Small Watercourses Research Articles

Unveiling Stage Zero Conditions in the New Forest National Park: A UAV‐Based Structure‐From‐Motion Photogrammetry and LiDAR Approach for Reconstructing an Anastomosing Wet Woodland at the Avon Water

ABSTRACTIn recent years, there have been significant technological advances in uncrewed aerial vehicles (UAVs) and in particular the use of lightweight consumer‐grade ‘drones’. This combined with the development of structure‐from‐motion (SfM) technology has provided river restoration practitioners with a new tool that can be used to give an affordable, repeatable and objective assessment of river restoration projects. In this study, a combined SfM photogrammetry and LiDAR approach is utilised on a section of the Avon water, a small watercourse in the New Forest National Park. Victorian‐era straightening and channelisation has significantly altered the ecological and morphological state of the river system, but recent river restoration projects aim to reverse these effects. Whilst historic maps may be used as a guide to reveal the former alignment, changes in river planform occurred much earlier and these maps may not represent the natural course of the river. High‐resolution orthophotos and 3D photogrammetric models of the site are created that reveal a palaeolandscape consisting of a mosaic of anabranching channels. These are interpreted to represent a former anastomosing wet woodland and ‘Stage Zero’ of the river system. It is inferred that early human habitation and associated land clearance altered hydrological and hydrogeological conditions, reducing floodplain connectivity and promoting single‐threaded planform configurations. This was then followed by the most recent Victorian‐era straightening. The palaeolandscape revealed by the study provides a guide for future Stage Zero river restoration in the New Forest and elsewhere, demonstrating an application of low cost, UAV‐derived photogrammetry in river restoration research.

Riparian buffer strips promote biomass, species richness and abundance of flying insects in agricultural landscapes

Agricultural intensification is debated as one of the major drivers for the decline of insect biodiversity. Agri-environmental schemes (AES) are a common measure to promote biodiversity in agriculture by granting compensational payments to farmers for environmentally friendly practices. In this study we examined the effect of buffer strips of at least 5 m width, adjacent to small watercourses and drainage ditches, on insect biomass and insect species richness in agricultural landscapes. We selected ten arable fields in each of four regions in lower and upper Bavaria, Southern Germany. 25 out of 40 sites had a buffer strip between arable crops and watercourse. Insects were sampled at three time periods (May/June, June/July and August/September) for two weeks each. In each period two samples were collected (one per week). On each site Malaise traps were set up in 5 and 80 m distance to the embankment of the watercourse. Half of the samples was then subjected to metabarcoding and the other half was classified into different insect groups by morphological identification and the number of the individuals for each group was counted. For hoverflies (Syrphidae), individuals were identified at species-level. Data on vegetation structure (cover of grasses and herbs) in the studied riparian buffer strips was collected and correlated with number of species, abundances and biomass of flying insects. The five taxonomic orders with the highest species richness and individual numbers were: Diptera, Hymenoptera, Coleoptera, Lepidoptera and Hemiptera. Diptera dominated hereby with 34% of all species and 81% of all individuals. On average, mixed models indicated 31% higher insect biomass, 15% higher species richness and 29% higher individual numbers of flying insects in buffer strips at 5 m distance to the watercourse compared to sites with no buffer strip. The effect was even stronger for butterflies (32% higher species species richness, 70% more individuals) and hoverflies (24% higher species richness, 51% more individuals). In the presence of a buffer strip significantly higher numbers were found for total individuals, Diptera, Hymenoptera and Coleoptera. In 80 m distance to the watercourse, the samples of flying insects were not significantly influenced by a riparian buffer strip. This study highlights the importance of buffer strips in agricultural regions and their multifunctional potential in fostering biodiversity additionally to their acknowledged use for water protection. Ideally, buffer strips are rich in herbs and inflorescences and are therefore beneficial for the insect fauna by serving as valuable habitat with high potential connectivity at landscape level.

Flood risk assessment of a small river with limited available data

Flood risk modeling of small watercourses is challenging when only limited input data are available. Therefore, this study assessed the flood characteristics of a small river (Tarna River: entire watershed-C, upper-VS, middle-TMS, and lower section-TOS) from 1990 to 2019. The assessment focused on modeling, model calibration, and validation using feature event-based time-series data in data-scarce environments. We showed that since the 2000s, the number of high-water levels above 250 cm, and the frequency of three flood types had increased. Flood simulation results showed the largest flooded area in the TMS section, followed by the VS, and then the TOS. The outcomes from the VS, TMS, and TOS sections did not exhibit superior performance compared to the C area. Models performed well for larger flood events, with Kling Gupta Efficiency corresponding well to NRMSE and Nash-Sutcliffe efficiency metrics. Accordingly, flood events characterized by the longest duration and high-water levels yielded outstanding results across all areas, followed by moderate flood events with good accuracy. Normal water level events exhibited significant deviations from the reference across all sections. In summary, despite the event-based modeling challenges in data-limited environments, such models can still mitigate potential flood events and improve decision-making processes.

An assessment of maintenance works and their impact on macroinvertebrate communities and long-term recolonization to small lowland watercourses

Due to their small size and high anthropogenic pressure, small watercourses are particularly prone to severe siltation and are densely overgrown with macrophytes. Many of these watercourses are subject to regular maintenance works (RMW), consisting of seasonal desilting and vegetation clearance, in order to ensure unobstructed water flow. The aim of the study was to assess the impact of three types of maintenance works: dredging and mud removal (DMR), river channel vegetation removal (RCVR) and river bank vegetation removal (RBVR) on taxa species richness, macroinvertebrate density and the Shannon-Wiener diversity index, as well as their changes and long-term benthic recolonization one and two years after completion of the works. The study was carried out in 21 habitats on eight rivers in the European Central Plains Ecoregion. A total of 107 zoobenthic taxa were found at all sites, and their species composition was characteristic of highly hydrophytic waters with low hydrological and hydrochemical quality parameters. A significant decrease in macroinvertebrate taxa richness was observed one year after the works, as the average number of taxa had dropped from thirteen to eight, with a further fall to seven taxa two years after the RMW. The same was true for density, which had decreased from an average of 2496 to 786 individuals per square meter one year after the RMW, while, a gradual recolonization was recorded two years after the RMW, with an average density of 1295 individuals per square meter. The Shannon-Wiener index, which had averaged 2.528 before the RMW, also decreased, falling to 1.982 and 1.832 one and two years after. BACI statistical analyses showed that of the three types of maintenance work, desilting and bottom sediment removal had the largest negative impact, significantly reducing taxonomic composition (by an average of 53%), density (by an average of 43%), and ecological index values (by an average of 40%). Over-frequent maintenance can prevent macroinvertebrate populations from recovering, thus depleting the environment of valuable taxa, including those that provide food for fish and other vertebrates.

The Role of Urban Design in Creating Resilient Public Open Spaces Surrounding Urban Small Watercourses: A Case Study of the Kumodraz Stream in Belgrade

The Role of Urban Design in Creating Resilient Public Open Spaces Surrounding Urban Small Watercourses: A Case Study of the Kumodraz Stream in Belgrade

Macrozoobenthos in the estuary of the small salmon river of Sakhalin Island on example of the Gornaya River

Estuaries as a connecting link between freshwater and marine ecosystems play a special role in salmon rivers. The success of adaptation of juvenile salmonids during the transition to the marine period of life depends on the conditions in estuaries. The work continues the previously started series of publications on the rivers of Sakhalin Island. Using the example of one of the small watercourses in the southeastern part of the island, the hydrological parameters and the structural organization of benthos communities in the atypical estuary have been considered. In the absence of storm surges, penetration of sea water into the water body does not occur; at high tide, water with a salinity of more than 12 psu is observed only at the mouth at the bottom; at low tide, the estuary is completely filled with water with a salinity of 0.1 psu and lower. Studies of the hydrological regime and composition of the bottom fauna were carried out in July 2022. Zoobenthos samples were taken along the longitudinal profile of the estuary at five sections (75 samples in total). Most of the estuarine reach is inhabited by species characteristic of the lower parts of the island watercourses. High environmental variability determines the formation in the estuary of young and unstable benthos communities represented by rapidly reproducing small-sized species.

Approaches to assessment of the total nitrogen and phosphorus inflow into the Neva Bay using the example of the Krasnenkaya River and the Dudergofskiy Channel

There is a necessity for the Baltic Sea environmental protection against toxic contamination and anthropogenic eutrophication. The protection proposes an annual evaluation of the total nitrogen and phosphorus income into the Neva Bay from St. Petersburg. The evaluation takes into account the substances, which inflow into the Neva Bay with water of the Neva River and its spill streams. However, an additional source of the substances is the substances inflow by runoff from watercourses entering Neva Bay. The watercourses do not have monitoring points. There is an additional source of the elements, which is the nonpoint dispersed outflow of the substances from the Neva Bay shore. The paper presents the evaluation methodology of the nitrogen and phosphorus outflow of catchment areas without monitoring points and the methodology verification result. The methodology uses data of analogous watersheds with close spatial structure, drainage network density, and average slope and so on. The methodology includes application of GIStechnologies and cluster analysis. The paper presents some results of the total nitrogen and phosphorus income into the Neva Bay with runoff of two small watercourses.

Long-term dynamics of erosion and channel processes on the territory of Udmurtia

This paper presents the data of long-term observations of gully erosion (1978-2023) and channel processes (2000-2023) on the territory of Udmurtia. Quantitative indices of gully top growth rates at 28 sites for different periods have been compared by types and composition of eroded. Average and maximum rates of their growth are given here. The study of river channel scour at 55 sites in different landscapes has been resulted. To analyze the results, the rivers have been divided into 4 groups according to the magnitude of their orders (according to A. Scheidegger's model). Linear, area and volume indices of scour in ravines and channels of small watercourses have been calculated on the basis of geodetic surveys using electronic total stations and unmanned aerial vehicles.

ПЕРЕХОДНЫЙ ПЕРИОД В ПЕРЕСТРОЙКЕ СИСТЕМЫ ВЛАГООБОРОТА ВОДОСБОРОВ (ПО ДАННЫМ ВОДНОБАЛАНСОВОЙ СТАНЦИИ КАМЕННАЯ СТЕПЬ)

The aspects of adaptating the moisture circulation system at the catchments of small watercourses to climate change based on the observational data from the Kamennaya Step' water balance station are considered. It is demonstrated that the transformation of the moisture circulation system results from the changes in the balance between the groundwater recharge and leakage with a decrease in the contribution of cryogenic factors to the river basin water regime formation. It is suggested that the transition period in the moisture circulation restructuring in river basins can be divided into two periods: with predomination of groundwater recharge and with predomination of its leakage. The length of the transformation phase in the steppe zone depending on the cryogenic factor is about 40 years. The final stabilization of the hydrological regime will depend on setting the groundwater balance under the specific hydrogeological conditions and anthropogenic load.

Mapping the flood hazard potential of small watercourses in a mountain river basin

AbstractThis study presents a methodological approach for the mapping of the flood hazard potential of small watercourses, based on their hydromorphological attributes, on the example of a mountain river basin in Slovakia. The flood hazard of a watercourse is understood more comprehensively, providing a set of influencing variables and their attributes that affect the flood hazard. The proposed procedure consists of several steps ranging from the selection of stream variables influencing the flood hazard potential to the evaluation of the attributes of the variables in terms of their impacts on the flood hazard and the determination of a flood hazard index. The mapping divides the watercourse into reaches that differ by their level of flood hazard potential. This enables us to identify those river reaches that are critical in terms of flood hazard and that require management interventions. The results are interpreted in the context of cadastral areas through which the watercourses flow, which is particularly important for local authorities.

How do Different Types of River Maintenance Works Affect the Ichthyofauna of Small European Watercourses?

Abstract Watercourses serve the needs of agriculture in certain sections and are subject to strong anthropopressure. When agriculture prevails in the catchment, it often has abundant vegetation, macrophytes in particular, and the bottom is covered by a substantial layer of silt. In order to ensure patency of flow and access to water, small watercourses are very often subject to river maintenance works. The aim of the study was to assess the impact of 3 types of works on the diversity of fish species and density of fish in the 1 and 2 year after the works at 21 sites located on 8 rivers in the European Central Plains Ecoregion. As a result of the works, especially in the 1 year after the works, significant changes were found in hydrochemical and hydrological parameters, especially with the increase in velocity and mean depth in watercourses. Additionally, habitat change contributed to differences in the composition of the ichthyofaunal. After 1 year, the diversity of fish species and fish population density increased or remained unchanged after dredging and removal of plants from the river channel, but they decreased after the removal of macrophytes from river banks. After year 2, a decrease in the diversity of fish species and density was observed, associated with re-infestation and siltation of the watercourses. Particularly in the case of dredging and removal of macrophytes from the river bank, maintenance works should not be done too frequently, because some species of natural value disappear.

ENVIRONMENTAL, SOCIAL AND OTHER NON-PROFIT IMPACTS OF MOUNTAIN STREAMS USAGE AS RENEWABLE ENERGY RESOURCES

<p>The main subject of this manuscript is mountain streams used by construction of small hydro power plants. The motivation for this research stemmed from a number of conflicting opinions about the justification of the construction of small hydropower plants and their facilities. This research encompasses different methods for the analysis of the justification of the construction of a small hydropower plant, starting from tradition in correlation with water mills, through a techno-economic approach to a complex multi-criteria research model. All methods are represented by objective formulas.</p> <p>World experiences are also presented, through the level of potential utilization, compared to the degree of development. The possible positive and negative impacts of the construction of such facilities for the exploitation of the potential of small watercourses were analyzed. After the conducted research, and with respect to the principle of minimum energy, which has become the paradigm of modern civilization, it can be concluded that using the potential of small watercourses by building small hydropower plants belongs to the domain of using renewable energy sources and that it is a function of sustainable development.</p> <p>Decision makers are recommended to exclusively apply a multi-criteria methodology, which can holistically include all technical, economic, environmental, social and other non-profitable but important impacts.</p>

Past and present: changes in the Odonata fauna of small lowland watercourses.

Small lowland watercourses, strongly exposed to anthropogenic activities and climate change, have received negligible odonatological attention. This study provides a revised checklist of three typical lowland small watercourses (Kállai-főfolyás, Konyári-Kálló and Ölyvös) within the Pannonian Lowland and presents the changes in their diversity over the past decades. Results revealed a significant biodiversity loss, with a 31.6% decline in Odonata fauna over the last 53 years. The upper and middle sections degraded the most, where the habitats have dried out or become intermittent. However, a diverse Odonata assemblage (1,277 individuals of 27 species) was observed at the 14 sampling sites of the three watercourses, containing protected and sensitive species (Somatochloraflavomaculata, Orthetrumbrunneum, Aeshnaisoceles, Libellulafulva). However, the low abundance of larval and exuvial forms (59 individuals of 13 species) suggests that the majority of the observed adults were developed in other watercourses. While recolonisation from nearby habitats is still possible, a parallel degradation of adjecent waterbodies could lead to an irreversible biodiversity loss.

A holistic approach to the spatio-temporal variability investigation of the main river water quality – The importance of tributaries

The surface water pollution can cause serious ecological disasters. An example is large-scale fish deaths due to excessive salinity, which is global problem. In order to prevent such situations, it is necessary to carry out regular monitoring of both main rivers and their tributaries. The current monitoring system is neither adapted to the variability associated with the diversified use of catchments nor to changing climatic conditions. The Bzura River is one of the most anthropogenically transformed Polish rivers. So far, no comprehensive assessment of the chemical status of its catchment has been carried out. The presented research is a continuation of the study of the spatio-temporal variability of the Bzura chemistry. It covered 19 tributaries within the boundaries of the Łódź Voivodeship. Samples were collected once a month for one hydrological year. In total, 228 samples were obtained, in which 21 parameters were measured. Spatio-temporal variability of water quality on the basis of coefficients of variation (CVs) and water quality indices (WQIs) was evaluated. Principal component analysis (PCA) and cluster analysis (CA) were also performed. In addition, the datasets were visualized using geochemical maps. Combined monitoring with geospatial analysis brings benefits in terms of efficient control and management of water resources. The tributaries were divided according to the degree of their pollution. It was found that the electrical conductivity and concentrations of dissolved oxygen, nitrates, calcium and magnesium differentiated the tributaries in terms of pollution the most. The strong salinity from agricultural and geogenic sources was found. The WQIs were higher for the tributaries than for the Bzura. It suggests that the Bzura may be polluted by the tributaries under “favorable” climatic and hydrological conditions. Therefore, smaller watercourses should be included in monitoring and become more important in terms of an effective solution to global problem of surface water pollution.

Mapping Small Watercourses from DEMs with Deep Learning—Exploring the Causes of False Predictions

Vector datasets of small watercourses, such as rivulets, streams, and ditches, are important for many visualization and analysis use cases. Mapping small watercourses with traditional methods is laborious and costly. Convolutional neural networks (CNNs) are state-of-the-art computer vision methods that have been shown to be effective for extracting geospatial features, including small watercourses, from LiDAR point clouds, digital elevation models (DEMs), and aerial images. However, the cause of the false predictions by machine-learning models is often not thoroughly explored, and thus the impact of the results on the process of producing accurate datasets is not well understood. We digitized a highly accurate and complete dataset of small watercourses from a study area in Finland. We then developed a process based on a CNN that can be used to extract small watercourses from DEMs. We tested and validated the performance of the network with different input data layers, and their combinations to determine the best-performing layer. We analyzed the false predictions to gain an understanding of their nature. We also trained models where watercourses with high levels of uncertainty were removed from the training sets and compared the results to training models with all watercourses in the training set. The results show that the DEM was the best-performing layer and that combinations of layers provided worse results. Major causes of false predictions were shown to be boundary errors with an offset between the prediction and labeled data, as well as errors of omission by watercourses with high levels of uncertainty. Removing features with the highest level of uncertainty from the labeled dataset increased the overall f1-score but reduced the recall of the remaining features. Additional research is required to determine if the results remain similar to other CNN methods.

General patterns of beavers’ selective foraging: how to evaluate the effects of a re-emerging driver of vegetation change along Central European small watercourses

Along small watercourses, the growth and renewal of native willows and poplars (Salicaceae species) are hindered by the effects of past and recent man-made landscape alteration and climate change, while the selective foraging of the beaver (Castor fiber) is also becoming an increasingly important driver. Knowledge about foraging decisions can refine predictions about vegetational processes and help to develop better nature conservation and forest management strategies. We surveyed the woody plant supply (13,304 units) and its utilization by the beaver at 11 study sites along Central European small watercourses, at two fixed distances from the water. We collected information about the taxon, trunk diameter, and type of utilization (cutting, carving, debarking) of each unit. We built (generalized) linear mixed models aimed at answering questions regarding taxon and diameter preference, their interrelatedness, and their importance in foraging decisions. All of the factors examined had a significant effect on foraging decisions. Utilization was mostly explained by the taxon, with Salicaceae species being generally preferred and utilized in all diameter classes with a high ratio. Several further genera were frequently utilized (mainly Cornus and Ulmus), while others were almost completely avoided (including invasive Amorpha and Robinia). The beavers preferred units with a diameter of 5–9 cm. The type of utilization depended primarily on diameter class. Because native softwoods are the most affected by beaver impact, regardless of trunk diameter, their survival and regrowth should be consciously supported by increasing the water table and improving hydrological conditions.

Studying the Composition and Genesis of Organic Matter in Bottom Sediments of Polluted Small Watercourses in Khabarovsk City Territory

Studying the Composition and Genesis of Organic Matter in Bottom Sediments of Polluted Small Watercourses in Khabarovsk City Territory

Studying the Composition and Genesis of Organic Matter in Bottom Sediments of Polluted Small Watercourses in Khabarovsk City Territory

The distribution of organic matter, hydrocarbons, phytopigments, and ecological-trophic groups of microorganisms was studied in the bottom sediments of ten small tributaries of the Amur R. near Khabarovsk. The water showed high concentrations of organic matter, varying from 44.47 to 279.3 mg/L. The concentration of Corg in bottom sediments varied from 1.9 to 23.1% in different types of sediments; the amount of hydrocarbons reached 5081 mg/kg, exceeding the background level by a factor of up to 50. Studies of the molecular composition of hydrocarbons in sediments revealed in some streams the predominance (up to 100% of the total) of light (C8–C13) n-alkanes, typical of oil products and the products of vegetation combustion. High-molecular compounds dominated in HC composition in most watercourses, including n-alkanes, genetically associated with terrestrial vegetation, and heavy fractions of oil products with various levels of microbial degradation. Volatile organic compounds were quantitatively dominated by the products of microbiological transformation (acetaldehyde and methanol). In terms of the concentration of sedimentary pigments (up to 400 µg/g), the sediments of the majority of watercourses belong to the hypereutrophic type. The total abundance of microorganisms in water varied from 2.7 to 488.0 thousand CFU/mL; in sediments, it was distributed symbatically, but ranged from 0.1 to 19.3 million CFU/g. The number of heterotrophic bacteria in bottom sediments correlated with the parameter of overload of the self-purification capacity (r = 0.718), and the number of oil-oxidizing bacteria correlated with hydrocarbon concentration (r = 0.967), thus confirming the indication properties of this bacterial group.

AMI-KMNP dataset: Occurrence records of aquatic macroinvertebrate species from a 10-year-long biodiversity survey in SE Hungary

We outline a 100% georeferenced dataset of aquatic macroinvertebrate occurrence records collected from the operational area of the Körös-Maros National Park Directorate (SE Hungary) between 2012 and 2021. The species-level dataset includes 25,935 records of 644 taxa from 625 localities of wide variety of freshwater habitats from soda pans to lowland marshes and small watercourses to medium-sized and larger rivers. Four non-biting midge species are reported for the first time from the Hungarian fauna. The dataset is available through the Global Biodiversity Information Facility (GBIF).

Processes of Natural Self-Cleaning of Small Watercourses with Increasing Anthropogenic Load in the Dniester River Basin

Processes of Natural Self-Cleaning of Small Watercourses with Increasing Anthropogenic Load in the Dniester River Basin