Hydromorphological Conditions Research Articles

Bed Load Variability and Morphology of Gravel Bed Rivers Subject to Unsteady Flow: A Laboratory Investigation

AbstractMeasurement and estimation of bed load transport in gravel bed rivers are highly affected by its temporal fluctuations. Such variability is primarily driven by the flow regime but is also associated with a variety of inherent channel processes, such as flow turbulence, grain entrainment, and bed forms migration. These internal and external controls often act at comparable time scales, and are therefore difficult to disentangle, thus hindering the study of bed load variability under unsteady flow regime. In this paper, we report on laboratory experiments performed in a large, mobile bed flume where typical hydromorphological conditions of gravel bed rivers were reproduced. Data from a large number of replicated runs, including triangular and square‐wave hydrographs, were used to build a statistically sound description of sediment transport processes. We found that the inherent variability of bed load flux strongly depends on the sampling interval, and it is significantly higher in complex, wandering or braided channels. This variability can be filtered out by computing the mean response over the experimental replicates, which allows us to highlight two distinctive phenomena: (i) an overshooting (undershooting) response of the mean bed load flux to a sudden increase (decrease) of discharge, and (ii) a clockwise hysteresis in the sediment rating curve. We then provide an interpretation of these findings through a conceptual mathematical model, showing how both phenomena are associated with a lagging morphological adaptation to unsteady flow. Overall, this work provides basic information for evaluating, monitoring, and managing gravel transport in morphologically active rivers.

Investigation the stability of reservoir sediments in the lab and field

To investigate the erosion stability of reservoir sediments, two measuring strategies were applied. Next to in situ measurements, sediment cores were extracted and analysed in the laboratory. At several sampling points at a reservoir in Germany, the in situ device was used to determine the critical bed shear stresses at the sediment surface. At the same time, sediment cores were withdrawn at each site to perform depth-orientated investigations in the hydraulic laboratory. The objective of this study is to investigate the remobilisation potential of the deposited fine sediments and to compare different methods to determine the erosion threshold. Next to critical shear stresses and erosion rates, additional sedimentary and biological parameters were examined such as bulk densities, particle size distributions, TOC-contents and chlorophylla concentrations. The results show generally a very low erosion stability, especially at the sediment surface and in the upper sediment layers. Deeper sediment layers are characterised by consolidation effects and show a higher erosion resistance. High clay contents result in increased stability while high sand contents show a high remobilisation potential. No significant relation to the parameters TOC-content or chlorophylla concentration are identified. A comparison between the different applied techniques to determine the critical bed shear stresses reveals values in the same order of magnitude; however, some significant variations occur because of different hydromorphological conditions and the different limitations for each device.

Pesticides in agricultural headwater streams in southwestern Germany and effects on macroinvertebrate populations

Pesticides are a major burden for stream ecosystems in the central European cultivated landscape. The objective of the present study was to investigate the applicability of ecological indicator methods in relation to toxicity of pesticides under the specific hydro-morphological conditions in small water bodies. Thus, an association of toxicity evaluating methods with different ecological indicators was to be attempted. Based on three random samples taken within the 2016 vegetation period, 23 headwater areas in the Saarland were investigated to test for pesticides and their metabolites. The macroinvertebrate population was also surveyed in 16 of these streams. Evidence was found of 41 substances in total. Most dominant substances include atrazine, isoproturone, quinmerac and tebuconazol as well as metabolites of dimethenamid, chloridazon and metazachlor. At 9 of the 23 sampling points, over 10 plant protection products and metabolites were found. Only 17% of the water bodies investigated contained fewer than 5 substances. Around half of the bodies of water investigated show noticeably high concentrations of metabolites of plant protection products. Maximum concentrations exceeding environmental quality standards or the Health-oriented Guideline Values were measured for 13 substances at individual sampling points.Analysis of the biological data for only 4 of the water bodies investigated resulted in the Ecological Status Class (ESC) “good”. All others fell short of the quality target, although they were classified as “good” or “very good” according to the Saprobic index. SPEARpesticides as a measurement of the sensitivity of the biocoenosis to pesticides shows their influence in a few water bodies. Likewise, high toxic unit values have also been calculated, indicating the presence of toxic substances at relevant concentrations. However, an actual correlation between SPEARpesticides and toxic unit could not be derived. Clearly in these very headwater streams other habitat-determining hydromorphological factors overlay the toxic impact of pesticides.

Can beaver impact promote river renaturalization? The example of the Raba River, southern Poland

The European beaver (Castor fiber) was reintroduced in the Polish Carpathians in the 1980s after a few centuries of absence. It gradually colonized suitable habitats in the Raba River valley and elsewhere. The question arises as to whether beaver activity can play a role in the local improvement of hydromorphological conditions and spontaneous renaturalization of the Raba River channel. Field surveys were performed in morphodynamically and structurally homogeneous reaches of the river. Traces of beaver activity were identified and used to estimate the studied beaver population. Local beaver impact on the studied river channel was also determined. The Raba channel is trained along about 80% of its length and considerably incised. Traces of beavers activity were found in 16 out of 31 river reaches, mainly in the upper and lower river course. The study showed that relatively flat channel gradient, small maximum bed-material grain size, and high channel sinuosity favour beaver presence. The largest number of beaver habitats was identified in river reaches strongly altered by man and characterized by a uniform channel structure. Beaver impact on channel structure varies depending on differences of the river channel features in upper and lower reaches of the Raba River channel. In upper reaches, the impact of beaver activity (mostly dams) is reflected in increased lateral erosion, while slower water current reduces the tendency for bed degradation. In lower reaches, beaver impact is mostly limited to bank fragmentation (slides and burrows). Lateral erosion, accumulation of material at the toe of riverbanks, and wood debris accumulation all produce a local impact on river channel width. These beaver-initiated processes mostly alter artificially homogenized river reaches. Beavers may actually play a substantial role in future renaturalization of both upper and lower reaches of the Raba River.

Detailed fluvial-geomorphologic mapping of wadeable streams: a proposal of universal map symbology

ABSTRACTDetailed maps are important components of fluvial-geomorphological research, connecting several tools, namely field mapping of presented channel and floodplain forms and the assessment of fluvial processes and hydromorphological conditions of current river management. In this paper, we propose a universal map legend for the complex mapping of small stream channels in a detailed scale, which means including both the channel and adjacent floodplain segments. With the help of the symbology we are able to demonstrate both fluvial forms (i.e. individual features, grain size of bed sediments and fluvial deposits) and fluvial processes (i.e. contemporary trends in channels, character of lateral sediment inputs and flow characteristics) in a single map. In total, nearly 150 symbols were proposed and created as a combination of TrueType font and ArcGIS Style files. However, the principle can be used in various software. The work is accompanied by three map examples from the Nízký Jeseník Mts (the Stará Voda Stream) and the Moravskoslezské Beskydy Mts (the Lubina and Bystrý Streams).

Invasive Asian clam distribution pattern reveals minimal constraints to downstream dispersal and imperceptible ecological impacts

AbstractThe Asian clamCorbicula flumineais an invasive freshwater species that can cause adverse ecological and economic impacts. Information on its dispersal abilities, ecological preferences and impacts may contribute towards the improvement of management strategies, including those relating to regulatory demands such as the European Water Framework Directive (WFD).Both the above perspectives were addressed through inspection of environmental constraints toC. flumineadispersal and impacts in a semi‐natural drainage catchment (interconnected system of ditches). Forty sites were surveyed in 2014 to describe the species distribution and to characterize benthic macroinvertebrate communities, water column and sediment physico‐chemistry, as well as the hydromorphological conditions.Clams were unevenly distributed in the study area and artificial barriers (dikes) did not prevent downstream dispersal of juveniles. Large variation in clam density (0–3077 clams m−2) could not be explained by physico‐chemical or hydromorphological gradients. Although typical clam preference ranges reported in the literature were often exceeded, dense populations were nevertheless observed.Macroinvertebrate community structure suggested associations between the Asian clam and some functional feeding groups. However, the impacts of clams on macroinvertebrate assemblages and ecological quality were negligible, suggesting that contemporary methods designed to comply with the WFD bioassessment scheme may fail to detect important drivers of ecological change in freshwater ecosystems.This study demonstrated the reduced ecological impacts and broad ecological competence of the Asian clam, but also that its spread depends on human vectors. These findings highlight the need to rethink prediction tools supporting preventive measures against the introduction and spread of this invasive bivalve.

Identification of hydromorphological reference sites using the new REFCON method, with an application to rivers in the Czech Republic

This paper presents a new approach to establishing reference sites and determining hydromorphological characteristics for establishing type-specific hydromorphological reference conditions for rivers in the Czech Republic – the REFCON method – as well as its application. This method is based on hydromorphological river types. Using available maps and field surveys, it determines potential reference sites for establishing reference conditions, and subsequently, on the basis of an assessment of anthropogenic impacts using set criteria, it identifies stream reference sites. Reference sites and river types are validated using field survey data. This method also identifies characteristics of channel pattern, flow, riverbed structures, sediment, and variability of cross-sectional profiles used for establishing type-specific hydromorphological reference conditions.Reference conditions can be expressed using threshold values of individual characteristics (e.g., channel slope, entrenchment ratio, specific stream power); they can also be described qualitatively, that is, verbally (e.g., channel pattern, valley type). Nonetheless, reference conditions are always an expression of a set of characteristics or conditions that should be valid for a given river type.One of the expected results of applying this method is the creation of a reference site database for assessing hydromorphological status of streams. This database will serve for proposing stream restoration measures and also as a database of stream sections in need of protection from potential human impact.

Taxonomic and functional diversity of stream invertebrates along an environmental stress gradient

Anthropogenic stress has been identified as main driver of freshwater biodiversity loss. Adverse effects on the biodiversity of freshwater organisms, such as macroinvertebrates, may propagate to associated ecosystem functions, such as organic matter breakdown (OMB). In this context, the functional diversity (FD) of communities has been suggested to be a more suitable predictor of changes in ecosystem functions than taxonomic diversity (TD). We investigated the response of TD and FD of invertebrate communities to an environmental stress gradient and the relation of both metrics to the rate of organic matter breakdown. For this, we sampled macroinvertebrates and determined OMB using leaf bags along an environmental stress gradient (i.e. changes in physicochemical and hydromorphological conditions) in 29 low-order streams. Taxonomic richness decreased with increasing environmental stress (r=−0.55) but was not related to OMB. Conversely, the Simpson diversity of communities was not associated with the gradient but correlated moderately (r=0.41) with OMB. Of three functional diversity indices (functional richness, evenness and divergence), only functional richness correlated moderately with the stress gradient (r=−0.41) and any of the indices correlated with OMB. Nevertheless, functional metrics such as specific trait modalities and the total abundance of the dominant shredders correlated higher (r=0.46 and 0.48) with OMB than the TD indices. Given a relatively small species pool in our study and methodical constraints such as the limited resolution of autecological information, the FD might perform better in other contexts and if focusing on response and effect traits for the stressor and ecosystem function under scrutiny, respectively.

Assessment of river hydromorphological quality for restoration purposes: an example of the application of RHQ method to a Polish Carpathian river

Planning and implementation of effective restoration projects require appropriate assessment of a river’s hydromorphological status. Two European standards on hydromorphological assessment of rivers and hydromorphological assessment methods used in Poland are reviewed in the context of their applicability for river restoration purposes. River Hydromorphological Quality assessment method is presented with a case study of the Biała River, Polish Carpathians, where this assessment was used as basis for a restoration project aimed to establish an erodible river corridor. The results of the assessment revealed significant differences in hydromorphological quality between unmanaged and channelized river cross-sections, indicating channel regulation as a major cause of the hydromorphological degradation of the Biała and confirming the choice of the erodible river corridor as an appropriate method of its restoration. The assessment indicated hydromorphological features of the river that were severely modified within the channelized reaches and which are likely to improve the most with the removal of bank protection and allowing free channel migration.

Air-water CO2 and CH4 fluxes along a river-reservoir continuum: Case study in the Pengxi River, a tributary of the Yangtze River in the Three Gorges Reservoir, China.

Water surface greenhouse gas (GHG) emissions in freshwater reservoirs are closely related to limnological processes in the water column. Affected by both reservoir operation and seasonal changes, variations in the hydro-morphological conditions in the river-reservoir continuum will create distinctive patterns in water surface GHG emissions. A one-year field survey was carried out in the Pengxi River-reservoir continuum, a part of the Three Gorges Reservoir (TGR) immediately after the TGR reached its maximum water level. The annual average water surface CO2 and CH4 emissions at the riverine background sampling sites were 6.23±0.93 and 0.025±0.006mmolh-1m-2, respectively. The CO2 emissions were higher than those in the downstream reservoirs. The development of phytoplankton controlled the downstream decrease in water surface CO2 emissions. The presence of thermal stratification in the permanent backwater area supported extensive phytoplankton blooms, resulting in a carbon sink during several months of the year. The CH4 emissions were mainly impacted by water temperature and dissolved organic carbon. The greatest water surface CH4 emission was detected in the fluctuating backwater area, likely due to a shallower water column and abundant organic matter. The Pengxi River backwater area did not show significant increase in water surface GHG emissions reported in tropical reservoirs. In evaluating the net GHG emissions by the impoundment of TGR, the net change in the carbon budget and the contribution of nitrogen and phosphorus should be taken into consideration in this eutrophic river-reservoir continuum.

Characterising physical habitats and fluvial hydromorphology: A new system for the survey and classification of river geomorphic units

Geomorphic units are the elementary spatial physical features of the river mosaic at the reach scale that are nested within the overall hydromorphological structure of a river and its catchment. Geomorphic units also constitute the template of physical habitats for the biota. The assessment of river hydromorphological conditions is required by the European Water Framework Directive 2000/60 (WFD) for the classification and monitoring of water bodies and is useful for establishing links between their physical and biological conditions. The spatial scale of geomorphic units, incorporating their component elements and hydraulic patches, is the most appropriate to assess these links. Given the weakness of existing methods for the characterisation and assessment of geomorphic units and physical habitats (e.g., lack of a well-defined spatiotemporal framework, terminology issues, etc.), a new system for the survey and characterisation of river geomorphic units is needed that fits within a geomorphologically meaningful framework.This paper presents a system for the survey and classification of geomorphic units (GUS, geomorphic units survey and classification system) aimed at characterising physical habitats and stream morphology. The method is embedded into a multiscale, hierarchical framework for the analysis of river hydromorphological conditions. Three scales of geomorphic units are considered (i.e., macro-units, units, sub-units), organised within two spatial domains (i.e., bankfull channel and floodplain). Different levels of characterisation can be applied, depending on the aims of the survey: broad, basic, and detailed level. At each level, different, complementary information is collected. The method is applied by combining remote sensing analysis and field survey, according to the spatial scale and the level of description required. The method is applicable to most of fluvial conditions, and has been designed to be flexible and adaptable according to the objectives (e.g., reach characterisation, assessment, monitoring) and available data (e.g., image resolution). The method supports integrated hydromorphological assessment at the reach scale (e.g., the Morphological Quality Index, MQI) and therefore contributes to better establishing links between hydromorphological conditions at the reach scale, characteristic geomorphic units, and related biological conditions.

Diversification of the hydromorphological state and the habitat quality of streams in the Negev Desert (Israel)

The hydromorphological state and habitat quality of the selected streams in the Negev Desert was taken under consideration in the paper. Field studies were conducted in September 2014 on selected 500 m sections of streams (Nahal Be’er Sheva, Nahal Hebron) characterized by noticeable anthropopressure as well as on streams (Nahal Sansana, Nahal Yatir, Nahal Hatira) without visible human pressure. The survey of the hydromorphological state of selected streams was carried out using a British method, the River Habitat Survey (RHS). The hydromorphological state and habitat quality of the tested streams, based on the habitat naturalness indicator (HQA), as well as the habitat modification indicator (HMS), places the analysed streams of weak anthropopressure in class III—moderate (Nahal Yatir, Nahal Hatira) and IV—poor (Nahal Sansana). Bad hydromorphological state (class V) is the characteristic of the Nahal Hebron and Nahal Be’er Sheva streams with significant human pressure. However, it is important to verify RHS method and the classification of a hydromorphological state, especially the HQA index, and adapt them to the reference conditions in arid and semi-arid areas.

An environmental assessment of water replenishment to a floodplain lake

There are numerous wetland rehabilitation projects worldwide, but their efficiency is seldom assessed comprehensively. Oxbow lakes are wetlands of particular sensitivity. Within a large-scale floodplain rehabilitation project in Hungary, the Old Drava Programme, water replenishment was first carried out for the Cún-Szaporca oxbow lakes, a key area in the project. To assess its sustainability, the entire hydrological system has been monitored. From the data of hydrological monitoring (infiltration, soil moisture, groundwater/lakewater interaction) it is claimed that water replenishment involves significant losses through seepage (4.1 and 1.46 mm d−1) and evaporation (3.01 and 1.44 mm d−1) in the studied pre-intervention and replenishment periods, resp. Infiltration alone is insufficient to replenish groundwater and raise oxbow lake levels. In the critical summer half-year evaporation is intensive in the neighbouring agricultural fields. Groundwater table dynamics are controlled by hyporheic and groundwater flow. Major impact on the water balance of the oxbow lakes is exerted by the regime of the Drava River. A deepened lakebed is recommended to ensure more effective water retention in the oxbow lake. From the local study conclusions are drawn for the feasibility of rehabilitation at floodplain scale and in areas with similar hydromorphological conditions.

Water quality related macroinvertebrate community responses to environmental gradients in the Portoviejo River (Ecuador)

The Portoviejo River, located in the central western part of Ecuador, has been heavily impacted by damming, intensive agriculture and untreated wastewater discharge. Unfortunately, detailed information on the water quality and the ecological status of the Portoviejo River is not available, inhibiting decision-making and the development of water management plans. Therefore, the aims of this study were (1) to assess the ecological water quality, (2) to investigate the point along the environmental gradient where the most significant change in macroinvertebrate community occurs and (3) to find potential macroinvertebrate taxa that significantly change in abundance and frequency of occurrence along the Portoviejo River. To this end, macroinvertebrate and physico-chemical data were collected and hydro-morphological conditions were recorded at 31 locations during the dry season of 2015. The results showed that the ecological water quality of the sampling sites ranged from good to bad. In addition, the Threshold Indicator Taxa ANalysis was used to examine changes in macroinvertebrate communities and revealed significant community change points for sensitive taxa declining at a conductivity value of 930 (μS.cm−1 ) and nitrate-nitrogen concentrations of 0.6 mg.L−1 . In addition, the thresholds estimated for tolerant taxa were set at a conductivity value of 1430 μS.cm−1 and nitrate-nitrogen concentration of 2.3 mg.L. Atyidae, Corbiculidae, Thiaridae, Acari, Baetidae and Leptohyphidae can be considered indicator taxa, showing shifts in the community. This study suggests that values of conductivity and nitrate-nitrogen concentrations should not exceed the threshold levels in order to protect macroinvertebrate biodiversity in the Portoviejo River.

Low contribution of internal metabolism to carbon dioxide emissions along lotic and lentic environments of a Mediterranean fluvial network

AbstractInland waters are significant sources of carbon dioxide (CO2) to the atmosphere. CO2 supersaturation and subsequent CO2 emissions from inland waters can be driven by internal metabolism, external inputs of dissolved inorganic carbon (DIC) derived from the catchment, and other processes (e.g., internal geochemical reactions of calcite precipitation or photochemical mineralization of organic solutes). However, the sensitivity of the magnitude and sources of CO2 emissions to fluvial network hydromorphological alterations is still poorly understood. Here we investigated both the magnitude and sources of CO2 emissions from lotic (i.e., running waters) and lentic (i.e., stagnant waters associated to small dams) waterbodies of a Mediterranean fluvial network by computing segment‐scale mass balances of CO2. Our results showed that sources other than internal metabolism sustained most (82%) of the CO2 emissions from the studied fluvial network. The magnitude and sources of CO2 emissions in lotic waterbodies were highly dependent on hydrology, with higher emissions dominated by DIC inputs derived from the catchment during high flows and lower emissions partially fueled by CO2 produced biologically within the river during low flows. In contrast, CO2 emissions in lentic waterbodies were low, relatively stable over the time and the space, and dominated by DIC inputs from the catchment regardless of the different hydrological situations. Overall, our results stress the sensitivity of fluvial networks to human activities and climate change and particularly highlight the role of hydromorphological conditions on modulating the magnitude and sources of CO2 emissions from fluvial networks.

The paradox of expert judgment in rivers ecological monitoring

A great investment has been done in the last decades in the development of numerical and qualitative assessment methods to classify the ecological quality of water bodies. Yet, in spite of all attempts to avoid subjectivity, expert judgment is still used at numerous steps of the ecological classification and is considered by some authors as indispensible for management purposes. Thus, the aim of this study is to test the hypothesis that expert judgment, when done by the adequate experts (limnologists/river ecologist) with experience in the study area (i.e., natural conditions and expected communities), could be as good as quantitative indices and measures (i.e., result in the same classification), but quicker and with lower cost. For that we compared the classifications (on 13 aspects of rivers ecosystems) attributed by two experts to 20 sites (10 each) located in their study areas, with the classifications of ecological quality based on biological indices (for invertebrates and diatoms), hydromorphology and water chemistry, calculated by an independent team. Our results show that assessments made by experts and those calculated through indices (biological quality and hydromorphology) are globally very similar (RELATE test; Rho = 0.442; p < 0.001, 999 permutations). Most differences were of one class and experts tended to attribute a better condition than indices to the best quality sites but a worse condition to the worse quality sites. A Principal Components Analysis revealed that sites to which experts attributed a moderate quality had higher nitrate concentration and pH but were well oxygenated. The sites classified as poor and bad where those with stronger modifications in their habitats (given by the higher values of HMS). The difference between experts and indices is small but still represents 15% of sites, and includes both situations: the experts or the indices lead to the need of measures (i.e., classifications below class Good). Experts' evaluations on hydromorphological conditions of the channel and margins are also significantly correlated with the quality assessments made by the field team that has no experience in the study area (Rh0 = 0.518; p = 0.001; 999 permutation), indicating geographic independence in the expert judgment. We concluded that expert judgment could be used in the determination of streams and rivers ecological quality, saving money and time and helping to redirect monitoring funds to actual implementation of restoration measures. Yet, classification’ scoring methods may still be useful for a better targeting of restoration measures.

Assessment and classification of hydromorphological state of the Breń River

Abstract The paper presents the classification of the hydromorphological condition of the Breń River according to the River Habitat Survey (RHS). The research of the hydromorphological assessment of the Breń River, which is a right-bank tributary of the Vistula River and almost entirely flows through the area of the Dąbrowa Tarnowska district was conducted in June 2015. The research sites were situated on the border of the Tarnów Plateau and the Vistula Lowland. The Breń River in these sections flows through rural areas used for agricultural purposes with low-density housing. The analysis of qualitative parameters describing the morphological characteristics were based on two synthetic indices of stream quality: Habitat Quality Assesment (HQA) and Habitat Modification Score (HMS). The calculated numerical values of the two indices proved that the sections of the Breń River correspond with the third and fifth class, which means a moderate (III) and very bad (V) hydromorphological condition.

A fuzzy Bayesian approach to flood frequency estimation with imprecise historical information.

This paper presents a novel framework that links imprecision (through a fuzzy approach) and stochastic uncertainty (through a Bayesian approach) in estimating flood probabilities from historical flood information and systematic flood discharge data. The method exploits the linguistic characteristics of historical source material to construct membership functions, which may be wider or narrower, depending on the vagueness of the statements. The membership functions are either included in the prior distribution or the likelihood function to obtain a fuzzy version of the flood frequency curve. The viability of the approach is demonstrated by three case studies that differ in terms of their hydromorphological conditions (from an Alpine river with bedrock profile to a flat lowland river with extensive flood plains) and historical source material (including narratives, town and county meeting protocols, flood marks and damage accounts). The case studies are presented in order of increasing fuzziness (the Rhine at Basel, Switzerland; the Werra at Meiningen, Germany; and the Tisza at Szeged, Hungary). Incorporating imprecise historical information is found to reduce the range between the 5% and 95% Bayesian credibility bounds of the 100 year floods by 45% and 61% for the Rhine and Werra case studies, respectively. The strengths and limitations of the framework are discussed relative to alternative (non‐fuzzy) methods. The fuzzy Bayesian inference framework provides a flexible methodology that fits the imprecise nature of linguistic information on historical floods as available in historical written documentation.

The Hydromorphological Evaluation Tool (HYMET)

River engineering structures, such as bank protection or bed sills, act as constraints on the hydromorphology of rivers and limit morphodynamic processes. Accordingly, the deviations of a river's morphology from a natural reference condition have been attributed to the degree of artificiality in the observed river section and river restoration works mainly aimed at reducing artificial constraints within the river reach. Less attention has been drawn to alterations of the sediment continuum between sediment production in the river's catchment and downstream river reaches. However, the sediment supply from upstream is strongly reflected in the morphodynamics such as bar formation or the reworking of the riverbed. Any alteration of sediment supply may affect the morphological appearance of a reach and determine its deviation from an undisturbed condition.We introduce the Hydromorphological Evaluation Tool (HYMET), which accounts in a hierarchical procedure for sediment supply and sediment transfer as catchment and river network based preconditions for sustainable morphodynamics in river reaches. At the reach scale, artificiality and the sediment budget are assessed. In contrast to existing evaluation methods for assessing hydromorphological state, no reference condition is needed for determining hydro-morphological alterations. Here, with re-established sediment supply and reduced artificiality, a river reach is expected to develop morphodynamics that approach a morphodynamically and ecologically sustainable condition.Application to the Drau River showed that the alteration of sediment supply strongly affects the hydromorphological condition and thus the evaluation result of a restored reach, indicating the remaining potential for the re-initiation/re-establishment of morphodynamics through catchment-wide restoration plans.

Hydro-morphological classification of urban river sections based on LIDAR data

Abstract The assessment of hydro-morphological conditions is a part of ecological evaluation of water bodies. Many methods have been developed, but only a few of them are dedicated to urban rivers. Hydro-morphological classification would be a basis for river valley management, including restoration issue. One of the main problems in this assessment is the rate of change in urban catchment and urban river valley. Traditional methods, which are based on field study, are expensive and prolonged. The paper is focussed on using Light Detection and Ranging (LIDAR) data for classification of urban river sections. Although the assessment based on this data has some limitations, it is a good alternative to field study and may provide preliminary screen of the river valley. This material will make possible observation of river valley evolution in the future.