Danube Floodplain Research Articles

Floodplains - Links between Countries and Landscapes

The primary function of floodplains remains to be to ensure the safe passage of flood waves. As flood control problems are serious along some river sections, this also requires international cooperation. In landscape ecology, floodplains perform two related functions: they are riparian buffer zones (vital for maintaining river water quality) on the one hand and ecological corridors (ensuring connectivity and high biodiversity) on the other. Floodplain wetlands play an important part of the ecological integrity of riverine ecosystems as they fundamentally influence the ecological status of adjacent water bodies. It is all the more important since along most of its length the Danube crosses densely inhabited areas with intensive agriculture, large-scale industries and welldeveloped communication networks. Consequently, environmental pressure on the active and protected floodplains is of considerable extent and sharp conflicts arise between different land use types. Land use types promoting the fulfilment of the riparian buffer zone function must have priority. Unfortunately, only restricted sections of the Danubian floodplain are retained in seminatural conditions. In the Danube catchment 80% of the former wetlands are now disconnected and cannot fulfil their nature conservation role. The national NATURA 2000 networks are so much dependent on seminatural riparian ecosystems that they cannot be efficient without floodplain restoration measures. Predictable climate change tendencies (increasing drought liability) are also a threat to the survival of floodplains as ecological corridors. Remediation efforts are necessary along extensive floodplain sections and better connectivity is identified as an important target. According to the Danube River Basin District Management Plan (ICPDR 2009, p. 76):”The ICPDR’s basin-wide vision is that floodplains/wetlands in the entire DRBD are re-connected and restored. The integrated function of these riverine systems ensures the development of self-sustaining aquatic populations, flood protection and reduction of pollution in the DRBD.”

Spatio-temporal changes in land cover and aquatic macrophytes of the Danube floodplain lake

The aquatic vegetation of Číčov Lake in the Danube floodplain, which is listed in the Ramsar Convention, was investigated to address three main questions: (1) how have landscape composition and the structures of the lake and its buffer zone changed from the mid-20th century; (2) how have species richness and the abundance of the aquatic macrophyte assemblage in this lake ecosystem changed over the last 34 years; and (3) which landscape metrics can best explain these temporal changes for floating-leaved macrophytes? Two methodological approaches, remote sensing and botanical field surveys, were applied. Historical (1949, 1970, 1990) and contemporary (2006) aerial photographs were analysed to determine land cover. Landscape configuration and structure were analysed using eight landscape metrics selected in advance to measure spatio-temporal changes and the fragmentation of the lake ecosystem and its corresponding buffer zone. The species diversity, abundance and distribution of true aquatic macrophytes were surveyed eleven times in five survey stretches between 1973 and 2007. At the landscape level, a decrease in the area covered by floating-leaved macrophytes, as well as an increase in open water surface and fragmentation of the land cover classes in the lake ecosystem, were recorded from 1949 to 2006. Overall, 30 true aquatic macrophytes were found from 1973 to 2007. Species richness did not change considerably, but the abundance of aquatic species fluctuated over the years. Three groups of true aquatic vegetation, based on common structural characteristics, were found in 1973–1983, 1989–2002, and 2004–2007 over the last 34 years. The landscape metrics NP, PD, LPI, and SHDI, which all express patterns of landscape fragmentation mostly indicate temporal changes in floating-leaved macrophytes.

Fluvial micromorphology influenced by tillage on a Danubian floodplain in Hungary

Fluvial micromorphology influenced by tillage on a Danubian floodplain in Hungary

Forest Habitat Change Dynamics in a Riparian Wetland

Our study aims at monitoring ecosystem dynamics in the Szigetköz Danube floodplain (Hungary), where the wetland communities have been seriously affected by the abrupt hydrological changes after the Danube-diversion in 1992. Wetland habitats were mapped in the last years for a chosen area, based on a comparable use of archived analogue and digital aerial images and available silvicultural and botanical inventories. During the object-based image analysis the classification was mainly based on texture measures. The resulting map time series show habitat borders for each year and present the changes separately for each class. The method is suitable for the characterization of spatial and temporal structure of wetland land cover in a realistic way.

Natural and Man-Induced Hazards Along the Danube, between Rast and Gighera Settlements, with a Special View on the 2006 Flood

Natural and Man-Induced Hazards Along the Danube, between Rast and Gighera Settlements, with a Special View on the 2006 Flood The paper discusses the natural and man-induced hazards in the Rast-Gighera sector of the Danube Floodplain, an area displaying asymmetric character, with the high and steep slopes of the Prebalcanic Tableland dominating the low Romanian floodplain. The subject regards an acute present problem, the necessity to improve the management of dangerous phenomena included among the objectives for this millennium. Moreover, the paper regards a space with an exceptional natural heritage that has been seriously transformed by man, the natural-human opposition becoming the key-element of the region. The complexity of the subject is given by the plurality of causes that lead to the genesis of hazards. Their nature, frequency and intensity, along with other factors of psychological or economic nature imply different answers from the part of the affected population. In the past, the region was characterised by the significant presence of swampy areas, lakes and ponds connected to the Danube through secondary branches, being under the influence of the level oscillations of the river. The relief was strongly modified, especially during the last hundred years, the human factor exerting an important influence, mainly through flood-control dykes and dams, networks of irrigation and drainage channels, deforestation, so that extended surfaces that had been naturally covered by waters and forests were converted to agriculture.

Multiple origins of European populations of the giant liver fluke Fascioloides magna (Trematoda: Fasciolidae), a liver parasite of ruminants

The giant liver fluke, Fascioloides magna, a liver parasite of free-living and domestic ruminants of Europe and North America, was analysed in order to determine the origin of European populations and to reveal the biogeography of this originally North American parasite on the European continent. The variable fragments of the mitochondrial cytochrome c oxidase subunit I (cox1; 384bp) and nicotinamide dehydrogenase subunit I (nad1; 405bp) were used. Phylogenetic trees and haplotype networks were constructed and the level of genetic structuring was evaluated using population genetic tools. In F. magna individuals originating from all European foci of infection (Italy, Czech Republic and Danube floodplain forests involving the territories of Slovakia, Hungary and Croatia) and from four of five major North American enzootic areas, 16 cox1 and 18 nad1 haplotypes were determined. The concatenated sequence set produced 22 distinct haplotypes. The European fluke populations were less diverse than those from North America in that they contained proportionately fewer haplotypes (eight), while a more substantial level of genetic diversity and a greater number of haplotypes (15) were recorded in North America. Only one haplotype was shared between the European (Italy) and North American (USA/Oregon and Canada/Alberta) flukes, supporting a western North American origin of the Italian F. magna population. Haplotypes found in Italy were distinct from those determined in the remaining European localities which indicates that introduction of F. magna to the European continent occurred more than once. In the Czech focus of infection, a south-eastern USA origin was revealed. Identical haplotypes, common to parasites from the Czech Republic and from an expanding focus in Danube floodplain forests, implies that the introduction of F. magna to the Danube region came from an already established Czech focus of infection.

Colonisation of temporary macrophyte substratum by midges (Chironomidae: Diptera)

This study investigates a phytophylous community of Chironomidae larvae on the submerged plant species Myriophyllum spicatum L. in a eutrophic lake (Lake Sakadas, Danube floodplain area in Croatia) during summer 2004. This macrophyte species appeared for the first time in the lake in 2004, lasted approximately three months and was considered as a temporary habitat. The chironomid community was very abundant in the stands of this macrophyte species, which developed at three sites. The recorded species belong to three subfamilies: Chironominae (Chironomini and Tanytarsini), Orthocladiinae and Tanypodinae. Species composition varied in time, though Orthocladiinae with their representative Cricotopus sylvestris gr. dominated throughout the entire sampling period, accounting for approx. 60% of the total community. However, the presence of this species group experienced a marked drop to only 10% in September when Chironomini larvulae and Paratanytarsus sp. prevailed. Furthermore, the share of Endochironomus albipennis (Meigen 1830) in relation to other species was also consistently higher. NMDS ordination and cluster analysis separated three main colonization periods based on larval abundance. RDA analysis indicated the influence of environmental variables, especially Secchi depth, macrophyte dry weight, depth and water temperature, on chironomid community structure.

Regeneration of gallery forests of Béda by natural tree species

Instead of high value willow-poplar galleries and ash-oak-elm galleries stands of non-indigenous species are present at many sites of the flood plain of Danube in the Béda-Karapancsa Region of the Danube Drava National Park. According to the Act of Nature Conservation in Hungary minders of the territories are obligated to change non-indigenous tree species to natural tree species in all forest stands (e.g. monocultures), that are on protected areas. Change of forest structure has to be determined by the recent type of stand, the future stand and the site; its speed is fitted to the whole territory. The affects of water regulation works on the area must be taken in regard. It is necessary to monitor the results of the changes of forest structure by indicators of naturalness. It can be done by the method of naturalness value of forest stands (TERMERD).

The usage of the historical cartographic datasets and the remote sensing data for the better understanding and mapping of the 2006 Danube floods in Romania

The advantages brought by high resolution satellite data in activities related to flood mapping and flood monitoring are well know in the scientific community. The paper aims to prove that slighter older geospatial documents, such as historical maps, are also a valuable resource for cartographers and decision makers to achieve a better understanding of flood patterns and evolution. Some preparatory actions are needed in order to integrate the old maps into GIS environments for advanced analysis. This includes scanning, color enhancements, georeferencing, reprojection and metadata creation. To illustrate the process, the paper includes a real case scenario: the April 2006 Danube River flood. For one of the most affected sectors along the Danube, close to Rast village, three generations of historical maps (the Austrian 1:200 000 ‘degree maps’, the Romanian 1:20 000 ‘Lambert-Cholesky’ maps and the Soviet Union 1:100 000 ‘Gauss-Krüger’ maps) were processed and included in a large repository. At any time, the maps can be identified and accessed through open standard protocols like CSW and WMS. In this way, we were able to integrate and analyze the flood water masks, extracted from satellite data, along with the historical data sets. The results were very promising. It was possible to understand some flood patterns and to clearly demonstrate that, after the dike failure, the water filled up an area which in the past, before river regulation, was the natural Danube floodplain.

Herb layer production in the willow stands on the Danubian soft-wood floodplain forest sites

Herb layer production in the willow stands on the Danubian soft-wood floodplain forest sites

Dual impact of the flood pulses on the phytoplankton assemblages in a Danubian floodplain lake (Kopački Rit Nature Park, Croatia)

There are several conflicting hypothesis that deal with the influence of flooding in the natural river–floodplain systems. According to the Flood Pulse Concept, the flood pulses are not considered to be a disturbance, while some recent studies have proven that floods can be a disturbance factor of phytoplankton development. In order to test whether flooding acts as a disturbance factor in the shallow Danubian floodplain lake (Lake Sakadas), phytoplankton dynamics was investigated during two different hydrological years—extremely dry (2003) without flooding and usually flooded (2004). A total of 18 phytoplankton functional groups were established. The sequence of phytoplankton seasonality can be summarized P/D → E (W1, W2) → C/P (only in potamophase) → S2/H1/SN/S1 → W1/W2 → P/D. The canonical correspondence analysis (CCA) demonstrated that the water level was a significant environmental variable in 2004. Due to the higher total biomass of Bacillariophyceae established under potamophase conditions, floodings in the early spring seem to be a stimulating factor for phytoplankton development. On the other hand, the flood pulses in May and June had dilution effects on nutrients, so that a significantly lower phytoplankton biomass was established indicating that flooding pulses can be regarded as a disturbance event. Such conditions supported diatom development (D, P, C species) and prolonged its dominance in the total phytoplankton biomass. A long-lasting Cyanoprokaryota bloom (various filamentous species—S1, S2, SN and H1 representatives) with very high biomass characterized the limnophase (dry conditions) in summer and autumn of both years. In-lake variables (lake morphology, internal loadings of nutrients from sediments, light conditions) seem to be important for the appearance of Cyanoprokaryota bloom. The equilibrium phase was found during the Cyanoprokaryota bloom only in the extremely dry year. This study showed that depending on the time scale occurrence, flood pulses can be a stimulating or a disturbance factor for phytoplankton development in Lake Sakadas.

Distribution of cadmium among geochemical fractions in floodplain soils of progressing development

Initial soil development in river floodplains influences soil properties and processes. In this study, suites of young floodplain soils sampled at three European rivers (Danube/Austria, Ebro/Spain and Elbe/Germany) were used to link soil development to the soils' retention capacity for cadmium. Geochemical fractionation of original and metal-spiked soils was conducted. Cadmium remained in weakly bound fractions in both original and spiked soils, representing an entirely different behaviour than observed for copper in an earlier study. The tendency of incorporation into more stable forms over time was only slightly expressed. Correlation analysis revealed the involvement of different sorption surfaces in soil, with no single soil constituent determining cadmium retention behaviour. Nevertheless, in the calcareous soils of the Danube floodplain, we found increased cadmium retention and decreased portions of desorbable cadmium with progressing soil development.

The composition and richness of Danubian floodplain forest land snail faunas in relation to forest type and flood frequency

The species richness and composition of land snail assemblages in 42 floodplain forest sites along the Danube River in Slovakia were studied to find the main ecological gradients responsible for the variation in the faunas. We found just one, but steep, ecological gradient influencing the variation of snail species composition among different floodplain forest types, reflected in the first detrended correspondence analysis axis, which explained 29.6% of total variation. Site scores on this axis were significantly correlated with site humidity (rs ¼ 20.868; P , 0.001). Significant loading on the first axis was also found for flood frequency and several vegetation descriptors. Species composition mainly reflected differences between sites without floods and the others. Species richness as well as total abundances of live individuals were not significantly controlled by any explanatory variable, although some trends could be discerned. Considering vegetation classification, substantial differences were observed between wet softwood floodplain forests and the remaining types, drier softwood forests and different types of hardwood forests, which were impossible to distinguish based on land snail assemblages. The results are discussed in relation to earlier descriptive studies, and in terms of the conservation of these threatened habitats.

Past On-Site Experience, Crowding Perceptions, and Use Displacement of Visitor Groups to a Peri-Urban National Park

Past on-site experience was linked to the crowding perceptions and use displacement of 383 on-site visitors to the peri-urban Danube Floodplains National Park, Austria. Three visitor groups were determined according to their area experience: local residents from Vienna and rural communities, having the highest level of experience; regional visitors from the city and eastern Austria; and tourists from Austria and abroad with the lowest degree of experience. Crowding perceptions were significantly different across the user groups. More than 50% of local residents perceived the national park as crowded, whereas only 27% of regional visitors and 19% of tourists reported such an evaluation. Even among local residents and regional visitors, respondents with more on-site experience expressed a greater impression of a crowded park. Differences in crowding evaluations between local rural and urban residents and between regional rural and urban visitors were not found. For 27% of local residents and 15% of regional visitors, use levels were so unacceptable that they displaced temporally and spatially, whereas use displacement was relatively irrelevant for tourists. The use displacement strategies involved differ among the three user groups. Management implications were discussed, taking the specific situation of the small national park on the urban-rural fringe into consideration.

Realistic restoration of the Gemenc region of the Danubian floodplain based on hydroecological priorities

Realistic restoration of the Gemenc region of the Danubian floodplain based on hydroecological priorities

Optimised management strategies for the Biosphere reserve Lobau, Austria - based on a multi criteria decision support system

Without sustainable rehabilitation measures, the Lobau, a freshwater Biosphere Reserve, will soon became a primarily terrestrial ecosystem with major implications for its rich aquatic and amphibic biodiversity. An innovative ecosystem management scheme for this Danube floodplain needs to optimally balance between conservation and restoration objectives and to harmonize the partly competing ecologic and socio-economic requirements for the next 40 years. Therefore, we present a project dealing with the development of a multi-criteria Decision Support System (DSS), based on interdisciplinary historical analyses and state-of-the-art ecosystem modelling. The DSS will assists multiple stakeholders in finding coherent and realistic management alternatives, by linking all objectives and measures in a transparent and reproducible way.

Long-term changes in cladoceran assemblages in the Danube floodplain area (Slovak–Hungarian stretch)

In this paper, the distribution of Cladocera species in the different sampling sites: the main channel/old river bed, parapotamal type side arms and plesiopotamal side arms, is described. The structure of cladoceran assemblages in the by-passed Danube section and in the adjacent floodplain water bodies has changed since the Gabčíkovo hydropower plant was put into operation. Great changes have been observed in the previous parapotamal side arm situated between river km 1840 and 1820, artificially fed with water from the head-race canal. The dominance of tychoplanktonic (benthic and phytophilous) species has increased, while the typical euplanktonic species have disappeared. Three characteristic groups of cladoceran assemblages were recorded when a different type of habitat was taken into consideration. Euplanktonic cladocerans prevailed on all sampling sites before damming. In periods after damming, littoral species, and later also a euplanktonic forms, dominated on the main channel sampling sites. In parapotamal and plesiopotamal side arms with rich littoral macrovegetation during periods after damming, phytophilous cladoceran species were the ones with the highest occurrence. The samplings from the first time period were rather homogenous. The samplings from the second and third period were more similar when considering the sample site than regarding the time period. In total, 64 cladoceran species were recorded in the course of 13 years (from 1991 to 2004). The increase in number of Cladocera species from 1991 to 2004 was significant. Chydorus sphaericus was found to be the most widely distributed species in the study area. The finding of Disparalona hamata is the first faunistic record from the central part of the Danubian watersheds.

Evaluating Visitor-Monitoring Techniques: A Comparison of Counting and Video Observation Data

Two visitor-monitoring methods, video monitoring and counts by human observers, were compared in order to identify and evaluate their respective advantages and disadvantages. The analysis considered user numbers, user type (walkers, dog walkers, bicyclists, and joggers) and group size of visitors. Remarkable differences were found between the two methods for user type and use levels. At low use levels, evaluations based on video monitoring resulted in fewer single bicyclists compared to counts by human observers, whereas at high use levels, human observers counted fewer walkers and bikers than video-interpreters. Based on this comparative analysis, we derive recommendations for more effective visitor-monitoring approaches. All data were collected during a visitor-monitoring project in the Danube Floodplains National Park in Austria between 1998 and 1999.

The Impact Of Water Sports On Heron Behavior During Non-Wintering Season In Austria's Danube Floodplains National Park

Austria's Danube Floodplains National Park is a prime example for management issues in a protected area with high recreational use. This study focuses on the disturbances of grey herons (Ardea cinerea) and silver herons (Casmerodius albus) caused by canoeists, which were inventoried using standardized ecological observation techniques by measuring the distances of flight. Survey data about the canoeists' characteristics and their awareness of their disturbance on the avifauna were obtained from on-site interviews, conducted when canoeists were leaving the area. Video-monitoring was undertaken to provide long-term quantitative data about use levels and temporal distribution of the canoeists. The observation data of herons' reactions were interlinked with visitor use data to analyse the impacts of recreational use on the avifauna. The distances of flight were influenced by the use levels of canoeists, the habitat quality of the area where herons were observed, and the time of the day. Two-thirds of the interviewed canoeists were not aware of the negative anthropogenic impact on the avifauna.

Variation in life history traits in Bombina bombina from the lower Danube floodplain

Variation in life history traits in Bombina bombina from the lower Danube floodplain