Scour Features at Wood Bundles

Structures like blunt-nosed chevrons, log deflectors and double-winged log frames help in modifying the flow regime in the channel by concentrating the flow and increasing navigability. Moreover, they create scour pools in the downstream stilling basin, which can be used either as fish refuge or as an in-stream storage site for previously dredged material. In this respect, the use of wood debris in the channel in the form of wood bundles has gained attention for the ability of these structures to integrate into the surrounding fluvial habitat and to divert the flow partially towards the central part of the channel when placed in curves. Considering the absence of studies dealing with wood bundles as a restoration structure, the aim of this paper is to analyse the scour mechanism and equilibrium scour morphology of wood bundles in straight and curved channels. In doing so, a wide range of hydraulic conditions, structure positions and configurations were tested. Thereafter, dimensional analysis was carried out to derive useful empirical relationships to predict the maximum scour depth and length as well as the maximum dune height based on a novel, equivalent Froude number, which accounts for the effects of channel curvature and structure position. Moreover, the various resulting scour morphology types were classified, and conditions of their existence were determined depending on the abovementioned Froude number and other key hydraulic parameters.

RANDOM FOREST-BASED RIVER PLASTIC DETECTION WITH A HANDHELD MULTISPECTRAL CAMERA

Plastic pollution has become one of the main global environmental emergencies. A considerable part of used plastics materials is dispersed or accumulated in the environment with a significant damaging impact on many terrestrial and aquatic ecosystems.Artificial Intelligence has proven a fundamental approach in last years for the detection of plastics waste in the aquatic habitats: several groups have recently tried to tackle such problem by developing some machine learning-based methods and multispectral or RGB imagery. This study compares the results obtained by two machine learning classifiers, namely Random Forests and Support Vector Machine, to detect macroplastic in the fluvial habitat through multispectral imagery. The acquisition of images has been made with a hand-held multispectral camera called MAIA-WV2. Despite the obtained results are quite good in terms of accuracy in a random validation dataset, some issues, mostly related to the presence of white rocks and glares on water have still to be properly solved.

Natural Fluvial Ecohydraulics

Ecohydraulics is the study of the mechanisms that explain hierarchically nested aquatic and riparian biotic phenomena. Mechanisms are sequential actions that can be physical, biological, or an interaction between the two. Biotic phenomena consist of individual, population, and community-level conditions, behaviors, and interactions. Hierarchical nesting means that phenomena are present across a wide range of spatial scales: from the smallest fluid continuum scale to the scale of the entire Earth. Many ecohydraulic studies prominently address scaling. Under this definitional framework and given the widespread occurrence of water on Earth, ecohydraulics is the “proximal” science mediating the influence of “distal” landscape drivers (e.g., climate, geology, and topography). Historically, scientists discovered empirical correlations relating biotic conditions to both proximal and distal abiotic variables. However, when such results are applied to practical societal problems (e.g., stream barrier passage, habitat rehabilitation, and flow regime specification), the accuracy and specificity is insufficient to solve them. That has led to widespread recognition of the need for a mechanistic understanding culminating in predictive numerical models. Driven by such necessity, physical and biological scientists and engineers have formed multidisciplinary teams to work out how water and biota interact. Through its marriage of conceptual understanding with quantitative analysis, ecohydraulics is playing a central role in methodological advancements to objectively, transparently, and repeatably explain biotic phenomena at multiple spatial scales. Students involved in ecohydraulics are part of an emerging interdisciplinary generation identifying more with problem-oriented applied science that responds to societal needs to solve specific ecological problems than disciplinarians driven by curiosity and traditional socio-scientific pathways. Nevertheless, it goes too far to conclude that ecohydraulics is nothing more than the application of other sciences, with no basic developments of its own. Necessity often motivates ecohydraulicists to undertake novel experiments revealing fundamental discoveries. As a result, a reasonable distinction can be made between basic ecohydraulics for studying natural phenomena and applied ecohydraulics for rehabilitating degraded phenomena. This annotated bibliography is the first of two spanning ecohydraulics, and it tackles the former, while the second addresses the latter. Due to space limitations, this article is narrowed to natural fluvial ecohydraulics. Within this domain, there are five essential topics: environmental fluid mechanics, flora ecohydraulics, fluvial habitat, faunal ecohydraulics, and fish migration. Finally, space limitations further limit the scope to an emphasis on observational studies over numerical modeling.

The importance of fluvial habitats for amphibian conservation in the Mediterranean climate

The importance of standing water habitat for amphibians is widely known and recognized. However, in some arid or semiarid zones the availability of these temporal habitats is uncertain and fluvial habitats could play a very important role for amphibian conservation. For example, in the Mediterranean region many fluvial habitats have a temporary character, lacking predatory fish populations and hosting diverse amphibian communities. To compare the relative importance of various fluvial and still water habitats, we studied the breeding amphibian community over a wide area from 2006 to 2008 in southwestern Spain. All amphibian species found in the area were present in lotic habitats and the highest amphibian diversity was found in temporary stream habitats. Fluvial habitats were among the most important habitats used for reproduction by eight amphibian species of conservation concern, whereas for seven species a significant positive selection was found towards one or several fluvial habitat types as reproduction habitats. The conservation of fluvial habitats including rigorous impact assessments and management programs can be very important for the conservation of endangered amphibians in these semi-arid areas.

Impact of potash mining in streams: the Llobregat basin (northeast Spain) as a case study

Potash mining is significantly increasing the salt concentration of rivers and streams due to lixiviates coming from the mine tailings. In the present study, we have focused on the middle Llobregat basin (northeast Spain), where an important potash mining activity exists from the beginning of the XX century. Up to 50 million tonnes of saline waste have been disposed in the area, mainly composed of sodium chloride. We assessed the ecological status of streams adjacent to the mines by studying different physicochemical and hydromorphological variables, as well as aquatic macroinvertebrates. We found extraordinary high values of salinity in the studied streams, reaching conductivities up to 132.4 mS/cm. Salt-polluted streams were characterized by a deterioration of the riparian vegetation and the fluvial habitat. Both macroinvertebrate richness and abundance decreased with increasing salinity. In the most polluted stream only two families of macroinvertebrates were found: Ephydridae and Ceratopogonidae. According to the biotic indices IBMWP and IMMi-T, none of the sites met the requirements of the Water Framework Directive (WFD; i.e., good ecological status). Overall, we can conclude that potash-mining activities have the potential to cause severe ecological damage to their surrounding streams. This is mainly related to an inadequate management of the mine tailings, leading to highly saline runoff and percolates entering surface waters. Thus, we urge water managers and policy makers to take action to prevent, detect and remediate salt pollution of rivers and streams in potash mining areas.

Impacts of urbanisation level and distance from potential natural mosquito breeding habitats on the abundance of canine dirofilariosis

Dirofilariosis is an emerging mosquito-borne veterinary and medical problem in the Northern hemisphere. The ecological investigation of 56 canine dirofilariosis cases in new endemic locations was performed in Szeged, Hungary. The aim was to analyse the influence of the spatial patterns of dog abundance and the potential mosquito breeding habitats on the spatial occurrence patterns of dirofilariosis in the city of Szeged. The limnoecological characterisation was based on the fluvial habitat classification of Amoros of natural water bodies; the built environment was evaluated using the UrbanisationScore urbanisation intensity measuring software. Dirofilaria immitis accounted for 51% and D. repens for 34.3% of the dirofilariosis cases, and in 20% of the cases only the Knott’s test was positive. It was concluded that most of the cases were related to locations with a medium to high urbanisation index, although the proximity of mosquito-bearing waters also played an important role in the observed spatial infection patterns. We found that the distance from potential mosquito habitats and the urbanisation intensity determine the abundance of dirofilariosis in urban environments.