Fluvial Forms Research Articles

Geomorphological analysis of the Antinaco‐Los Colorados valley, La Rioja province, Argentina

AbstractThe Antinaco‐Los Colorados valley (ALCV) is a tectonic depression located in the centre‐north of the province of La Rioja (Argentina), limited to both the east and west by mountain ranges, in the broken foreland region. Geomorphological research on environmental dynamics is important for both building a reference framework for further studies and for the development of the socio‐economic activities in the area. This study presents the main geomorphological features of the tectonic depression at the regional scale in order to identify the primary factors involved in its evolution and the landforms it contains. The ALCV is asymmetric, and it is filled by up to 1600 m of sediments along the western margin. Using literature, images, digital elevation models of the study area and field work, different morphologies were identified in the valley, mostly linked to Quaternary climatic and tectonic changes. These morphologies were grouped into three main morphogenetic units that characterize this landscape: the relict piedmont levels, the current piedmont and the fluvial‐aeolian plain. The identification of fluvial forms suggests that fluvial systems have been important during the evolution of the landscape. Aeolian accumulation features, currently mostly vegetated, were likely formed under drier climatic conditions than those at present and probably related to the last ice age or even more recent times. Successive reactivations of the overall system are not only tectonic, as evidenced by the structural lineaments that affect relict piedmont levels and the fluvial‐aeolian plain, but also climatic. Thus, the identified landforms suggest that climatic and tectonic variables account for the variations in the environment of the ALCV, affecting the reaccommodation of the exogenous geomorphological processes and the modelling of the relief.

Reclaiming Energy Flows: Energy GeoHumanities and the Socio-Ecologies of Rivers in Latin American Hydro-Modernities

This article explores fluvial forms of art and activism to reclaim new meanings of energy at a time when questions about the energy transition are central in geography studies and global environmental discourses. Departing from Serpent River Book by Carolina Caycedo, we propose affective, embodied, and creative entanglements to understand energy flows in river ecologies in Latin America for an exploration of energy geohumanities. We then discuss the methodology of this energy geohumanities project in our engagements with Caycedo’s art, reflecting on our sedimentary writing and thinking process enacted throughout the article. By centering this article on what energies art conjures and releases in affective and political terms, we explore the meanings of doing energy geohumanities in the deployment of a poetics of embodied tensions between flow and containment and between aerial and immersive views that challenge the dichotomies of subject/object, nature/culture and geo/human. Through unfolding a “sedimentary blog writing” method based on geo-mimicry, we hope to make a case for how entangled thinking and writing offer a novel approach to examining the multiple meanings of energy beyond electricity in the extractive zones of hydro-modernity.

Longitudinal Profiles and Geomorphic Indices Analysis on Tectonic Evidence of Fluvial Form, Process and Landform Deformation of Doodhganga, SW Kashmir Valley, NW Himalayas

Longitudinal Profiles and Geomorphic Indices Analysis on Tectonic Evidence of Fluvial Form, Process and Landform Deformation of Doodhganga, SW Kashmir Valley, NW Himalayas

Why Consider Geomorphology in River Rehabilitation?

River rehabilitation and ecological engineering are becoming critical issues for improving river status when ecological habitats and connectivity have been altered by human pressures. Amongst the range of existing rehabilitation options, some specifically focus on rebuilding fluvial forms and improving physical processes. The aim of this contribution is to illustrate how geomorphological expertise and process-based thinking contribute to river rehabilitation success. This semantic contribution is intended to feed the rehabilitation debate, particularly concerning the design of actions and the proposed references for monitoring target reaches and evaluating rehabilitation effects empirically. This article is also based on lessons learned from practical cases, mainly in gravel-bed rivers. Geomorphic understanding is needed at a local level to achieve an adequate diagnosis of river functioning, estimate human impacts and potential remnant river responsiveness, and to assess the gains and risks from rehabilitation, as well as to appraise success or failure through several pre- and post-project assessment strategies. Geomorphological studies can also be upscaled in a top-down manner (from high-order controls to small-scale processes, understanding detailed processes in their regional or basin-wide context), providing large-scale information at the regional, national, or even global level, information that can be used to diagnose the health of riverscapes in relation to local site-specific contexts. As such, geomorphological studies support strategic planning and prioritization of rehabilitation works according to specific contexts and river responsiveness, so as to move from opportunistic to objective-driven strategies.

A quantitative depositional model of a large distributive fluvial system (Megafan) with terminal aeolian interaction: The Upper Jurassic Guará DFS in southwestern Gondwana

ABSTRACT Recent studies have shown that distributive fluvial systems are the dominant fluvial forms in modern continental sedimentary basins, thus composing a large part of the stratigraphic record. This study provides a basin-scale architectural analysis of the Guará Formation, from the Upper Jurassic record of southwestern Gondwana, and attempts to compare the formation's depositional model to those developed for distributive fluvial system (DFS) successions. This time interval is significant because it was a period of intense tectonic activity related to the Paraná–Etendeka plume and the Gondwana breakup. Quantitative analyses were performed on stratigraphic sections at 17 locations (exposing a total of 720 m of stratigraphy) located in southern Brazil and northern Uruguay, from a larger dataset of 64 locations (comprising a total of 1070 m of stratigraphy). Four facies associations were identified: perennial fluvial channel fills, ephemeral fluvial channel fills, floodplain deposits, and aeolian deposits, indicating a dryland climate. Spatial trends were analyzed along a downstream-oriented transect (NNE–SSW) across the system. Grain size, channel-body thickness, number of stories, and bar thickness decrease downstream, indicating a reduction in channel depth, flow capacity, and channelization of the fluvial system, interpreted to be associated with downstream-increasing bifurcation, infiltration, and evapotranspiration. Based on spatial trends and distribution of facies associations, the deposits are interpreted to have been accumulated from a large DFS which can be divided into four zones, from proximal to distal: Zone 1, dominated by perennial fluvial channels; Zone 2, a mixture of perennial and ephemeral channels; Zones 3 and 4, deposits situated externally of the fluvial channel belts dominated by aeolian and floodplain deposits prevailing in each zone, respectively. The Guará Formation likely records the stratigraphic signature of the largest distributive fluvial systems reconstructed from both modern and ancient datasets, and one of the first where fluvio–aeolian interaction is quantified. The Guará Formation DFS model presented herein is key to understanding paleoenvironmental, paleoclimatic, and geotectonic changes related to Gondwanan fragmentation.

Bank re‐erosion action to promote sediment supply and channel diversification: Feedback from a restoration test on the Rhine

AbstractRiver regulation alters hydrological and sediment regimes and consequently affects habitat complexity and dynamics, biodiversity and ecosystem services. Although channel bank erosion is a key geomorphological process supplying alluvial channels with coarse sediments and diversifying aquatic and riparian habitats, banks have often been stabilized to limit erosion risk to human activities and facilities. The objective of this paper is to assess the effects, and their sustainability, of bank protection removal on a 300‐m long reach of the Old Rhine (France/Germany) to promote sediment supply, channel diversification and a rehabilitation of fluvial morpho‐sedimentary processes. This action was combined with the construction of two island groynes to locally increase bank erosion processes. Yearly detailed monitoring was implemented over 6 years, including classical bathymetric surveys, airborne topo‐bathymetric and terrestrial LiDAR, and bed grain‐size and bedload tracking. Following a Q15 flood, the restoration induced a weak sediment supply. The restoration diversified habitats due to the implementation of the two island groynes, inducing bank scouring and the creation of new macroforms, as well as local bed grain‐size diversification and fining. The cross‐sectional diversity of the restored water channel was close to the regularization engineering phase. Channel bedform diversification persisted 6 years due to the persistence of the two island groynes. The action induced the rehabilitation of fluvial forms, in a static manner, rather than the rehabilitation of fluvial morpho‐sedimentary processes, which raises questions about the sustainability of the benefits of such management actions in terms of fluvial functionality and naturality.

Ecological Impacts of Altered Stream Hydrogeomorphic Characteristics Extend Beyond the Channel Boundary: Evidence From Urban Streams of Columbus, OH, United States

Urbanization in stream catchments can have strong effects on stream channel hydrogeomorphic features including channel dimensions, channel-floodplain connectivity, and flood regime. However, the consequences of hydrogeomorphic alterations on aquatic-terrestrial subsidy dynamics are largely unexplored. We examined the associations among hydrogeomorphic characteristics, emergent aquatic insect assemblages, and the density and trophic dynamics of riparian spiders of the family Tetragnathidae at 23 small urban stream reaches in the Columbus, OH (United States) Metropolitan Area. Naturally abundant stable isotopes of 13C and 15N were used to quantify the relative contribution of aquatically derived energy (i.e., nutritional pathways deriving from algae) to tetragnathid spiders and their trophic position. Bankfull discharge was negatively related to both emergence rate and family richness. On average, tetragnathid spiders relied on aquatically derived energy for 36% of their nutrition, with the greatest reliance found for spiders next to channels with wider flood-prone widths and proportionally fewer emergent insects of the family Chironomidae. Mean emergent aquatic insect reliance on aquatically derived energy was 32% and explained 44% of the variation in tetragnathid aquatically derived energy. A positive relationship between δ13C of tetragnathid spiders and emergent insects provides additional evidence of tetragnathid reliance on emergent insects. Mean tetragnathid trophic position was 2.85 and was positively associated with channel sinuosity and negatively associated with aquatic insect emergence rate. Sinuosity was also positively related to aquatically derived energy of emergent aquatic insects; as well as emergent insect family richness; % Ephemeroptera, Plecoptera, and Trichoptera (EPT); and aquatic insect emergence rate; implicating instream habitat-mediated shifts in emergent aquatic insect communities as an indirect mechanistic link between hydrogeomorphic processes and spiders. Our findings underscore that the impacts of stream hydrogeomorphic alterations can cascade into terrestrial food webs. These results suggest that monitoring and restoration of fluvial geomorphic form and function (e.g., sinuosity, slope, and hydrology) confer benefits to both aquatic and terrestrial riparian ecosystems in urban catchments.

Analysis on the change of runoff curve number influence to surface flow debit using ALOS AVNIR-2 data imagery

One part of the hydrologic cycle which has a major influence in increasing the amount of river flow discharge is surface runoff. The higher surface runoff discharge, causing the possibility of surface flooding, therefore required an empirical model that can calculate the amount of surface runoff so as to produce updated data and quickly change according to their needs. One of the empirical methods that can be used to calculate the amount of surface runoff is by using the curve number method. This research is done by utilizing remote sensing image, that is, ALOS AVNIR-2. Data extraction from ALOS imagery includes land cover information using multispectral classification analysis, slope inclination information through visual interpretation, and land use interpretation. The runoff that occurred in Banjarnegara Regency tends to be high, that is, 61.24 percent of the total area of the research area. Large runoff with very high/extreme class spread on the form of hilly land to the old volcano complex at the study site. The runoff in the medium to low class only covers 3.56 percent of the total area and is distributed on the fluvial form with the flat-to-flat slopes. The result of analysis of runoff data is obtained from slope analysis and type of land use in the research location. Increasingly steep slope with little vegetation-land use, then the greater the runoff that occurs. Finally, the research result could be implemented into higher student class activity, especially in remote sensing classes, GIS, cloud computing, and big data analysis. By this process, the students will be improved their skills in analyzing imagery data as well as create new information derived from the remote sensing data.

Why do large rivers tend to form multichannel? A field study in the Upper Paraná River

Anastomosed rivers include a diverse group of fluvial forms with multiple and interconnected alluvial channels. They occur in a wide range of climates and reliefs and constitute the typical pattern of the mega rivers (Qm> 17,000 m3s-1). Several authors have assumed that the development of an anabranching formation is the mechanism by which a channel maintains its maximum efficiency. However, this has only been tested by mathematical studies. In this study, we confirm this theory in a 58-km anabranching reach of the Upper Paraná River, through a hydraulic and bathymetric survey of 14 cross-sections. We conclude that where the slope can'tincrease, the channel reduces its w:d ratio, thereby maintaining its efficiency in the wider sections, according to the specific stream power equation (ω=ρgQs/w). The channel width and alluvial plain width are controlled by allochthonous factors (tectonic lineaments and bank composition). Although the nodal sections have the greatestefficiency, we confirmed that flow efficiency is maintained at a constant level of bedload transport and specific stream power along the anabranching reach.

Jokiuoman kartoitus ja virtausolosuhteiden mallinnus tukena perkauksen suunnittelussa: esimerkkinä Eurajoki

Dredging has a significant effect on sediment transportation, water quality and flow conditions in a river channel. However, often the effects of dredging are not studied carefully in advance. One reason for this is the lack of suitable study approach. Studies on river dynamics require high quality geometric models of riverbed, banks and floodplain. Accurate terrain and bathymetric data are also crucial components of reliable hydraulic modelling. In this study, we created an approach to model the presumable impacts of dredging. We modelled high discharges and annual flooding magnitudes in Eurajoki River, SW Finland in its current form and after dredging. As the low-sloped channel is heavily vegetated, the aim of the dredging is to improve flow conditions by removing sediment and vegetation within a reach of 8 km. First, we created a geometric model of the riverine environment by combining riverbank topography from national Airborne Laser Scanning (ALS) data by the Finnish National Land Survey and bathymetry, gathered with an Acoustic Doppler Current Profiler (ADCP). The ADCP was attached to a kayak to enable access to shallow areas as well. This way, we were able to model the geometry of the fluvial forms within a few centimetres’ accuracy. Next, we modified the model of the river geometry using GIS software according to the dredging plan. Finally, we used a 2D Computational Fluid Dynamics to model the current and after dredging flow conditions during various flow events. We analysed the effects on dredging on the flood magnitudes and flow conditions based on the models and compared these to the present situation. These models offer improvements on river management and observing the effects on dredging.

RELYEF VƏ ONUN GENETİK TİPLƏRİNİN KÜR-ARAZ OVALIĞI AQROKOMPLEKSLƏRİNİN FORMALAŞMASINA TƏSİRİ

The article discusses one of the factors influencing the formation of agro-complexes of the Kur-Araz lowland - relief and its genetic types, A brief description of each of the genetic types is given. Eco-geographical assessment of these factors is also discussed. Key words: alluvial plains, accumulative plains, inflow cones, eol relief forms, fluvial relief forms, river terraces, abrasion and abrasion-accumulative relief forms, arid denudation relief forms

Geomorphic controls on the diversity and patterns of fluvial forms along longitudinal profiles

A mix of catchment-scale controls operate to determine geomorphic river diversity in a catchment. These are contextualised here as imposed and flux controls. Imposed controls do not adjust over geomorphic timeframes and produce the environmental setting in which a river functions. Flux controls are dynamic interactions between flow and sediment that heavily influence geomorphic river diversity. We measure and statistically analyse the network scale mix of imposed and flux controls occurring along longitudinal profiles of various shape. We use this to explain the diversity, pattern and sequence of river types at different positions in a catchment. Using the Richmond River catchment, New South Wales, Australia, as our case study we analyse the imposed controls of slope and valley bottom width and the flux controls of bed material size and gross stream power for five river types, ranging from confined continuous rivers in headwaters to laterally unconfined discontinuous rivers in lowland plains. We find that slope and gross stream power are strong, positively correlated controls on all river types, but act most strongly on rivers with continuous channels. In contrast, bed material size is a dominant control on rivers with discontinuous channels. Slope and gross stream power are also critical for determining the downstream pattern of river types along longitudinal profiles. However, the relationship between these controls is complex as not all rivers are influenced by these controls in the same way. Understanding the mix and patterns of controls operating along longitudinal profiles can be used to explain the variability and pattern of river types we see in the landscape.

Is Marine Survival for Puget Sound’s Wild Steelhead Really That Bad? A Nisqually River Case Study Evaluating Estimates of Productivity and Survival of Oncorhynchus mykiss

AbstractWe highlight the uncertainty that exists around estimating productivity and survival for one population of threatened steelhead Oncorhynchus mykiss (anadromous Rainbow Trout) with the goal of strengthening our understanding of the well‐documented poor marine survival of Puget Sound steelhead. We evaluated how sensitive estimates of productivity and survival were to the uncertainty associated with smolt trap enumerations, redd survey methodology, estimates of fish per redd, and estimates of smolt production by resident Rainbow Trout in order to clarify causes of poor steelhead survival in this area. We show that from 2004 to 2014, estimates of both freshwater productivity and marine survival were highly sensitive to estimates of fish per redd used to expand redd counts, as well as error around smolt abundance estimates. Regardless, uncertainty associated with these inputs did not explain the low survival and high productivity observed for Nisqually River steelhead relative to other populations. In addition, we identified progeny from anadromous mothers upstream of what was previously considered a barrier, and we also documented that a proportion of steelhead smolts (N = 4/43) originated from resident mothers (Rainbow Trout). While these results indicated an underestimation in the total number of steelhead redds counted each year and an overestimation of steelhead progeny enumerated at smolt traps, they had little impact on estimates of survival and productivity. Results from the current study support previous work reporting poor marine survival for populations of Puget Sound steelhead and highlight the sympatric relationship between resident and anadromous life histories of O. mykiss. Overall, our study supports a management strategy that protects both the anadromous and fluvial forms of O. mykiss, prioritizes habitat improvements that promote freshwater productivity, and increases research focused on identifying causes of poor marine survival.

Spatial validation of submerged fluvial topographic models by mesohabitat units

ABSTRACT Mapping the streambed morphology is crucial for understanding fluvial forms and processes, for advancing both our knowledge and best management practice of riverine systems. It is often done by wading streams but recently topobathymetric Light Detection and Ranging (LiDAR) and imagery captured from airborne platforms are becoming promising and effective surveying methodologies. The recent use of remotely piloted aerial systems (RPAS) combined with structure-from-motion (SfM) photogrammetric processing provides a novel, high-resolution approach to modelling fluvial morphology. Nevertheless, a complicating factor of such data acquisition in fluvial settings is linked to water bodies, whose presence introduces errors and distortions because of light reflection and refraction at the air–water interface. Although proof-of-concept research has shown it is possible to reduce the effects of refraction in certain settings (e.g., clear waters, unbroken surfaces), corresponding validation methods remain limited to point-based assessments of error, these being typically limited to accessible parts of the channel. Here, we provide the first high-resolution, spatially continuous validation of a stream reach bathymetry surveyed with SfM and corrected with an advanced refraction method. This method required only the camera co-ordinates and is available as open source, coded in C++. We used RPAS imagery from a regulated reach of the Palancia River, Spain, where a diversion structure fully dewatered the reach and let us obtain the entire streambed topography, which we used as spatially continuous control topography to compare the bathymetry surveyed from imagery during normal flow conditions. We compared this method with the small angle refraction correction (SARC), which has less data requirements, and analysed the error distribution across habitat types (i.e. pools and riffles). These results showed that our approach had smaller errors than SARC in both habitat types, especially in the riffle. By analysing the relationship between error and channel roughness obtained from our dry-bed model, we found that the greatest errors arise in the peripheral zones of the water surface and in its areas where streambed roughness generates more turbulence. Quantitative validation confirmed the reliability of our method as a relatively low-cost tool for the modelling and management of geomorphology and habitat within small – to medium-sized streams.

The Late Quaternary Evolution of the Upper Reaches of Fluvial Systems in the Southern East European Plain

Networks of dry valleys (or balkas) and hollows in the upper reaches of fluvial basins in extraglacial areas in the Penultimate Glaciation (Marine Isotope Stage 6—MIS 6) regions of the East European Plain demonstrate clear incision/aggradation rhythms corresponding to global glacial/interglacial climate cycles. The first phase of each incision/aggradation rhythm began after the global glacial maximum and was characterized by a cool and humid climate, permafrost and sparse vegetation, when high surface runoff and active linear erosion formed a dense network of gullies. The second phase occurred at the glacial–interglacial transition and the subsequent interglacial period with its warm and humid climate and dense vegetation. This phase was distinguished by the partial filling of fluvial forms with slopewash deposits, the transformation of gullies into dry valleys (balkas) and the subsequent stabilization of fluvial forms marked by the formation of mature soils on the sides and bottoms of balkas. The third phase of the rapid accumulation of balkas developed during the cold and dry part of the next glacial epoch, resulting in the balkas becoming shallow hollows filled in with sediments. The last full incision/aggradation rhythm occurred in the late MIS 6 to mid-MIS 2. The erosion network formed during the late MIS 6 was almost completely filled by mid-MIS 2, and its manifestation in the modern topography is limited to a network of shallow hollows in the upper parts of the fluvial systems. The modern (incomplete) incision/aggradation rhythm began in the late MIS 2 and caused the formation of the modern erosion landscape in the upper reaches of fluvial systems. This rhythm is now in the stabilization phase, and the main accumulation phase of this rhythm is still far in the future.

Application of multi-criteria decision-making approach for ascertaining the avulsion potentiality of the Torsa River course

This work has been a scientific venture to analyse the avulsion potentiality in the course of the Torsa River flowing across the Himalayan Foreland Basin (HFB) in West Bengal, India. A total of nine parameters, based on theoretical propositions regarding their corresponding role in channel avulsion, were selected to calculate the Avulsion Potentiality Index (API). Since the weightage of the topographic and planimetric parameters vary correspondingly in the avulsion process, a supervised technique of assigning weightage to multiple criterias, the analytic hierarchy process (AHP) has been used in this study. The weightage-based compound scoring was conducted using the weighted linear combination model (WLC). API was calculated for the Torsa River considering the equal interval-based compartmentalization of the course as individual spatial units of analysis. It has been an approach where the palaeofluvial events, i.e. old avulsion history and associated fluvial expressions, have been integrated with the present fluvial forms, i.e. channel planform and floodplain topography, to predict the future possibilities. The prediction done using the model was found significant in the real world. 71% of the highly avulsion prone channel segments have experienced channel avulsion during the post-analysis period. The channel segments with high in-channel sedimentation rate and downstream segments of the confined stretches, both anthropogenic and structural, were found more susceptible to avulsion. On-field verification of the avulsion events has dished up the characteristic influences of both the floodplain topography and channel planform parameters on avulsion events in the Torsa River course.

Aerial Laser Scanning Data as a Source of Terrain Modeling in a Fluvial Environment: Biasing Factors of Terrain Height Accuracy.

Airborne light detection and ranging (LiDAR) scanning is a commonly used technology for representing the topographic terrain. As LiDAR point clouds include all surface features present in the terrain, one of the key elements for generating a digital terrain model (DTM) is the separation of the ground points. In this study, we intended to reveal the efficiency of different denoising approaches and an easy-to-use ground point classification technique in a floodplain with fluvial forms. We analyzed a point cloud from the perspective of the efficiency of noise reduction, parametrizing a ground point classifier (cloth simulation filter, CSF), interpolation methods and resolutions. Noise filtering resulted a wide range of point numbers in the models, and the number of points had moderate correlation with the mean accuracies (r = −0.65, p < 0.05), indicating that greater numbers of points had larger errors. The smallest differences belonged to the neighborhood-based noise filtering and the larger cloth size (5) and the smaller threshold value (0.2). The most accurate model was generated with the natural neighbor interpolation with the cloth size of 5 and the threshold of 0.2. These results can serve as a guide for researchers using point clouds when considering the steps of data preparation, classification, or interpolation in a flat terrain.

Effects of Transverse Groynes on Meso-Habitat Suitability for Native Fish Species on a Regulated By-Passed Large River: A Case Study along the Rhine River

River regulations ultimately degrade fluvial forms and morphodynamics and simplify riparian and aquatic habitats. For several decades, river restoration actions have been performed to recover geomorphic processes and diversify these habitats to enhance both river biodiversity and ecosystem services. The objective of this study is to provide quantitative feedback on the experimental restoration of a large regulated and by-passed river (the Upper Rhine downstream of the Kembs Dam, France/Germany). This restoration consisted of the construction of two transverse groynes and the removal of bank protection. A monitoring framework composed of topo-bathymetric surveys as well as flow velocity and grain size measurements was established to assess the channel morphodynamic responses and evaluate their effects on habitat suitability for five native fish species using habitat models. A riverscape approach was used to evaluate the landscape changes in terms of both the configuration and the composition, which cannot be considered with classic approaches (e.g., Weighted Usable Area). Our results show that the two transverse groynes and, to a lesser extent, bank erosion, which was locally enhanced by the two groynes, increased habitat diversity due to the creation of new macroforms (e.g., pools and mid-bars) and fining of the bed grain size. Using a riverscape approach, our findings highlight that the restoration improved eel and juvenile nase species due to slowing down of the current and the deposition of fine sediments downstream of both groynes. As a consequence, the restoration improved the habitat suitability of the studied reach for more fish species compared with the pre-restoration conditions. This study also demonstrates that the salmon habitats downstream of the restored reach were improved due to fining of the bed grain size. This finding highlights that, for restorations aimed at fish habitats, the grain size conditions must be taken into consideration along with the flow conditions. Furthermore, the implementation of groynes, while not a panacea in terms of functional restoration, can be a strategy for improving fish habitats on highly regulated rivers, but only when more functional and natural options are impossible due to major constraints.

Geomorphology as a Driver of Heavy Metal Accumulation Patterns in a Floodplain

The spatial complexity of floodplains is a function of several processes: hydrodynamics, flow direction, sediment transportation, and land use. Sediments can bind toxic elements, and as there are several pollution sources, the risk of heavy metal accumulation on the floodplains is high. We aimed to determine whether fluvial forms have a role in metal accumulations. Topsoil samples were taken from point bars and swales in the floodplain of the Tisza River, North-East Hungary. Soil properties and metal concentrations were determined, and correlation and hypothesis testing were applied. The results showed that fluvial forms are important drivers of horizontal metal patterns: there were significant differences (p &lt; 0.05) between point bars and swales regarding Fe, K, Mg, Mn, Cr, Cu, Ni, Pb, and Zn. Vertical distribution also differed significantly by fluvial forms: swales had higher metal concentrations in all layers. General Linear Models had different results for macro and micro elements: macro element concentrations were determined by the organic matter, while for micro elements the clay content and the forms were significant explanatory variables. These findings are important for land managers and farmers because heavy metal concentration has a direct impact on living organisms, and the risk of bioaccumulation can be high on floodplains.

Олешківські піски як ієрархічно побудована природна система

Оleshkivski Sands (Oleshia) are one of the morphosculptures on the Left bank of the lower part of Dnipro river, which is formed on alluvial and periglacial deposits. The article clearly identifies the location of these sands among other morphosculptures of the Left bank of the lower part of Dnipro. In view of the ambiguity, two regions of the Left Bank are considered separately – nearby arenian sandy-loamy geocomplexes with the presence of extremely specific sandy hilly-depressions geocomplexes and the territory of the hilly-lowland plain (Kardashynka lowland), which is located between the Dnipro delta and sands massives of the Kelegei arena. Oleshia consists of seven hilly-sanded arenas and six inter-arenial sanded flat plains. Accordingly, the area of Оleshkivski Sands is 219.9 thousand hectares, almost 80 % of which are sanded arenas. Arenas are represented here as hilly sandy plains and depressions. These sandy plains divided by sand types such as hilly (hillock, hillock-dune and hilly), hilly-ridge and flat-wavy, depressions – by flat-wavy, ridge-hollow, wavy-shallow depressions and ridge-shallow depressions. Such types of relief forms are represented by the following microforms of aeolian genesis: hillocks, hills, parabolic dunes, aeolian fields, deflation depressions and also by microforms of fluvial genesis: hilly-ridges, depressions among hilly sandy massifs, gally (redundans), inter-ridge depressions (inter-ridge hollows). On the surface of sandy massifs, especially in places where the sands are exposed, relief nanoforms are formed, which are represented by small riffles, nabkhas, blowing furrows, tafonies and also by aeolian trains, cut-off lobes, cliffs, cornices. This system of forms of relief of the Oleshkivski Sands testifies to the complex and various processes of their formation, but special attention should be paid at sand ridges, especially those with the parallel ridge-hollow spatial organization. They, for example, in the south of the Kinburn arena became the basis for the formation of the aeolian-hydrogen landscape that is unique for the territory of Ukraine. The author associates the creation of the Oleshіa ridge-hollow geocomplexes with the probable catastrophic floods (floodstreams). It is advisable to consider these ridges as a manifestation of giant ripples (diluvial dunes), which are often covered by deposits with different nature of formation. This is evidenced by the variety of typology of relief forms on the territory of the Oleshkivski arenas. Thalassogenic, suffusion-subsidence and anthropogenic factors also deserve special attention in characterizing of shaping the relief of the region. Key words: the Left bank of the Lower Dnipro, Оleshkivski Sands, hierarchy of relief forms, sandy arena, aeolian processes, fluvial forms.