Exploring historical changes in mountain river hydrodynamics induced by human impact.

During the 20th-century many mountain rivers in Europe were subjected to intensive human impacts which substantially modified their channel morphology. How these changes affected river hydrodynamics and response to floods remains uncertain. In this work, we perform hydraulic modelling using data from archival aerial photos to explore relations between hydraulic parameters of floods and human-induced channel incision occurring on the Czarny Dunajec River (Polish Carpathians) between 1964 and 2012. Data on vertical position of the channel used for two-dimensional modelling of flood flows were extracted (as Digital Elevation Models DEMs) from archival aerial photos from 1964 and 1983 and ALS (Airborne Laser Skanning)-derived DEM from 2012. Water depth, flow velocity, bed shear stress, and sediment critical diameter were modelled for four flood scenarios (2-year, 5-year, 20-year, and 50-year floods) as well as the extent of flooded area and additionally the grain size of channel sediment was calculated. The values of water depth, flow velocity, bed shear stress and sediment critical diameter increased significantly between 1964 and 1983, especially for 20-year and 50-year floods. Only the flow velocity within the floodplain zone did not increase for the two largest flood scenarios due to the expansion of riparian forest in the second half of the twentieth century. The increase in flow rate was accompanied by a progressive reduction of the extent of flooded area, especially between 1964 and 1983, as well as by increase in mean grain size of channel sediment. Between 1983 and 2012 changes in hydraulic parameters were less pronounced, and coarser and well packed channel sediment dominated on the river bed. Our work demonstrates that reconstruction of past river hydrodynamics, rather than river state at time horizons, can give essential insights into functioning of the river channel and floodplain during the intensification of human impacts after 1950s.

Body composition and anthropometrics of young male swimmers in relation to the tethered swimming and kinematics of 100-m front crawl race.

BACKGROUND: The aim was to analyze the relationship of body mass and predicted muscle mass of body segments on swimming kinematics and tethered swimming indices, and further assess the influence of those indices on 100-m front crawl performance of adolescent male swimmers. METHODS: In 19 volunteer swimmers (age: 13.5±0.44 years, height: 168.6±7.77 cm, body mass: 56.9±10.57 kg), the predicted muscle mass of body segments was assessed with bioelectrical impedance analysis. The kinematic indices of swimming (stroke rate - SR, stroke length - SL, and stroke index - SI) were calculated from a video recording of a 100-m front crawl race. The strength indices (maximum and average value of force, average impulse per single cycle, force decline) were collected in a 30-second front crawl tethered swimming test. RESULTS: The average tethered swimming force was positively correlated with surface swimming speed (0.505; P≤0.05). Indices of SL, SI were influenced by average impulse per single cycle (0.58, 0.55; P≤0.05), and further the SI was strongly correlated with most specified speed indices of the 100-m race (0.59; P≤0.05). CONCLUSIONS: It can be stated that the ability of force development in a single stroke, owing to strong interrelation with SI, is a good predictor in talent identification among young swimmers.

Hydromorphological evaluation of the river training impact on a multi-thread river system (Belá River, Carpathians, Slovakia).

The paper evaluates the impact of river training works designed to address problems associated with flooding on the braided-wandering Belá River in Slovakian Carpathians. This impact was investigated after the flood event in July 2018 on 11 river reaches where the river engineering and management intervention was applied. We analyzed its impact by spatio-temporal variations in river morphology (12 channel parameters) and changes in cross-section and hydraulic parameters (flow velocity, shear stress, stream power, W/D ratio) between pre- and post-flood management periods. The research hypotheses related to decreasing geodiversity in managed river reaches, a rapid increase in flow velocity during an extreme flood in river reaches where there is no sufficient floodplain inundation due to artificially high banks built by river training works, and increasing erosive force in the channel zone thanks to river management intervention were confirmed. The intervention in the braidplain area of the Belá River resulted in an undesirable simplification of the river pattern, loss of geomorphic diversity, loss of channel-floodplain connectivity, and disturbance and restraint of hydromorphological continuity. Identification of main conflicts of the Belá River management is important for clarifying the different approaches of stakeholders in the study area and aims to provide an objective illustration of their consequences. The presented analyses could help in future management issues as well as in the more critical decision-making process in vulnerable and rare braided river systems on the present when we are losing so many natural rivers by human decisions.

Specific and Holistic Predictors of Sprint Front Crawl Swimming Performance.

The aim of the study was to examine the impact of selected water- and dry-land predictors of 50-m front crawl performance among 27 male swimmers aged 19.3 ± 2.67 years. The following water tests were performed: front crawl tethered arm stroking in a water flume (flow velocity: 0.9 m·s-1) and leg tethered flutter kicking in a swimming pool. Anaerobic tests on dry land included arm cranking and a set of 10 countermovement jumps. The maximal and average forces generated by legs in tethered swimming (Fl max and Fl ave) turned out to be the strongest predictors of sprint swimming aptitude. These values were strongly correlated with total speed (Vtotal50) (r = 0.49, p < 0.05 and r = 0.54, p < 0.01, respectively), start, turn, and finishing speed (VSTF) (r = 0.60, p < 0.01 and r = 0.67, p < 0.01, respectively). The relationship of Fl max and Fl ave with surface speed (Vsurface) was moderate (r = 0.33, non-significant and r = 0.41, p < 0.05, respectively). The maximal force generated by arms (Fa max) during flume tethered swimming significantly influenced Vsurface and Vtotal50 (0.51, p < 0.01 and 0.47, p < 0.05, respectively). Its relationship with VSTF was close to significant (0.36, p = 0.07). Upper and lower limb dry-land tests showed lower and more holistic relationships with the 50-m front crawl race, however, being a good complement to overall fitness assessment. Specific in-water evaluation, especially the newly prepared flutter kicking test, as well as dry-land tests, can be applied to regularly monitor progress in swimming training, and to identify talented swimmers.

Biological Age in Relation to Somatic, Physiological, and Swimming Kinematic Indices as Predictors of 100 m Front Crawl Performance in Young Female Swimmers.

BACKGROUND: Some swimmers reach high performance level at a relatively young age. The purpose of this study is to determine the relationship between adolescent female swimmers' 100 m front crawl race (Vtotal100) and several anthropometry, body composition, and physiological and specific strength indices. METHODS: Nineteen adolescent female swimmers were examined for biological age (BA) and body composition. Oxygen uptake was measured during water-flume stage-test front crawl swimming with ventilatory thresholds examination. Specific strength indices were assessed during 30 s of tethered swimming. Stroke rate (SR), stroke length (SL), and stroke index (SI) were also examined. RESULTS: BA was strongly correlated with anthropometrics and tethered swimming strength indices, and showed moderate to strong correlation with ventilatory thresholds. Speed of swimming in the race was moderately to largely correlated with speed at V˙O2 max-VV˙O2max (r = 0.47-0.55; p < 0.05)-ventilatory thresholds (VAT, VRCP) (r = 0.50-0.85; p < 0.05), SL (r = 0.58-0.62; p < 0.05), and SI (r = 0.79-0.81; p < 0.01). CONCLUSION: Results confirmed a significant role of biological maturation mediation on body composition and body size, ventilatory indices, and specific strength indices. BA was not a significant mediation factor influencing the swimming kinematics (SL, SI) and speeds of VAT, VRCP or VV˙O2 max, which were strong predictors of the 100 m race.

Riparian ground beetles in gravel bed rivers: validation of Invertebrate Bankfull Assessment method.

Bankfull Assessment Method (IBA method) applies riverine invertebrate community of ground beetles as a biotic indicator of bankfull variation in a dynamic river. IBA index is calculated as a proportion of small sized individuals (1-6 mm) to large size individuals (18-24 mm) of ground beetles in given sample site. The aim of the study was to validate the IBA bankfull discharge method with 135 carabid assemblages collected in gravel-bed rivers of various modifications of channel morphology in the Polish Carpathians. Constrained canonical correspondence analysis revealed that biotic factors such as IBA, plant cover and plant height described most of the variation of small and large sized species abundance. The IBA index variation confirmed earlier expectation of the mean IBA values. Mean value of the index for the lowest bench is about 5, for the middle bench about 2 and it never exceeds 1 for the highest bench. The bankfull calculated using morphometric methods (Wolmann) was located between the first and second bench on each river. Values of the IBA for the lowest bench depend significantly on channel incision whereas modifications of vegetation affect the values for all three benches. The study presents high value of IBA method in estimating bankfull discharge which is considered to be important supporting flow predicting morphological changes responsible for river channel shape with direct connection to living organisms occupying river banks as well as to river environmental quality. Proposed simple method could be important for local watershed managers for prediction of bank embankments level (e.g. maximum level of rip-rap or gabions) or for maximum level of low head hydraulic structures when they are necessary in terms of river engineering works but when they are still built as environmental friendly hydraulic structures.

Body composition and specific and general strength indices as predictors of 100-m front crawl performance.

PURPOSE: The purpose of this research was to examine the impact of body composition on the anaerobic ability to generate strength and power produced separately by upper and lower limbs during dry-land and in-water (propulsion force) tests. Further examination included the influence of all gathered anaerobic strength indices on the results of 100-m front crawl race. METHODS: The study involved 26 male swimmers (age: 19.8 ± 2.48 years). Fat-free mass, total body water and muscle mass of arms, legs, and trunk were measured. Dry-land average work, maximal power generated in 40-second arm-cranking test, and work generated in 20 countermovement jumps were evaluated. The forces generated separately by arms and legs were assessed during 40-second tethered swimming. All indices of body composition were found strongly correlated with indices of average work and maximal power generated by arms and legs in dryland tests. RESULTS: Muscle mass of arms and trunk moderately and strongly (r = 0.44-0.64) influenced the force generated by arms in tethered swimming. There was no significance in the relationship of leg muscle mass and force generated by legs in tethered swimming. Significant relationships were observed between the results of the 100-m front crawl and the muscle mass of the arms, trunk, legs, as well as the average work and maximal power in the arm-cranking test (r: 0.39-0.54). The average impulse of arm force and maximal leg force in tethered swimming moderately and significantly correlated with 100-m swimming results. CONCLUSIONS: The study concludes the relevance of developing muscle mass balanced to the body size, which is involved in propulsion force production in sprint front crawl swimming.

Seasonality of mean flows as a potential tool for the assessment of ecological processes: Mountain rivers, Polish Carpathians.

The classification of river catchments according to their hydrological regime is crucial elements of regionalisation. In absence of hydrological data, the regionalisation of catchment method may be used to asses many flows characteristics like regime or design flow and thus provide help in the analysis of hydrological and ecological processes and also in the management of water resources. Correct clarification of catchments requires knowledge about the main factors that influence on river regime, like meteorologic conditions, land cover/land use, geology, soil properties terrain features, human activities. The aim of the study was to analyse the relationship between selected catchment attributes along with precipitation climatology and seasonality of mean flows (MQ) in the mountainous rivers in the Upper Vistula basin (the biggest and the most important river in Poland) and regionalisation catchments based on seasonality index. To achieve the objective of the study, we concentrated on the mountain stream and river catchments that are regionalised to the Upper Vistula basin (all of which are Vistula tributaries) and we employed the Colwell's seasonality index in an attempt to clear up the said ecohydrological measures. The study confirmed that in mountainous catchments, where response time to rainfall is shorter due to larger slopes, higher seasonality of mean monthly discharges, as expressed by the seasonality index M, is observed. In this case, variability of seasonal rainfall affected seasonality of MQ. In case of smaller slopes and large forest cover and catchment areas, seasonality of flows was lower. The innovative aspect of the presented study is the attempt to correlate the Colwell's seasonality index with the physiographic and meteorological characteristics of the catchment. Until now, the characteristics of the catchments have been used as factors differentiating the hydrological regime of the catchments, thus allowing for agglomeration of similar catchments. Our results foster better understanding of the natural processes in the river basin, which definitely would help in better management of the environment and its relationship with huge number of people living there and depend on it. These results show that the regression tree methods based on CART algorithm can be used as effective tool for classification of catchments.

Hydromorphologically-driven variability of thermal and oxygen conditions at the block ramp hydraulic structure: The Porebianka River, Polish Carpathians.

Growing anthropopressure in mountain streams aimed at limiting erosion and flood protection often caused adverse effects on the natural environment. In recent years, great attention has been paid to the restoration and conservation of natural habitats in mountain streams using environmentally friendly solutions such as the Block Ramp (BR) Hydraulic Structures. In this study we investigated the factors responsible for spatial variability in thermal and oxygen conditions at the single BR structure in the growing season, and the relation between water temperature and dissolved oxygen (DO) concentration. This has been done by measurements of hydraulic characteristics along with physicochemical properties of water, such as water temperature and DO concentration, at two different discharges. The redundancy analysis has been applied in order to describe the relationships among hydraulic parameters and physicochemical variables, and extract potential sources of water temperature and DO variability within the BR hydraulic structure. Results have shown that DO and water temperature distributions within the BR hydraulic structure depend on discharge conditions and are associated with the submergence of the block ramp. The highest heterogeneity in hydraulic, DO and water temperature conditions occurs at low flow and is associated with the presence of crevices between protruding cobbles at the block ramp. The lowest variability, in turn, occurs at high discharge, when the block ramp is completely submerged. The results indicated that thermal and oxygen conditions within the BR hydraulic structure are independent of hydraulic parameters at low flow. Moreover, the relation between DO concentration and water temperature is positive at low flow indicating potential impact of biological processes. On the contrary, at high discharge both, the DO concentrations and water temperature within the BR structure, depend on bed shear velocity and maximum Reynolds number.

Link between hydric potential and predictability of maximum flow for selected catchments in Western Carpathians.

This study aimed to determine the link between a hydric potential of catchments (LHP) and the predictability (P) of maximum flow of selected rivers in southern Poland (within the Upper Vistula basin) and Slovakia. The LHP method refers to the ability of ecosystems to slow down runoff and retain water. The LHP method is focused on the analysis of the following indicators, shaping the geosphere at the catchment scale: hydrogeological conditions, soil conditions, meteorological conditions, geomorphological conditions, and land use. The predictability of river flows, calculated as one of the Colwell's indices, represents a measure of confidence with regard to the state of a flood event at a given point. To determine links between the LHP and P, a cluster analysis was used with the Ward method of agglomeration. The mean LHP varied between 1.2 for the Skawa River and 20.1 for the Vistula River. Only the Vistula River has very high LHP. The rest of the investigated rivers had medium and low values of LHP. The mean predictability of maximum flows for all rivers was relatively high (0.54), with the highest value obtained for the Wislok River (0.69) and the lowest one for the Bialka River (0.40). Cluster analysis showed that the studied catchments may be aggregated into four homogeneity clusters: first - catchments with high P and limited LHP, second - catchments with mean P and low LHP, third - with low P and average LHP and fourth - with very high P and medium and excellent LHP. The results are important for the management of catchments, especially for planning of any land use changes and investment projects related to water retention.

Island development in a mountain river subjected to passive restoration: The Raba River, Polish Carpathians.

In the twentieth century the heavily channelized Raba River incised deeply in its mountain course. Abandonment of channelization structures in a 2.3-km-long reach within a forested corridor was followed by considerable channel widening during floods of 30- and 35-year recurrence interval, re-establishment of a multi-thread channel pattern and island development. Morphological and botanical surveys were conducted annually between 2011 and 2017 to determine the processes and patterns governing development of islands and their floristic complexity. Hydraulic conditions promoting establishment and persistence of islands were determined with one-dimensional hydraulic modelling of flood flows for 8 unmanaged river cross-sections with islands and 8 cross-sections in the adjacent channelized reaches. Average age, number of islands and their average and total area in the reach markedly increased over the study period. However, the increase was not steady but moderated by island erosion by flood flows, island establishment shortly after major floods and island coalescence in the years without such floods. Hydraulic modelling indicated that river cross-sections with islands are typified by significantly lower values of mean water depth, flow velocity, unit stream power and bed shear stress at flood flows than cross-sections in the adjacent, channelized reaches. Such conditions promote deposition of living driftwood on channel bars, initiating island development, and reduce the probability of erosion of existing islands. The total number of plant species on islands varied highly and either exceeded or was similar to that recorded on riparian forest plots in particular years. This study indicates that (i) island re-establishment in the river was initiated by substantial channel widening, (ii) variation in flood magnitudes exerts a considerable influence on the trajectory of island development, and (iii) the contribution of islands to the overall species richness of plant communities in the river corridor at early stages of island re-establishment may be highly varied.

Possibilities of fish passage through the block ramp: Model-based estimation of permeability.

Block ramps offer an opportunity to combine hydrotechnical structures with fish passages. The primary study objective was to evaluate the effectiveness of a block ramp for upstream fish movement in a mountain stream. Geodetic measurements of the bottom surface and water level were taken for three cross-sections. The description of the geometric and hydrodynamic parameters of the block ramp was supplemented with information on the width and length of crevices between boulders. Measurements of the geometric and hydrodynamic parameters of the block ramp were performed at 76 measurement sites, at three different types of discharge. Ichthyological data were collected in the analyzed stream. Measurements covered among others total length, width, and height of caught fish. Salmonid, cottid, balitorid, and cyprinid fish were studied. The determination of the main effects of the geometric and hydrodynamic parameters of the block ramp on the possibilities of use by target fish species employed generalized linear models (GLMs). The study shows that the block ramp cannot provide longitudinal connectivity and migration of fish occurring in the mountain stream. According to estimates, the block ramp did not meet the permeability expectations. The reason for low usefulness of the ramp for fish is particularly excessively strong water current. The stream concentration constituted an unsurmountable velocity barrier for fish moving upstream for each of the analyzed discharges. The developed model suggests that some crevices in the side zones of the ramp could be parts of the migration corridor, but only for small and medium-sized fish. At medium and high water stages, movement of fish in crevices was difficult due to fast water current, and at low and very low discharges, some crevices lost their permeability, and could become ecological traps for fish. The necessity of estimation of ramp permeability during pre-construction phase was emphasized.

Ecological state of a mountain river before and after a large flood: Implications for river status assessment.

Assessment of the ecological status of rivers is key to monitoring the achievement of the environmental goal of the EU Water Framework Directive and the success of restoration projects. In summer of 2009 and 2010, repeated assessments of physical habitat conditions and of fish and benthic invertebrate communities were performed at low-flow conditions in 10 unmanaged and 10 channelized cross-sections of the Biala River, Polish Carpathians. Between the two surveys, an 80-year flood occurred, significantly affecting habitat characteristics and river communities. In unmanaged cross-sections, active channel width increased, whereas the degree of cross-sectional variation of flow velocity decreased. In channelized cross-sections, the increase in active channel width and the cross-sectional variation of flow velocity was accompanied by a decrease in bed-material grain size. Before the flood, the unmanaged cross-sections hosted 2.3 times more benthic invertebrate taxa than the channelized ones, whereas after the flood, the number of taxa they supported was so reduced that the taxonomic richness of benthic invertebrate assemblages in both cross-section types became similar. In comparison to pre-flood conditions, the abundance of fish juveniles (YOY) in unmanaged cross-sections was reduced nearly by half; before the flood they hosted 5 times more juvenile individuals than channelized cross-sections and only twice as many after the flood. Finally, a differing assessment of flood impact on the ecological river quality was obtained with the invertebrate-based BMWP-PL index and the European Fish Index, with the former indicating a significant reduction of the quality in unmanaged cross-sections and the latter pointing to no such change. The results indicate that assessments performed before or after a major flood may yield significantly different results for the quality of abiotic and biotic elements of the river ecosystem. Final assessment should thus be based on repeated surveys to balance the effect of extreme hydrological events.

Plant basket hydraulic structures (PBHS) as a new river restoration measure.

River restoration has become increasingly attractive worldwide as it provides considerable benefits to the environment as well as to the economy. This study focuses on changes of hydromorphological conditions in a small lowland river recorded during an experiment carried out in the Flinta River, central Poland. The proposed solution was a pilot project of the construction of vegetative sediment traps (plant basket hydraulic structures - PBHS). A set of three PBSH was installed in the riverbed in one row and a range of hydraulic parameters were recorded over a period of three years (six measurement sessions). Changes of sediment grain size were analysed, and the amount and size of plant debris in the plant barriers were recorded. Plant debris accumulation influencing flow hydrodynamics was detected as a result of the installation of vegetative sediment traps. Moreover, various hydromorphological processes in the river were initiated. Additional simulations based on the detected processes showed that the proposed plant basket hydraulic structures can improve the hydromorphological status of the river.

Comprehensive approach to the reduction of river flood risk: Case study of the Upper Vistula Basin.

The paper examines options for river flood risk reduction in the Upper Vistula Basin located partly in the Carpathian Mountains in Poland. Projections of high-flow indices for the periods 2021-2050 and 2071-2100 generally indicate small future increases, although the projected flow changes vary highly both across the study basin as well as among climate models. An overview of twentieth-century catchment and channel changes indicates that some of them decreased and others increased the rapidity of runoff but they largely reduced availability of sediment for fluvial transport, hence inducing bed incision and bank erosion that create risk to roads and bridges. Traditional methods of flood protection in the basin encompassed large structural defences such as river channelization and flood embankments. These have limited floodwater retention within floodplains and accelerated flood runoff, shifting flood hazard downstream rather than reducing it. A range of alternative approaches to reducing future flood risk are thus proposed and examples of their application in southern Poland are described. These approaches include river restoration measures aimed to reduce erosional potential of flood flows and increase channel and floodplain retention of floodwater, as well as grassroots initiatives promoting preparedness for flooding at the community level. There is an increasing need to change the existing paradigm that flood-control measures should be based on fast evacuation of floodwater that, in turn, was associated with a significant reduction in floodwater retention on the valley floors. Alternative approaches discussed in this paper extend the roster of flood risk reduction strategies and contribute to a gradual paradigm change.