslauter basin as part of the Interreg RiverDiv project. This evaluation relied on a multidisciplinary approach combining macroinvertebrate sampling, detailed mapping of river mosaics, and the use of drones for visible and thermal imaging. This integrative approach provides concrete opportunities to enhance the adaptive and sustainable management of aquatic refuges, particularly in a context where their vulnerability to growing pressures raises critical concerns.
Mesohabitat suitability criteria for the spawning of Twaite shad (Alosa fallax, Lacépède 1803)
NEGRO Giovanni, LESA Davide, BERTOLI Marco, GUGLIELMETTO Alessandro, PINNA Beatrice, FORTE Simone, SPADAVECCHIA Claudio, MASCHIO Paolo, PIZZUL Elisabetta, VEZZA Paolo
Italy
Short abstract : Twaite shad (Alosa fallax, Lacépède 1803) is an anadromous fish that relies on European rivers for spawning. However, populations are declining due to river damming and hydro-morphological alterations, which reduce and degrade suitable spawning grounds. This study presents the first meso-scale habitat suitability criteria (HSC) in the literature for the spawning period of A. fallax. Using the MesoHABitat SImulation Model (MesoHABSIM) approach, we identified the geomorphic units (GUs) and associated habitat attributes preferred for mating purpose by A. fallax in the Tagliamento River (NE Italy). Habitat characterization was conducted using Uncrewed Aerial Systems (UAS), a two-dimensional (2D) hydrodynamic model, and field surveys performed during a monitoring period of 15 months. A classification Random Forest (RF) model, with high accuracy (98.8%) and true skill statistic (97.6%), was employed to identify key meso-habitat features for the reproduction of A. fallax. The developed HSC revealed that A. fallax prefers glides and riffles to spawn, with shallow depths (0.15-0.45 m), moderate velocities (0.30-0.75 m/s), and small sediment sizes (0.2-6 cm). Additionally, we employed a non-intrusive monitoring method using infrared cameras, which successfully recorded 72 surface mating events over two nights. This method proved effective since it was possible to precisely define the location, the duration of each mating event and the number of fish involved. The findings provide valuable insights for developing management strategies aimed at preserving or restoring A. fallax spawning habitats.
Designing Specific Habitats as a Measure to Reduce the Impacts on River
HRIBAR Andraž
Slovenia
Short abstract : According to some data, 95% of rivers in Western Europe are more or less degraded. Restoring rivers and re-establishing river ecosystems will therefore be a long but necessary process. In doing so, we must ask ourselves: what are we protecting, or what are we creating? Are the protected geomorphological forms and habitats something created by nature, or something created by humans that nature has taken over? When managing modern rivers, can we draw a clear line between what nature has created and what has been influenced by humans?
We faced such dilemmas when integrating the Brežice Hydroelectric Power Plant into the environment, as we were protecting natural values that were actualy created by humans in the past. Changes in the river regime and climate change, which have altered today’s water needs, posed threats to these values. The way to protect and respond to these changes was to create specific habitats, designed as protected areas for specific organisms.
A multidisciplinary approach was essential in designing these solutions, but it wasn’t enough – a broad perspective was also required. By looking into the past, we could design a future in which nature and humans coexist and share the river.
Occupation of the channels of a braided river by the Odonata
PONT Bernard
France
Short abstract : Eygues river is a 114 kilometre tributary of the Rhône taking its source at about 1100 m above sea level draining the Baronnies massif (Drôme, Hautes Alpes, Vaucluse). Six reaches 2 to 4 km long with active braiding in the middle of the 20th century spread over the entire basin were selected. On each reache, the odonate stand is inventoried by a standardized protocol and two geomorphological parameters are characterized : the evolution of a active channel width between 1960 and 2021 and the diversity of the channel system.
The richness of the dragonfly population in the different reache varies between 6 and 31 species, the total richness of all sections combined reaches 37 species. The correlation between the richness of the odonate population and the diversity of the channel network is strong while it is low with the retraction rate of the active channel width. The main and secondary channels are poor and host species adapted to the fast current. The alluvial and phreatic channels and ponds are home to most of the wealth and each of these types constitutes the optimum habitat for different species.
Session D7 : Riparian environments. To revegetate or not to revegetate? That’s the question
Assessment of Riparian Ecosystems for Sustainable Management in the Face of Climate Change: A Practical and Interdisciplinary Approach
DOPIERALA Romain, FORET Arnaud, JOËT Océane, VERNAY Antoine, MOATAR Florentina, VALETTE Laurent, MAZAGOL Pierre-Olivier
France
Short abstract : Riparian ecosystems are vital for maintaining ecological balance, regulating water quality, and supporting biodiversity. However, these ecosystems are increasingly vulnerable due to climate change and anthropogenic pressures, which intensify water stress, alter hydrological regimes, and heighten the need for effective restoration and renaturation efforts. In response to these challenges, the SAGE Loire in the Rhône-Alpes region has advocated for interdisciplinary approaches to mitigate these threats and promote sustainable management. This project aims to assess the health and functionality of riparian vegetation, integrating spatial, ecological, and hydrological perspectives to inform restoration and management strategies in the face of climate change. By combining geomatics, ecology, and hydrology, the project will create a comprehensive interdisciplinary database and develop an index to characterize riparian vegetation. This index will incorporate GIS-based spatial mapping, ecological indicators of vegetation water stress, and hydrological data on water temperature, providing a holistic tool for effective riparian ecosystem management and restoration.
Byte and rates: multiple combinations of different remote sensing data for biogeomorphic interaction of river system
RUSNÁK Miloš, GOGA Tomáš, AFZALI Hamid, OPRAVIL Šimon, MICHALEJE Lukáš, MD Ashraf
Slovakia
Short abstract : River channels play a crucial role in maintaining landscapes by transferring energy, matter, and nutrients. Nowadays, modern fluvial geomorphology emphasizes the integration and complex understanding of the mutual relationship between river processes and floodplain ecology with an emphasis on riparian vegetation. For this study, the braided-wandering river system of the Belá River was selected for assessment. This river system is a rare and valuable wetland ecosystem affected by morphological degradation and incision. A combination of old historical aerial images (1949-2018) with 50 centimetres accuracy and modern low-resolution (10 meters) satellite data (from 2016) was used for the evaluation and monitoring of biogeomorphological interaction. For extraction of environmental variables (height above the channel, morphometry, vegetation cover), the study used surface and terrain elevation models derived from lidar data. The spatial extent of vegetation was automatically classified from historical black-and-white aerial imagery (1949-1992), RGB orthophotos (2002-2006) and RGB+NIR orthophotos (2009-2018). Monitoring and response to geomorphic adjustment were analysed based on vegetation and moisture indices were calculated from Sentinel-2 satellite data. The spatial distribution of vegetation and moisture indices was found to be independent of the distance from the channel, with notable differences observed across different channel platforms. Seasonal variations in vegetation and moisture indices followed the local hydrological conditions and the annual phenology curve.
Mapping riparian vegetation functional units using multi-source remote sensing data: a case study on alluvial bars
EBENGO Dav, VAUTIER Franck, TABACCHI Eric, WALCKER Romain, ROUSSEL Erwan, COURCOUL Camille, TOUMAZET Jean-Pierre, STEIGER Johannes, BONNIS Anne, ARRIGNON Florent, GONZÁLEZ-SARGAS Eduardo, GARÓFANO-GÓMEZ Virginia, HENRY Annie, MARTÍNEZ-CAPEL Francisco, OTTO Thierry, LUCE Frédéric, TILL-BOTTRAUD Irène, VOLDOIRE Olivier, CORENBLIT Dov
France
Short abstract : One of the objectives of the European Water Framework Directive is to assess the ecological status of water bodies and identify the causes of degradation so that management policies can be adapted and restoration tools implemented. The aim of this study is to characterize and map the functional units of riparian vegetation using very high-resolution remote sensing data that combine multispectral images and LiDAR data. These data were acquired on-site by unmanned laser vehicle over two alluvial bars of the Allier River. The data were cross-referenced with twelve functional vegetation units identified based on the functional traits of plant communities. To distinguish the functional units, three classification algorithms were tested: Random Forest, Gradient Boosting Classifier, and Linear Discriminant Analysis. The Random Forest classification algorithm demonstrated the best performance for classifying functional units on the two studied bars, with average overall accuracies of 93% and 95%. Among the explanatory variables, the digital surface model, canopy height, and digital terrain model proved to be the most significant predictors for discriminating the functional units. These results show that remote sensing data can effectively characterize functional units in riverine ecosystems. Such approaches can be leveraged for large-scale monitoring of conservation status and management of riparian environments.
Unlocking vegetation age estimation and the identification of biogeomorphic floods in a braided river
CRIVELLARO Marta, BELLETTI Barbara, ZOLEZZI Guido, PIEGAY Herve, BERTOLDI Walter
Italy
Short abstract : This study investigates the integration of remote sensing (RS) and cloud computing (CC) to estimate vegetation age and to gain insights on biogeomorphic floods in braided rivers, using the Tagliamento River, Italy, as a case study. A novel algorithm, implemented using Landsat Surface Reflectance and Sentinel-2 products on Google Earth Engine, reconstructs vegetation age dynamics at the pixel scale. Validation with field data and high-resolution imagery highlights spatial overestimations (15%) and temporal underestimations (7 years) due to RS limitations. The analysis of historical flood data reveals the role of low-recurrence interval floods in vegetation turnover and recruitment. Results provide insights into riparian vegetation dynamics and their interactions with hydrogeomorphic processes, underscoring the utility of RS in advancing riverine ecosystem studies.
Machine Learning for Long-Term Riparian Vegetation Monitoring Using Historical Aerial Imagery
Auteurs : AFZALI Hamid, RUSNÁK Miloš
Slovakia
Short abstract : The study evaluates a machine learning-based method for detecting spatial-temporal patterns in braided-wandering multichannel systems using historical aerial imagery, focusing on riparian vegetation.
Towards a panel of indicators for monitoring the alluvial wetlands of the Garonne river
QUINTIN Pauline, LE MÉTAYER Nolwenn, DAMIEN Alexianne, OLICARD Ludovic
France
Short abstract : As part of the multi-site management plan for alluvial wetlands led by the Nature En Occitanie association, one of the targeted actions is to develop a panel of monitoring indicators. The aim of this panel is to harmonise monitoring across the Garonne river and to propose reliable indicators that are easy to monitor over the long term and at an appropriate cost. The indicators allow to assess conservation management measures and the conservation status of key habitats. A bibliography of existing indicators applicable to the alluvial context served as a methodological basis. The monitoring objectives were then chosen according to the ecological and hydromorphological issues raised in the site diagnostics. This panel is currently made up of 14 indicators that meet 3 major monitoring objectives : to assess the state of conservation of alluvial forests ; to assess changes in the state of conservation of alluvial grasslands; and to assess changes in the state of conservation of fluvial appendages (aquatic and amphibious vegetation). A fourth objective, to assess changes in the hydromorphological parameters that influence alluvial environments, is currently being discussed with the partners, with the aim of integrating abiotic indicators into this panel.
Reconciliation of the issues associated with the alluvial forests of the built_up margins of the Rhône and the ecological restoration of the river : questions and perspectives
MOIROUD Christophe, GUÉRIN Stéphane, JANSSEN Philippe, AIRD Adeline, BIANCHIN Nicolas
France
Short abstract : The 2002-2003 major floods led to a conceptual breakthrough in the ecological restoration of the Rhône, highlighting the need to think more in terms of “processes” linked to alluvial dynamics, and therefore to intervene on the river’s built-up margins. The dismantling of the Girardon structures cannot take place without the removal of the woody vegetation that has grown there. The ambivalence of the need to fell trees in order to allow pioneer species regeneration may raise questions, as trees appear in many respects to be a significant theme for several stakeholders. Tree conservation issues encourage, for ecological restoration projects on the Rhône, the pursuit of better integration of this type of alluvial forest. The reconciliation of multiple issues relies on the state of scientific knowledge and on participation in achieving the objectives of conservatories’ programs (in particular, the national action plan for the alluvial forests along the Rhône river and the Beaver Epipactis). Qualitative and quantitative indicators on the condition of these alluvial forests need to be defined as part of the operational monitoring of the river’s ecological restoration led by CNR and its partners. Key issues to explore include water resources, biodiversity and ecosystem functionality, land management and social and landscape value of alluvial forests.
Spontaneous woody community colonization for the Passive Ecological Restoration of a fluvial neo-valley after large dam removal (Normandy, France) – a coupling of ecological and anthropic processes?
LANOË Elven, DUFOUR Simon, LECOEUR Didier, BERNEZ Ivan
France
Short abstract : Dam removal eliminates relying constraints on water and sediment flows as well as living organism’s dispersal. It therefore constitutes a great opportunity to restore riparian ecosystems. The two large hydropower dam removals process, on the Sélune River (Normandy, France) combine two active engineering actions: first, a drawdown of the upstream lake and second, sediment management operations (extraction, storage). In parallel, our research program in restoration ecology is conducted to test a Passive Ecological Restoration (PER) approach aiming at stabilizing the stored sediments and regreening the neo-valley. PER consists in letting woody plant recruitment occur on its own. We surveyed in 2021 the ecological states of woody plant community recruitment at the scale of the neo-valley. We developed an original monitoring methodology to understand how spontaneous vegetation pattern emerges from coupling anthropic actions with various abiotic site conditions and mechanisms of ecological succession. Through the observation of a 2 to 6 years old spontaneous woody communities, PER’s trajectories appear as highly influenced by this chain of previous human decisions interacting with ecological context and lead, at least temporarily, to the establishment of a mosaic of different woody plant communities.
Impact of river channelization structures on the floodplain vegetation state in a mountain river valleys
ZIELONKA Anna, HAJDUKIEWICZ Hanna, HAJDUKIEWICZ Maciej, WALUSIAK Edward
Poland
Short abstract : Riparian ecosystems are highly sensitive to anthropogenic disturbances, particularly river channel modifications, which alter hydromorphology and floodplain vegetation. Channelization and incision create drier floodplain conditions, favoring the dominance of invasive species while reducing native species diversity. As part of the project, we are studying the condition of riparian vegetation along both channelized and unmanaged river sections in the Polish Carpathians. Our findings indicate that the natural sections exhibit greater species diversity, denser vegetation, and a higher proportion of younger plant age classes. Channelized river sections experienced reduced flooding, which has allowed forests to reach a mature stage and increased the presence of invasive species that outcompete native ones. Multispectral UAV data indicated that invasive species exhibited higher NDRE (Normalized Difference Red Edge Index) values in early spring, stronger temperature correlations and resilience to precipitation variability, unlike native and non-native species, which depended on 20–30 days of cumulative rainfall. These findings highlight the adaptability of invasive species to hydrological and climatic changes in regulated rivers, with climate warming likely accelerating their spread. Restoring natural river channels and flooding regimes is critical to supporting riparian forest resilience and controlling invasive species.