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.
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 : (Micro)plastics in rivers
Assessment of pollution generated by macro-waste from sanitation networks, an experiment within Lyon Metropole
DARMON Gaëlle, GOUTALAND David, MOREIRA Sylvain, PORTALIER Romain, BRIAND-PONZETTO Claudie, KHAMLA Karim, LEBLANC Olivier, LACAILLE Samuel, LANDAIS Patrice
France
Short abstract : Wild macro-waste is a scourge for the environment and generates significant economic and health costs. Often transported by runoff water and sanitation networks, it affects rivers and biodiversity. Lyon Metropolis has initiated a project aimed at reducing macro-waste in its hydrographic networks. An experiment in a sanitation network using retention nets allowed for the quantification and characterization of waste, with wipes representing the majority of the waste collected. Although several factors are likely to influence the observed flows, this experiment showed that the quantities of wipes, on average 60 per hour during wastewater peaks, are highly significant. The quantities discharged are much smaller, but still significant (at least 6 wipes/day). Often made of plastic, they cause significant landscape, environmental, and safety issues. Curative solutions like retention nets are difficult to maintain for the long-term due to logistical constraints. Therefore, it is essential to implement upstream measures, such as stricter regulations on the composition of disposable products and the promotion of alternative solutions, as well as awareness-raising actions.
Plastigiessen : Global quantification of plastic debris in a peri-urban river (Steingiessen – Strasbourg)
CHARDON Valentin, WENGER Romain, KELLER Benjamin, GRIMMER Gauthier, ESCHBACH David
France
Short abstract : Over the last decade, numerous studies have been carried out to quantify plastic litter pollution in hydrosystems. The vast majority of these studies focus on one type of flow and too few take a global view (floating litter, litter in the water column and in the sedimentary matrix). This study, carried out on a peri-urban river (Steingiessen) in the Eurometropole of Strasbourg, aims to partially fill this gap through innovative multi-methods monitoring. The aim of this medium-term project is to provide optimal management solutions for plastic waste flows in the Steingiessen and to analyse the potential transferability of this study to other alluvial sites with similar problems.
Assessing the Use of AI to Quantify Plastic Pollution in Rivers : From Technological Innovation to Action in the Field.
ALLOU Sabine, LEROUX Clément, OLLION Charles
France
Short abstract : The Surfrider Foundation has explored the use of artificial intelligence to map and quantify plastic pollution in European rivers. Its aim is to empower citizens to contribute to data collection efforts by using the smartphone app Plastic Origins to film riverbanks during kayaking excursions. The AI model developed, named Surfnet, analyses these videos to detect macro-waste by combining computer vision technologies with video tracking. The use of AI enables better standardised and larger-scale data collection as compared to manual methods, which are often prone to observational errors. A training dataset of 5,000 labelled images was created with the help of volunteers, and techniques such as data augmentation were used to enhance performance. The project also highlights a frugal approach by using TinyML technologies to minimise both the financial and environmental costs of AI, particularly by reducing dependency on cloud-based operations. While the project effectively raises awareness about plastic pollution among citizens and decision-makers, challenges remain, both in the field and technologically, to make it a true diagnostic tool.