Hydromorphological Alterations Research Articles

Multipurpose Plans for the Sustainability of the Greek Lakes: Emphasis on Multiple Stressors

Lake Ecosystems have experienced a significant loss of their ecological value due to various human activities. It has been recognized that the continued alteration of freshwater biodiversity is not sustainable, and also, it has been realized that less modified freshwater ecosystems provide significant economic and social benefits to society. In Greece, changes in land and water management, driven by the increase in agricultural production and the urban expansion, have created multiple stressors on lentic ecosystems which cannot be ignored any longer. The objective of the present study is to describe some of these stressors, and to identify their impacts on Greek lakes. We collected an extensive dataset from twelve natural lakes using several metrics, also suggested by the Water Framework Directive (WFD), along with specific ecohydrological characteristics. Our results demonstrate severe impact on water quality and quantity with consequence to the lake’s functions, and extended eutrophication in almost all lakes. The Greek lakes have been subjected to various hydromorphological alterations, which affect their metabolism, while the aforementioned effects are further maximized due to particularities of the Mediterranean climate. The set up of good management practices through multipurpose management plans are also discussed.

The hydromorphological state in mountain rivers subject to human impacts: a case study in the North-West of Italy

The aim of this paper is the evaluation of the hydromorphological conditions of mountain rivers subject to extensive human activities. The hydromorphological state of a river depends on a high number of natural and anthropogenic characteristics, such as the presence of weirs, dams, or any other human infrastructure close to the riverbanks. The research focused on the mountain streams in Lake Maggiore catchment, located in the Italian Alps. The analyses were carried out using the method CARAVAGGIO (Core Assessment of River hAbitat VAlue and hydromorpholoGIcal cOndition), which complies with the EC Water Framework Directive. An intensive campaign of field surveys was conducted and a great amount of data was collected to obtain specific synthesis indexes. In particular, the Habitat Quality Assessment (HQA) and the Habitat Modification Score (HMS) were used to determine the diversification of natural characteristics and the level of hydromorphological alteration in the study area. Furthermore, a Lentic-lotic River Descriptor (LRD) was used in support of the information obtained by HQA and HMS. This research shows that the worst hydromorphological conditions can be found in rivers characterised by a high level of human constructions and hydropower plants. Finally, regression analyses were implemented to search a relationship between HQA, HMS and some morphological parameters. LRD was correlated to some hydraulic parameters. The results of this research are characterised by a high stochasticity.

Twenty years of research on water management issues in the Danube Macro-region — past developments and future directions

The Danube River–Danube Delta–Black Sea (DBS) region has witnessed major political, social and economic changes during the past three decades, which have profoundly affected the riverine, coastal and marine systems, their water management situation and the development of related research programmes. We reviewed the research activities in the DBS system of the past twenty years to determine the main funding bodies and to assess key research areas and how they varied over time and geographic region. As data basis we used a metadatabase filled with 478 projects addressing environmental and water management issues in the Danube River Basin, covering also the Danube Delta and the north-western Black Sea. As overall outcome extensive research efforts in the field of water management could be proven for the past two decades, despite the tumultuous times of political and economic transformations. One of the main findings was that EU funded projects played a key role for the development of transboundary research collaboration and were also the scientifically most productive one's. Historically, nutrient pollution was the main problem addressed, shifting to pollution in a broader sense and hydromorphological alterations in recent years. The newly arising challenges of climate change impacts and sediment management became important research questions in the last years, too. Most research was performed in the thematic field of navigation, followed by restoration and biodiversity issues. To meet all of the already identified and newly emerging challenges in the DBS System, cross-border and integrated (river-delta-sea) research activities are of major importance and have to be further promoted. We thus suggest drawing up a regional DBS Research Agenda linked to key challenges in water management to strengthen research collaboration and advance targeted scientific projects, an approach fostering also the scientific capacity in the region.

Do lake littoral benthic invertebrates respond differently to eutrophication, hydromorphological alteration, land use and fish stocking?

In order to provide adequate guidelines in freshwater management, managers need reliable bioindicators that can respond differently to varied stressors. Managers also have to consider hierarchical structure of environmental factors. Thus, our research aims to test the independence of taxa responses along environmental gradients and to examine in what order natural and anthropogenic factors constrain the structure of littoral benthic assemblages. The rank of explained variance of littoral benthic assemblage's variable group hierarchy was: land use > landscape characteristics > eutrophication > fish stocking > hydromorphological alteration. We determined nine gradients (two natural and seven stressor gradients), separated into five groups based on statistically significant differences in responsiveness of taxa. Apart from responsiveness to natural factors, littoral benthic invertebrates could be used as bioindicators for stressors reflecting urbanization, eutrophication, hydromorphological alteration and fish stocking. The taxonomical composition of littoral benthic invertebrates, especially when taxa with preference for certain relatively narrow environmental conditions along gradients are present, can be used to identify effects of key stressors. Our findings have profound implications for ecological assessment and management of lakes, as they indicate that benthic invertebrates can be used when the effects of multiple stressors need to be disentangled.

Disentangling the responses of boreal stream assemblages to low stressor levels of diffuse pollution and altered channel morphology

Non-point diffuse pollution from land use and alteration of hydromorphology are among the most detrimental stressors to stream ecosystems. We explored the independent and interactive effects of morphological channel alteration (channelization for water transport of timber) and diffuse pollution on species richness and community structure of four organism groups in boreal streams: diatoms, macrophytes, macroinvertebrates, and fish. Furthermore, the effect of these stressors on stream condition was evaluated by Ecological Quality Ratios (EQR) from the national Water Framework Directive (WFD) assessment system. We grouped 91 study sites into four groups that were impacted by either diffuse pollution or hydromorphological alteration, by both stressors, or by neither one. Macroinvertebrate richness was reduced by diffuse pollution, whereas other biological groups were unaltered. Hydromorphological modification had no effect on taxon richness of any of the assemblages. Community structure of all groups was significantly affected by diffuse pollution but not by hydromorphology. Similarly, EQRs indicated negative response by diatoms, macroinvertebrates and fish to diffuse pollution, but not to hydromorphological alteration. Agricultural diffuse pollution thus affected species identities and abundances rather than taxonomic richness. Our results suggest that channelization of boreal streams for timber transport has not altered hydromorphological conditions sufficiently to have a strong impact on stream biota, whereas even moderate nutrient enrichment may be ecologically harmful. Controlling diffuse pollution and associated land use stressors should be prioritized over restoration of in-stream habitat structure to improve the ecological condition of boreal streams.

Fuzzy cognitive mapping for predicting hydromorphological responses to multiple pressures in rivers

Summary Different pressures often co‐occur in rivers and act simultaneously on important processes and variables. This complicates the diagnosis of hydromorphological alterations and hampers the design of effective restoration measures. Here, we present a conceptual meta‐analysis that aims at identifying the most relevant hydromorphological processes and variables controlling ecological degradation and restoration. For that purpose, we used fuzzy cognitive mapping based on conceptual schemes that were created according to 675 scientific peer‐reviewed river hydromorphology studies. A model generated from this approach predicts responses that are consistent with common understanding of the direct interactions between hydromorphological pressures, processes and variables. However, it also leads to new knowledge beyond traditional hydromorphological models by dealing with the complex interactions of hydromorphology, vegetation, water chemistry and thermal regime. Water flow dynamics appeared as the most important of all hydromorphological processes affected by simultaneously interacting pressures. Relevant processes such as vegetation encroachment and sediment entrainment are closely linked to water flow. Synthesis and applications. Our results demonstrate the relevance of natural flow regime rehabilitation for river management. Hence, we suggest focusing primarily on rehabilitating the natural flow regime before carrying out extensive habitat restoration works. This challenging target in river rehabilitation could strongly increase the success of additional habitat restoration.

Functional trait composition of aquatic plants can serve to disentangle multiple interacting stressors in lowland streams

Historically, close attention has been paid to negative impacts associated with nutrient loads to streams and rivers, but today hydromorphological alterations are considered increasingly implicated when lowland streams do not achieve good ecological status. Here, we explore if trait-abundance patterns of aquatic plants change along gradients in hydromorphological degradation and eutrophication in lowland stream sites located in Denmark. Specifically, we hypothesised that: i) changes in trait-abundance patterns occur along gradients in hydromorphological degradation and ii) trait-abundance patterns can serve to disentangle effects of eutrophication and hydromorphological degradation in lowland streams reflecting that the mechanisms behind changes differ. We used monitoring data from a total of 147 stream reaches with combined data on aquatic plant species abundance, catchment land use, hydromorphological alterations (i.e. planform, cross section, weed cutting) and water chemistry parameters. Traits related to life form, dispersal, reproduction and survival together with ecological preference values for nutrients and light (Ellenberg N and L) were allocated to 41 species representing 79% of the total species pool. We found clear evidence that habitat degradation (hydromorphological alterations and eutrophication) mediated selective changes in the trait-abundance patterns of the plant community. Specific traits could distinguish hydromorphological degradation (free-floating, surface; anchored floating leaves; anchored heterophylly) from eutrophication (free-floating, submerged; leaf area). We provide a conceptual framework for interpretation of how eutrophication and hydromorphological degradation interact and how this is reflected in trait-abundance patterns in aquatic plant communities in lowland streams. Our findings support the merit of trait-based approaches in biomonitoring as they shed light on mechanisms controlling structural changes under environmental stress. The ability to disentangle several stressors is particularly important in lowland stream environments where several stressors act in concert since the impact of the most important stressor can be targeted first, which is essential to improve the ecological status.

Analysis of hydromorphological alterations of lakeshores for the implementation of the European Water Framework Directive (WFD) in Brandenburg (Germany)

Analysis of hydromorphological alterations of lakeshores for the implementation of the European Water Framework Directive (WFD) in Brandenburg (Germany)

Ecological assessment of morphological shore degradation at whole lake level aided by aerial photo analysis

Hydromorphological alterations of lake shores constitute an important pressure on Central European lakes. The local ecological effects of such alterations can be assessed by multimetric assessment methods based on eulittoral macroinvertebrate communities. However, such tools so far only enable a local assessment even if the European Union Water Framework (EU WFD) requires an assessment at whole-lake level. Since due to time and financial constraints it is not feasible to perform small-scale macroinvertebrate assessments over the whole length of the lake shore, the site-specific ecological assessment result needs to be extrapolated. In this study, we analyse the use of a physical habitat survey method including both ground surveys and aerial photo analysis (HML = HydroMorphology of Lakes survey protocol) to enable an extrapolation from local to whole lake ecological assessment. For that purpose, we correlated individual macroinvertebrate metrics as well as results of a multimetric macroinvertebrate-based index (I) with the areal cover of surrounding natural shore elements, (II) with the hydromorphological impact within an encircling rectangle around the macroinvertebrate sampling site, and (III) with the hydromorphological impact in the adjacent epi-, euand sublittoral subsegments. Building up on this, an ecological whole lake assessment was achieved by averaging multimetric index scores calculated for each subsegement based on a regression equation between the multimetric index and the hydromorphological impacts in the three subsegments. This whole lake assessment approach can most likely be applied to geographical regions outside Central Europe and lake types not analysed here (fluvial lowland lakes, prealpine/alpine lakes), but more studies are necessary to verify this. Eventually, the extrapolation presented here may complement existing lake assessments under the EU WFD solely focusing on water quality so far.

Implications of hydromorphological alterations to the littoral zone for freshwater ecosystem functioning

Implications of hydromorphological alterations to the littoral zone for freshwater ecosystem functioning

The effect of river damming on vegetation: is it always unfavourable? A case study from the River Tiber (Italy).

River damming leads to strong hydromorphological alterations of the watercourse, consequently affecting river vegetation pattern. A multitemporal and spatial analysis of the dam effect on composition, structure and dynamic of the upstream vegetation was performed on Tiber River at Nazzano-dam (Rome). The main research questions were as follows: How does plant landscape vary over time and along the river? Where does the dam effect on vegetation end? How does naturalistic importance of the vegetation affected by damming change over time? Data collection was performed mapping the vegetation in aerial photos related to the period before (1944), during (1954) and after dam construction (1984, 2000). The plant landscape has significantly changed over time and along the river, particularly as a result of the dam construction (1953). The major vegetation changes have involved riparian forests and macrophytes. Dam effect on vegetation is evident up to 3 km, and gradually decreases along an attenuation zone for about another 3 km. Despite the fact that the damming has caused strong local hydromorphological modification of the river ecosystem transforming it into a sub-lacustrine habitat, it has also led to the formation of wetlands of considerable naturalistic importance. Indeed, in these man-made wetlands, optimal hydrological conditions have been created by favouring both the expansion of pre-existing riparian communities and the rooting of new aquatic communities, albeit typical of lacustrine ecosystems. Some of these plant communities have become an important food resource, refuge or nesting habitats for aquatic fauna, while others fall into category of Natura 2000 habitats. Therefore, river damming seems to have indirectly had a "favourable" effect for habitat conservation and local biodiversity.

The future water environment — Using scenarios to explore the significant water management challenges in England and Wales to 2050

Society gets numerous benefits from the water environment. It is crucial to ensure that water management practices deliver these benefits over the long-term in a sustainable and cost-effective way. Currently, hydromorphological alterations and nutrient enrichment pose the greatest challenges in European water bodies. The rapidly changing climatic and socio-economic boundary conditions pose further challenges to water management decisions and the achievement of policy goals. Scenarios are a strategic tool useful in conducting systematic investigations of future uncertainties pertaining to water management. In this study, the use of scenarios revealed water management challenges for England and Wales to 2050. A set of existing scenarios relevant to river basin management were elaborated through stakeholder workshops and interviews, relying on expert knowledge to identify drivers of change, their interdependencies, and influence on system dynamics. In a set of four plausible alternative futures, the causal chain from driving forces through pressures to states, impacts and responses (DPSIR framework) was explored. The findings suggest that scenarios driven by short-term economic growth and competitiveness undermine current environmental legislative requirements and exacerbate the negative impacts of climate change, producing a general deterioration of water quality and physical habitats, as well as reduced water availability with adverse implications for the environment, society and economy. Conversely, there are substantial environmental improvements under the scenarios characterised by long-term sustainability, though achieving currently desired environmental outcomes still poses challenges. The impacts vary across contrasting generic catchment types that exhibit distinct future water management challenges. The findings suggest the need to address hydromorphological alterations, nutrient enrichment and nitrates in drinking water, which are all likely to be exacerbated in the future. Future-proofing river basin management measures that deal with these challenges is crucial moving forward. The use of scenarios to future-proof strategy, policy and delivery mechanisms is discussed to inform next steps.

Impacts of land use conflicts on riverine ecosystems

Starting from a diagnosis of areas with different environmental land use conflicts located in various rural sub-basins of the River Sordo basin (northern Portugal), the present study analyzed the ecological quality of surface water in small mountain streams to establish a relationship between land use, water and aquatic biota. Environmental land use conflicts were set up on the basis of land use and land capability maps, coded as follows: 1 – agriculture, 2 – pasture, 3 – pasture/forest, and 4 – forest. Land capability was assessed by the ruggedness number methodology (RN). The difference between the codes of capability and use defines a conflict class, where a negative or null value means no conflict and a positive value means class i conflict. Within and without the conflict areas, ecological quality of surface water was evaluated by the metrics EPT taxa, IPtIN index, diversity of Shannon–Wiener and Evenness index. Macroinvertebrate communities are strongly correlated to conflict classes, because sites without (reference sites) or with minor physicochemical and hydromorphological degradation (Class 1) presented high diversity, evenness, EPT taxa and IPtIN index, while more impacted sites (Class 2) presented an ecological status not fulfilling the demands of the European Union Water Framework Directive (2000/60). The present study indicates a significant impact of land use on water quality which has straight influence on the distribution of biota, emphasizing the key role of riparian vegetation in the conservation of aquatic ecosystems. The highest impacts on macroinvertebrate assemblages were associated with changes in water quality parameters such as temperature, oxygen saturation (%), turbidity, total suspended solids (TSS), nitrates, phosphates and sulphates, conductivity and dissolved oxygen, as well as hydromorphological alterations driven by the total absence of riparian vegetation as a consequence of terrace building, agriculture and the resectioning/reinforcement of the banks associated with the culture of vine. Macroinvertebrates proved reliable to distinguish conflict classes and separate seasons. The main conservation measures required to improve the conflict areas in the short and medium term mainly include the adoption of agroforestry practices as these not only improve the quality of water and soil, maintaining land resources over a long period of use, but also brings many benefits to the landowner.

Providing Longitudinal Connection In Case Of Cross Sluicing On Water Bodies In Banat Hydrographic Area

Abstract On Banat Hydrographic Area level, there are a series of works which put hydrological pressures on bodies of water: accumulations, damming, water diversions, regulations, shore protection, etc. These works were created in order to ensure water demand, defend against floods, regulate discharges, and combat humidity excess. Speaking justly, they have an important socioeconomic role. Among the negative effects of longitudinal connection interruption of water bodies we can mention, the risk of not achieving the positive ecological potential of water bodies in accordance with the Water Framework Directive, the reduction of the aquatic biodiversity, the reduction or even extinction of certain aquatic species and the alteration of the flow process. Because the negative effects of the hydromorphological alterations, especially those due to the interruption of the longitudinal connection, have a significant impact on the aquatic biodiversity. At Banat Hydrographic Area level, a series of measures, have been identified for the rehabilitation of the affected water courses: the removal of the hydrotechnical constructions from the water body if they have lost their functional features, building of passages for the migration of the ichthyofauna, reconnecting of the affluents and the disconnected arms as well as other measures intended to bring things back to their natural state. The implementation of these measures is made according to the importance and the extent of their positive impact as opposed to the negative effect that might occur as a consequence of their application. Analyzing the measures aforementioned and taking into consideration the characteristics of the hydromorphological pressures on water bodies in Banat Hydrographic Area, a number of measures regarding control are supplied in this paper.

Responses of Mediterranean aquatic and riparian communities to human pressures at different spatial scales

Mediterranean river ecosystems are subjected to intense human pressures and impacts that affect both their aquatic and riparian communities. However, given their stratified position in the river ecosystem and varying ecological requirements, aquatic and riparian communities can respond differently to such pressures. These biological responses could also vary depending on the nature of the disturbances, the spatial scale considered and the indicators used as response variable. Here, we aim to assess the influence of the main human pressures present in Mediterranean rivers (agricultural land use and hydromorphological alteration) on the biodiversity and ecological condition indicators of both riparian and aquatic communities at two spatial scales: reach and basin. For this purpose, a total of 56 sampling sites covering the study area (Segura basin, SE Spain) were surveyed. Water beetles and woody riparian vegetation richness were used respectively as biodiversity surrogates of aquatic and riparian communities, and the Iberian Biomonitoring Working Party (IBMWP) and Riparian Quality Index (RQI) were used to assess the ecological status of both communities. As expected, we found a general decrease in both richness and ecological condition when human pressures increased, regardless of the spatial scale considered. Nonetheless, agricultural land use was the main pressure explaining riparian richness and quality, whereas aquatic communities’ responses were highly related to hydromorphological alteration. Contrary to expected, in general, variables at basin scale had a greater effect than those variables operating at local scale. In addition, ecological condition indices responded more clearly to human pressures than biodiversity surrogates. Therefore, land use and hydrological planning at basin scale are essential complements to conservation and restoration efforts, traditionally carried out at reach scale, in order to maintain stream ecosystem integrity and biodiversity.

An invertebrate predictive model (NORTI) for streams and rivers: Sensitivity of the model in detecting stress gradients

NORTI (NORThern Spain Indicators system) is a predictive model for assessing the ecological status of rivers of Northern Spain based on invertebrates. The system can be used to assign any test site to a type of river under minimal disturbed conditions. Macroinvertebrates were sampled with a multihabitat approach from 676 sites covering the variation in environmental conditions across Northern Spain, between 2000 and 2008 (n=1421 samples), including a spatial network of 108 reference sites selected by the absence of significant pressures. A multinomial logistic regression was conducted using the GAAC cluster-derived groups of reference sites as response variable. Obligatory typology factors, following WFD System A, were included as forced entry terms in the model, other potential predictors were selected using a forward stepwise procedure. Ecological quality ratios (EQRs) were estimated from the observed similarity between the faunal composition of the sample of interest (test sample) and the expected median similarity for the reference community of each river type. The model predictions as EQRs responded significantly to the most important pressures: sewages inputs, eutrophication, hydromorphological alterations, and intensive and low intensity agriculture, demonstrating its accuracy in detecting impact in Northern Spanish streams and rivers.

Biodiversity of traits and species both show weak responses to hydromorphological alteration in lowland river macroinvertebrates

Summary Lotic ecosystems worldwide are being increasingly modified hydromorphologically, for example, by damming, fragmentation, flow regulation and channel modification. Serious threats to riverine biodiversity are suspected, yet available field data are few and rarely address the various taxonomic, functional and phylogenetic components of biodiversity. We examined benthic macroinvertebrate diversity along a gradient of hydromorphological alteration across 65 lowland river sites in the Netherlands, Germany and Poland. We calculated eight metrics describing taxonomic diversity (richness, rarefied richness, Shannon's and Simpson's diversity, Pielou's evenness), functional diversity (mean trait diversity) and phylogenetic diversity (mean taxonomic distinctness and its variance). Threshold Indicator Taxa ANalysis (TITAN) and Non‐metric Multidimensional Scaling (NMS) showed detailed changes in taxonomic and trait composition, respectively, with increasing hydromorphological alteration. TITAN revealed a gradual turnover under increasing impact in which taxon losses were almost balanced by gains. NMS illustrated a high degree of concordance in the traits possessed by the taxa lost and gained at the gradient's end points. Although a biologically meaningful hydromorphological gradient was evident, the biodiversity response was modest (Spearman's ρ < |0.32| for all metrics). Pielou's evenness and mean taxonomic distinctness actually increased at impaired sites. Our results suggest that taxonomic and trait replacement with hydromorphological alteration is not followed by changes in whole‐community diversity. This implies some redundancy in these systems, with ecologically similar species replacing those lost through environmental change. The results highlight how whole‐community‐based diversity, although frequently calculated and interpreted for decades in ecology and conservation biology, is not the all‐purpose concept to detect and assess the various facets of biodiversity loss. Therefore, we suggest that concerted effort is needed to develop and test novel indicators of biodiversity, capable of detecting biodiversity loss, or other changes, in response to the main environmental stressors of lotic ecosystems.

Importance of multi-dimensional morphodynamics for habitat evolution: Danube River 1715–2006

Human-unimpaired braided and anabranched river systems are characterized by manifold multi-dimensional exchange processes. The intensity of hydrological surface/subsurface connectivity of riverine habitats depends on more than regular or episodic water level fluctuations due to the hydrological regime. Morphodynamic changes are also a basic underlying factor. In order to provide new insights into the long-term habitat configuration of large rivers prior to channelization, this study discusses the hydromorphological alterations of an alluvial section of the Austrian Danube based on historical records from 1715 to 2006. The study combines the analysis of habitat patterns and intensity of hydrological connectivity over the long term with the reconstruction of short-term morphodynamic processes between 1812 and 1821. The main research questions are (1) whether the intensive morphodynamics prior to channelization are reflected by a marked variation in habitat patterns or whether the variation remained within a small range, and (2) which fluvial processes contributed to the evolution of the habitat configuration identified.The study reveals that the mean variations in the habitat patterns and the intensity of hydrological connectivity were only between 3% and 10% before 1821, although the river landscape was subject to intensive fluvial disturbances. An exception was the expansion of aquatic habitats between low and mean flow, which deviated by 15%. Habitat evolution was affected by morphodynamic processes occurring across different temporal scales. Both gradual channel changes such as incision or migration and sudden processes such as avulsions (cut-offs) contributed to the patterns identified. Locally, sudden channel changes extensively altered the habitat conditions with regard to hydrological surface/subsurface connectivity. Such alterations foster or restrain the potential evolution and the ecological succession of the riparian vegetation at the respective sites. On a larger spatial and temporal scale, however, the changes in the intensity of hydrological connectivity were largely balanced. The results support the hypothesis that a resilient “shifting mosaic steady-state” existed over the long term as long as the framework conditions (e.g. climate) did not significantly change. The habitat mosaic representing different types and different ages potentially allowed many riverine species to co-exist in an environment with frequent perturbations. From 1821 onwards, river engineering measures significantly altered habitat patterns and severely truncated the potential of the system to recover from disturbances.

A pragmatic approach to define the ecological potential of water bodies heavily modified by the presence of ports

Abstract Due to the great number of ports along the European coast, defining the ecological potential of heavily modified water bodies (HMWBs) by the presence of ports is crucial in the development of river management plans. Numerous approaches have dealt with the assessment of the ecological status of natural water bodies, but there are few which specifically cover HMWBs. This contribution proposes pragmatic approaches to define the ecological potential of port areas. Besides being coherent with the hydromorphological alterations, the methodologies developed ensure the functioning of the ecosystem while recognizing that the communities and conditions found in HMWBs are highly determined by the major hazards associated to port activities. The main output is a versatile site-specific approach able to identify the best possible indicators and reference conditions (maximum ecological potential; MEP) to evaluate the ecological potential in port areas. The implementation at the port of Santander stressed the importance of considering water, sediments and biological indicators to evaluate the ecological potential, confirming sediments as the main testimony of the contaminant episodes.

The status of the Danube River sediment regime and morphology as a basis for future basin management

Hydromorphological alterations of large rivers are evident and have to be related to multiple anthropogenic pressures. Here we present the results of an integrated study concerning the actual status of the hydromorphology of the Danube River Basin that shows the sediment regime features a heavily disturbed system at various scales. Combined impacts of flood protection, navigation, and hydropower measures applied over a long period of time have been identified based on the river scaling concept as being responsible for these specific alterations (lack of bed load and suspended load in the remaining free-flowing sections). Moreover, long sections of the Danube River have been narrowed, channelized, disconnected from floodplains, and morphologically degraded over the last 200 years. This has caused increased bottom shear stresses, increased sediment transport capacities, and in addition a lack of lateral self-forming processes and corresponding reduced morphodynamics in the non-impounded sections. As a consequence of both, longitudinal and lateral disturbances of the sediment supply and additional impacts of the channelization, in opposition to a surplus of sediments in impoundments the remaining free-flowing sections are subject to various forms of river bed degradation. Such degradation or river bed incision leads to a loss of instream structures in general, with a disappearance of gravel bars at the Upper Danube and changes to sand bars in the Lower Danube. Hence, for river systems and large river basins, it has to be stated that the preservation and restoration of sediment continuity and morphodynamics is one of the most relevant issues for river engineering and ecology. This has to be considered especially for the implementation of legal directives and/or future river basin management plans.