Journal: Journal of Ecohydraulics

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Taylor & Francis

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ISSN

2470-5357

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2016 - 201922020 - 20258
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Publications 1 - 10 of 10
  • Early careers on ecohydraulics: challenges, opportunities and future directions
    Item type: Journal Article
    Wilkes, Martin A.; Neverman, Andrew J.; Casas-Mulet, Roser; et al. (2016)
    Journal of Ecohydraulics
  • Quantifying fluvial habitat changes due to multiple subsequent floods in a braided alpine reach
    Item type: Journal Article
    van Rooijen, Erik; Siviglia, Annunziato; Vetsch, David F.; et al. (2024)
    Journal of Ecohydraulics
    During flood events, river topography and fluvial habitats can change drastically, potentially affecting the ecological status. In case of multiple floods, whether each single event modifies the habitat characteristics in the same direction or not, is still an open question. We gathered high quality topographical data of one braided Alpine reach before, between and after multiple floods. Considering the full dynamics of the hydrological regime affected by hydropower production, we calculated water depth and flow velocities distributions for relevant discharge conditions using hydrodynamic modelling. We then calculated four ecological indicators related to habitat diversity, habitat quantity, habitat connectivity and stranding risk. Despite the consistent depositional morphological trend, the habitat diversity and stranding metrics returned to pre-floods values after an initial deviation. The habitat quantity and connectivity metrics did not show a clear trend towards an alternative state. Habitat prevalence varied seasonally and with hydropower water release, and also changed markedly between floods, possibly affecting species composition. We show the possible intrinsic variability in several ecological indicators which can aid in the management and restoration of river floodplains.
  • Fish guidance structures: hydraulic performance and fish guidance efficiencies.
    Item type: Journal Article
    Albayrak, Ismail; Boes, Robert; Kriewitz-Byun, Carl R.; et al. (2020)
    Journal of Ecohydraulics
    The hydraulic performance and fish guidance efficiency (FGE) for behaviourally-based mechanical fish guidance structures, i.e. louvers and modified angled bar racks (MBRs), were evaluated experimentally and the results are presented herein. Detailed velocity profiling was conducted to assess the hydraulic performance of the 1:1 Froude-scaled racks in an etho-hydraulic laboratory flume. Guidance efficiencies of the studied rack configurations were evaluated through live-fish tests in the same flume. Tests were conducted with five European fish species, namely, barbel (Barbus barbus), spirlin (Alburnoides bipunctatus), European grayling (Thymallus thymallus), European eel (Anguilla anguilla) and brown trout (Salmo trutta). The results demonstrate that MBRs are advantageous over louvers because of reduced head losses, improved hydraulics and higher FGEs. Furthermore, use of a bottom overlay on the MBRs substantially increased the FGE. The results are discussed and compared with literature data. Recommendations for an optimized and economic MBR design are given. The present findings underpin the follow-up studies for further optimization of MBR design.
  • How does sediment supply influence refugia availability in river widenings?
    Item type: Journal Article
    Rachelly, Cristina; Mathers, Kate L.; Weber, Christine; et al. (2021)
    Journal of Ecohydraulics
    Habitats that mitigate the effects of a disturbance event (e.g. flood) are referred to as refugia. Their occurrence in heavily impacted river systems is often limited, and their restoration rarely pursued. This paper presents the results of a combined laboratory and numerical modeling study to assess flood refugia availability to mobile aquatic organisms in the context of river restoration and dynamic river widening. We used a calibrated 2D hydrodynamic model based on eight topographies obtained in laboratory experiments to assess refugia availability by analyzing the hydro-morphological conditions under varying sediment supply. Overall, sediment equilibrium sustains more complex hydro-morphological conditions with low bed shear stress zones being maintained during elevated discharges. Furthermore, our results suggest that the floodplain is an important potential refuge that becomes accessible for discharges with a return period of approximately one year. Conversely, sediment deficit results in a homogeneous flow field with steadily increasing hydraulic forces for high flows and impaired lateral connectivity except for very large flood events of a 30- to 100-year return period. Dynamic river widening implemented in a channel with sediment equilibrium conditions as opposed to a sediment deficit is thus more likely to provide flood refugia.
  • Patch-scale habitat dynamics: three metrics to assess ecological impacts of frequent hydropeaking
    Item type: Journal Article
    Bätz, Nico; Judes, Clarisse; Vanzo, Davide; et al. (2025)
    Journal of Ecohydraulics
    Human activities significantly alter natural river flows, impacting ecosystem functioning and biodiversity worldwide. Hydropeaking, resulting from intermittent on-demand hydropower generation, introduces sub-daily flow fluctuations exceeding natural variability. While the effects of single hydropeaking events are well-studied, the cumulative impacts of frequent hydropeaking requires further exploration. This study aims to develop metrics that captures changes in habitat dynamics at the patch scale (i.e. individual micro-habitats within the habitat mosaic) due to reoccurring hydropeaking. Using hydrodynamic simulations, we introduce three patch-scale metrics to quantify habitat dynamics with high spatial (0.5 m) and temporal (10 min) resolution: (M1) Habitat probability within patches, assessing spatio-temporal diversity of habitats; (M2) Habitat shifts within patches, evaluating habitat persistence for sessile organisms (e.g. vegetation, invertebrates); and (M3) Spatial shifts of habitats, indicating habitat relocation affecting mobile species (e.g. adult fish). Using eight hydro-morphological scenarios representing different levels of anthropogenic modification of flow and morphology, we demonstrate that these metrics effectively quantify changes in habitat dynamics at patch-scale. The results highlight the ecological relevance of these metrics and their potentially utility for river management. By identifying areas susceptible to ecological impacts, these metrics may serve as tools for hydropeaking mitigation, enabling more targeted and spatially explicit habitat management and restoration.
  • Sampling sufficiency for determining hydraulic habitat diversity
    Item type: Journal Article
    Stähly, Severin; Gostner, Walter; Franca, Mário J.; et al. (2018)
    Journal of Ecohydraulics
  • Effects of channel hydraulics and morphology on water-mediated dispersal in an alpine river
    Item type: Journal Article
    Fink, Sabine; Caponi, Francesco; Vetsch, David F. (2025)
    Journal of Ecohydraulics
    Water-mediated dispersal (hydrochory) connects spatially separated terrestrial and aquatic communities, facilitating the movement of reproductive materials and organisms through river networks. Anthropogenic pressures and climate change have altered these dynamics, potentially affecting biodiversity. Although dispersal distances and landing mechanisms are commonly attributed to interactions between channel flow, morphology, and particle properties, these relationships remain poorly investigated, especially in alpine rivers. We conducted field experiments in an 80-m-long channel of a braided river floodplain in Switzerland, releasing wooden cylinders as plant propagule mimics at three discharge rates. We used a 2D depth-averaged numerical model to quantify hydraulic variables and link them to measured particle travel distances and landing sites. We found that the number of floating particles decayed exponentially with distance, with decay rates primarily related to discharge. The deposition patterns were dictated by channel morphology rather than particle size, and the submergence of the river bed at low discharges strongly influenced the landing position. This study emphasizes the impact of small-scale channel heterogeneity on the dispersal of naturally buoyant materials. Our findings may help conservation and restoration measures, identify ecological flows and dispersal hotspots, especially in hydropower-impacted rivers.
  • Why hydropeaking frequency matters: effects of recurring stranding on fish
    Item type: Journal Article
    Hayes, Daniel S.; Bätz, Nico; Tonolla, Diego; et al. (2025)
    Journal of Ecohydraulics
    Research and management of hydropeaked rivers largely overlook the ecological impacts of recurring flow fluctuations, such as fish stranding, on ecosystem health. This article synthesizes scientific and grey literature, field studies, and experiments to assess the effects of frequent hydropeaking on fish. Findings show that hydropeaking frequency significantly affects the ecological integrity of alpine rivers, with an average of three daily down-ramping events. Despite some evidence of behavioral adaptation of fish to recurrent flow fluctuations, this adaptation appears insufficient to counter the cumulative effect of a series of single hydropeaking events. Larval and juvenile fish are particularly vulnerable, with stranding impacts extending to the population and community levels. Effective mitigation should prioritize reducing the cumulative impact of recurring hydropeaks while ensuring single-event ramping rates and flow amplitudes remain within ecological limits. To effectively safeguard sensitive habitats, targeted mitigation efforts informed by an understanding of habitat dynamics are critical. Furthermore, maintaining lateral connectivity within river systems is essential for supporting resilient fish populations, especially where hydropeaking mitigation possibilities are limited. Finally, this study identifies future research directions on hydropeaking frequency and its ecological effects.
  • Behavioural response of chub, barbel and brown trout to pulsed direct current electric fields
    Item type: Journal Article
    Moldenhauer-Roth, Anita; Selz, Oliver M.; Albayrak, Ismail; et al. (2025)
    Journal of Ecohydraulics
    Electrified fish guidance and trash racks at water intakes are a promising technology to divert downstream moving fish away from turbines and towards a safe bypass route. Current recommendations on pulsed direct current (pDC) waveforms to electrify such racks are based on a limited number of field studies, and hence investigations comparing pDC waveforms are needed. To this end, systematic tests of electrosensitivity to pDC waveforms were performed with wild caught brown trout (Salmo trutta), chub (Squalius cephalus) and barbel (Barbus barbus) to determine (1) behaviour types and thresholds exhibited by different species and variation within species families, (2) the effect of fish body size, and (3) optimal parameters of pDC waveforms for possible use at electrified bar racks. Both the peak power density threshold triggering immobilization and twitch reactions decreased with increasing fish size according to a power law relation. Increasing frequency led to lower thresholds for immobilization and higher thresholds for twitch reactions. Though some inter-specific variation was observed, a waveform with a pulse duration of 2 ms and a frequency of 10 Hz was determined to be the most promising for all three species to be tested and possibly used at electrified bar racks.
  • Comparison of electrified vertical trash racks—electric field and effects on species-specific fish behaviours
    Item type: Journal Article
    Moldenhauer-Roth, Anita; Selz, Oliver M.; Boes, Robert; et al. (2025)
    Journal of Ecohydraulics
    Retrofitting existing trash racks at hydropower intakes with electricity may prevent turbine passages of downstream moving fish and allow them to search for an alternative passageway if the installation of fish guidance racks is not feasible. The present study evaluated two types of electrification: (1) using the rack as an electrode and placing an additional row of electrodes downstream and (2) vertical rod electrodes placed either on the front of the bars of the rack, or used individually without combination with a bar rack. We evaluated their fish protection efficiency for a large bar spacing of 90 mm typical for large hydropower plants. Experiments were conducted with wild caught brown trout (Salmo trutta), chub (Squalius cephalus), and European eel (Anguilla anguilla) at approach flow velocities of 0.15, 0.3, and 0.6 m/s. For the large bar spacing tested here, placing an electrode downstream of the rack proved to be more effective than rod electrodes with protection efficiencies of 78–91% for eel and 78–95% for chub depending on the approach flow velocity. Brown trout reacted less sensibly to electric fields than chub and eel and proved difficult to prevent from rack passage.
Publications 1 - 10 of 10