piatok 25. januára 2008

Evolution of meandering lower Morava River (W Slovakia) during the first half of 20th Century.

Pišút, P.: Evolution of meandering lower Morava River (W Slovakia) during the first half of 20th Century. Geomorphologia Slovaca, 2006, 1, 3 figs., 4 tabs., 36 refs., 9 map. refs.

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This paper examines a development of the lower Morava river (Slovak – Austrian stretch) in the time period from 1896 until the river regulation (1951-1962), using historic cadastral maps. Study reach is located between Vysoká p. Morave and Marchegg (river kilometres 16-21). Morphometrical analysis, reconstruction of morphogenesis and morphochronology based on map superposition were aimed to describe channel forms and river planform development over time. Meandering Morava was a dynamic river system here with a continuous bend development at least since 1807. Retreat of outer banks after 1896 averaged 88 m (11-184 m), thus representing mean annual rate of lateral erosion 1.68 m.yr-1 (between 0.6 – 3.2 m dependent on a bend). Despite local channel shortening after a natural meander cutoff around 1906, there was a steady increase in sinuosity of model reach during the studied period, from 2.04 in 1896 to 2.27 in 1950s (present-day channelized Morava is only slightly sinuous river with s2000 = 1.183). The mainchannel development was significantly more dynamic (= narrower channel, minor radii of bends, almost twofold rates of lateral erosion) as of the synchronous evolution of a reference reach at Moravský Sv. Ján (rkm. 62 - 67). Correspondingly, a 100 m wide riverine belt with a soft floodplain woodland site had been forming at Moravský Sv. Ján almost twice as slowly as near Vysoká p. Morave (100 years in comparision to 60 yr). Research findings are of a key importance for predicting future channel changes in the case of Morava restoration by mainflow diversion back into selected cutoff sections.

Z najstaršej prírodnej histórie Mostnej nivy a Auparku

Pišút, P., 2004. From earlier natural history of the Bridge Island and Aupark. Acta Musei Civitatis Bratislavensis, 16, 2004, s. 47-74. In Slovak, English summary, 12 Figs., 1 Tab., 85 references.

The Sad J. Kráľa (Park of J. Kráľ), also known as Aupark, is a green oasis in the very heart of Bratislava. This paper examines the earliest history of this former floodplain, as it is documented by numerous historical maps, written sources and botanical evidence. Demolition of old Petržalka and successive extensive development of this city suburb meant decline for the territory, once favourite recreation place. But we watch in dismay that even now it is increasingly in conflict with plans of modern developers. Some unknown facts from its natural history are presented here, which emphasize its unique geomorphological, biological, historical and cultural values (see also a table, 12 reconstruction maps and ilustrative figures).
After some of the major floods around 1712, a new mid-channel gravel bar appeared in 500 m wide Danube mainchannel between Bratislava (then Pressburg) and the village of Petržalka (Engerau). Soon it developed into a more stable island by vertical accretion and vegetation-growth. Its position made crossing the river easier and safer. Before long, two bridges led to the island, hence its German name Brücken Au, Bruck Auel (= Bridge Island, B. islet). The traffic from
Bratislava across the mainchannel was ensured by a „flying bridge“ (= ferry), whereas fixed bridge led from the island to Petržalka across shallower channel, later known as Höllwasser („Hell´s Water“) or Hellwasser („Clear, light water“). After its destruction by the ice flood in 1740, the wooden pile bridge was re-built into the 270 m long impressive structure. Bank revetment and several groynes were constructed to protect banks and the upstream end of the Bridge Island against floods. Original position of its southern bank where it was in 1751 still indicates a shallow terrain depression in the center of park.
After the construction of the right-side embankment with highway to Vienna in 1770s, Hellwasser channel was cut off and silted up quickly. Eventually, also the 200 m wide Croatian channel (Karlburger Arm) was dammed in 1776-1777. During this period of serio
us human interventions Brücken Au ceased to exist as an island. The original name fell into oblivion and the territory was colloquially referred to as Au, in der Au (= on the floodplain). In 1776, original floodplain forest was adapted into one of the first public parks in Central Europe, which became known as Aupark.
Botanical data presented in this study are mainly based on the work Flora Posoniensis (1791), written by Stephan Lumnitzer. List of 52 species of lower and higher plants reported from the Bridge Island comprises several plants, nowadays completely missing from here, vulnerable or critically endangered. We may also learn quite a lot about the character of local habitats in 1780s, which were either substantially altered or do not exist here any longer. The core of the island represented mature floodplain forest with dominant willows and Black Poplar (Populus nigra). Large areas of sand bars and banks were covered by incipient stages of floodplain forest and by shrub willows, with Purple Willow (Salix purpurea), Osier (S. viminalis), locally with German tamarisc (Myricaria germanica). Dry, elevated, sandy treeless banks were covered by heliophilous herbs. Among local trees, several had already been planted in the late 18th Century, such as the unique Yew (Taxus baccata) and some of sycamores (Platanus occidentalis).
Disastrous ice flood in January 1809 heavily damaged both public park and Vienna embankment. I
t also reactivated the Croatian channel, which became reconnected with the Danube after 31 years of siltation. To May of the same year dates back an earthen embankment, encircling the core of Bridge Island in total lenght of 1 447 m. It was built by Austrian corpses to protect strategical approach to Bratislava against progreding French military. In 1825 repair works at the embankment finally began and at the same time connection with the town was established via permanent bridge of boats. This aided further development of the right riverside (= establishment of Aucafé, Arena theatre etc.). In 1830s, damaged floodplain park was rebuilt into its today´s shape of an English park, which provides light, open views of the entire area.
The Bridge Island played an extraordinary role in life and development of modern Bratislava. This study shows that Aupark is not only public arboretum with renewed or re-built historical buildings, but it also represents a precious fragment of the past landscape with well-preserved natural floodplain landforms (= central terrain depression) and artificial landforms (Napoleonic embankment). This values must not be endangered by any of future decisions which might affect this area.

Príspevok k poznaniu genézy a súčasnej diverzity mäkkých lužných lesov na Žitnom ostrove

Pišút, P., Uherčíková, E., Břízová, E., Hamerlík, L., Čejka, T., 2007. Contribution to the genesis and present-day diversity of softwood floodplain forest at Žitný ostrov Island.

This paper examines alluvial forested swamps of 6 paleomeanders of the former Dudváh river (at Žitný ostrov island, SW Slovakia). Cluster analyses, Twinspan and gradient analysis (DCA) have been adopted to analyse material of 16 phytosoziological relevées and a total of 98 plant species obtained in the course of 2005-2007 seasons. Based on these analyses, examined stands were subdivided into three major groups. First group (2 sites) is represented by poplar monocultures (Populus x canadensis), second (7 sites) by willow – poplar stands with Populus x canescens, Salix alba and S. fragilis and the third one (7 stands) by predominantly willow stands on rather moist sites at the depression bottoms. All examined forests are of secondary origin. They occupy areas of former marshes, which had been partially drained since the early 19th century. Some stands were established naturally, others were intentionally planted for being used as pollard trees. Some species tolerating higher soil salinities (Atriplex prostrata) also occur in the groundlayer vegetation. Today, studied forests represent an important landscape elements in the almost completely deforested agricultural landscape, providing suitable habitats for local flora and fauna. These forest are also valuable as being still free of some common invasive and neophytic tree and plant species (as Negundo aceroides, Aster lanceolatus etc.).

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štvrtok 24. januára 2008

Rekonstrukce vývoje lesní vegetace na Žitném ostrově na základě pylové analýzy

Břízová, E., Pišút, P., Uherčíková, E., 2007. Reconstruction of the forest vegetation development in the Žitný ostrov Island on the basis of pollen analysis.

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This paper summarizes preliminary results of the study focused on geological characteristics, dating and palaeoecological analysis of sedimentary infill of the former Dudváh River palaeomeander. Study area is located in central part of the Žitný ostrov Island, SW Slovakia, near the village Štúrová. Pollen analysis has been carried on a 100 cm thick sediment profile from paleomeander Štúrová. Analyses of 22 samples characterise the development of the water and terrestrial biotope and the surrounding landscape the last ca 2000 – 2500 years. Pollen transported from longer distances was significant due to the openness of the landscape, coming from northern part of Slovakia mountains. A high degree of afforestation (Abies, Fagus, Picea, woods of alluvial forests) was characteristic for the Younger Subatlantic (X). During Subatlantic period, pollen of synanthropic plants appears. Phases of the aquatic and wetland biotope development were defined on the first (DV-SK1) and second (DV-SK2) zones on the basis of coccal green algae and aquatic and wetland plant ecosystems (Myriophyllum, Trapa natans, Potamogeton). The palynological research was supported by the grants (research program) MZP000257801 (Czech Republic) and VEGA 2/5016/25 and 2/5014/25 (Slovakia).

Humér – zaniknutá stredoveká rieka

Pišút, P., 2007. Humér - zaniknutá stredoveká rieka (Humér - disappeared medieval river).

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Before planform simplification, several channels were part of anabranching Danube River on the stretch between Bratislava and Komárno. This paper examines a disappeared medieval channel, reportedly over 30 km long, called Humér (in Hungarian: homorú „hollow, curved“, ér „river channel“). In medieval charters it is evidenced from several places, including the villages of Podunajské Biskupice, 16 km away Lehnice (1313 – 1325), Veľké Blahovo / Vydrany (fluvium Humurus, 1298) and the village of Ohrady (marsh Humoro, 1327). Reconstruction of former palaeochannel is based on historical, toponymical and geomorphological evidence (medieval charters data, 18th-19th century and modern topographical maps, field survey). It was found that at least two different channels of the same name existed at the area in question in the past. First and the most important Humér was a side channel of Malý Dunaj flowing from Podunajské Biskupice across Most n. Ostrove, Tomášov to Janíky. This meandering channel (= sinuosity degree 2.19) was only 20-30 m wide but at least 27 km long and it powered several water mills. It was abandoned some time after 1338. Another Humér was flowing via present-day Miloslavov across Mierovo towards the villages of Sása / Lehnice. Most probably, this branch was inactive as early as 1493 and had no connection with additional records of Humér from distant territories of Veľké Blahovo, Vydrany, Ohrady and Nekyje. Rather, they indicate that toponym homorú could be quite common name of minor meandering streams on the territory of historical Hungary.