17 May 2024

Bridgeman on the roof in Regensburg

The stone bridge of Regensburg is the oldest crossing on the Danube, and the second permanent crossing on the Danube, besides Emperor Trajan's old bridge at Turnu Severin. Its eventful history of nearly nine centuries is full of legends, the most famous of which is the rivalry between the builders of the bridge and the cathedral, which is usually linked to the statue of Bruckmandl on the bridge. This legend probably originated later, the meaning of the statue, like many other figurative representations of the bridge, having been lost centuries ago. Indeed, the statue we see today does not even resemble the version that was damaged earlier. 

The oldest illustration of the Bruckmandl (Georg Hufnagel, 1594. source)

It's quite a coincidence that the statue, known by its many names (Brücken-Männlein, Bruckmandl, Brückenmännchen), still stands on the bridge, defying the centuries. Other similar decorative elements have long since disappeared, collapsed, worn away, dismantled, but the young man with curly hair, sitting on the saddle roof and dressed in a swimming gown, has been restored each time and is still the most photographed work of art by tourists in Regensburg. 

The renovated statue on the stone bridge in Regensburg.

One can only guess who, when and why decided to build this statue. What is certain is that it was placed in its present location after the stone bridge was completed. Regensburg was already an important river crossing before the foundation of the Roman fort Castra Regina in 179 AD, despite the fact that it is a relatively wide stretch of river, dotted with gravel banks and islands. At times, a pontoon bridge could have provided a temporary crossing between the province of Raetia and the Germanic territories, and later between the northern and southern Germanic territories. We have already discussed the changes in the riverbed of the Danube at Regensburg, where we have already described the different conditions prevailing in the riverbed at the time the bridge was built. Presumably, after considerable preparations, such as the accumulation of wood and stone building materials, money and royal approval, work on the riverbed could have begun in the year of our Lord 1135, in an extremely dry, droughty summer, marked by extreme low-water on the Danube, with the foundation of the stone piers.

It took 11 years to build the bridge, opening to the public in 1146, and was hailed as one of the architectural wonders of Europe even at the time of its completion. It is no coincidence that the legend of its construction includes the devil, since it was not at all a natural phenomenon to walk across such a large river, even in the upper, German section, with dry feet in the Middle Ages. The stone bridge was built of sandstone, originally with sixteen piers covering 1/3 of the entire cross-section of the riverbed, which still has a relatively serious backwater effect on the Danube. In the meantime, the bridge has been slightly shortened, with a northern and a southern pier built into the bank. Over the centuries, the piers have been continuously widened by piles and stone deposits, mainly to protect against icy floods. Over time, these piers grew so large that various workshops were built on them, harnessing the energy of the Danube swollen by the bridge piers.

The long gone old towers of the stone bridge (Matthäus Merian)

The decorations and superstructures of the Regensburg stone bridge underlined the political, strategic and economic importance of the structure, as it was much more than a river crossing. Not only did the stone bridge represent the power and wealth of the imperial city to passing merchants, ambassadors and armies, but its construction further enhanced the city's power and wealth by focusing north-south transit traffic to Regensburg. The most striking of the structures were undoubtedly the gate towers. These restricted and controlled the flow of traffic through the city. There were originally three of them, one in the north at Stadtamhof, one at Regensburg (still standing) and one in the middle of the river, on the administrative border between the two towns, roughly where you could get down to the island of Oberer Wöhrd, which belonged to Regensburg. It was this tower that was the first to be destroyed when the city was hit by severe flooding in 1784. The Black Tower of Stadtamhof was damaged during the Napoleonic Wars, when there was heavy fighting on the bridge, and had to be demolished in 1809. 

But medieval travellers would find it difficult to recognise the bridge as we know it today. Over its nearly nine centuries of history, the bridge has gradually lost its decorative elements, its towers and statues, like a Christmas tree that is slowly taken down after the Epiphany. The difference is that the "Christmas tree" in Regensburg has got back a decoration, the Brückmännchen. Some of the ornaments on the bridge are well known, some have been saved in the city museum, while others have been lost forever. 

The third Bruckmandl on a postcard (wikipedia)

There was a basilisk relief on the bridge, on the 10th pillar from the south, on the downstream side, which kept away evil spirits. By this is not meant demons specifically, but e.g. floods and ice and similar harms that threatened the existence of the bridge (=the wealth of the city). Next to it, on the 9th pillar, a weasel was depicted, which, interestingly enough, was able to keep the basilisk in check. This relief, however, had worn off by 1835. Opposite the present statue of the Bruckmandl there was a relief of two fighting roosters, which had a biblical meaning of light and vigilance, but also a secular meaning, perhaps more representative of everyday life in Regensburg: the political struggle between the imperial city of Regensburg and the Duchy of Bavaria, which was separated by the bridge. A statue of a lion, which had lost its head by 1821, stood above the 10th bridge deck from the south. The rest disappeared around 1916/1917. There was also a reclining lion relief on the bridge above pier 11, probably the coat of arms of Emperor Conrad Hohenstaufen. This section of the bridge was blown up by German troops in April 1945, but fortunately it was recovered from the river by divers in 1952 and is now in the city museum. The bridge also featured the coat of arms of the town, the two crossed keys.

Compared to these ornamental elements, the Bruckmandl is a particularly new monument, having spent less than 170 years of its nearly nine-century history in its current location, at the highest point of the bridge, built into its western parapet. The figure himself sits astride the saddle of a superstructure on a massive column, his hands raised to his eyes, looking south towards the cathedral as if to shield his eyes from the scorching sun. This statue was erected on its present site on 23 April 1854, designed by the architect Michael Maurerer, the figure sitting on the roof is the work of the sculptor Anton Blank and has little or nothing to do with the earlier Bruckmandl, to which urban legends are linked.

The city museum has a sandstone sculpture torso with missing arms and legs and a head perched precariously on its neck. It depicts a young man dressed in a loincloth that could pass for a bathing suit. His head is covered with shoulder-length curls, and there are teeth in his half-open mouth. His upper body is turned to the left as he sits on a saddle roof, while a ribbon on the roof is engraved with the Gothic inscription []chuk wie heiß. The front of the inscription is worn away, and the initial letter is presumably an "S". 

Workshops attached to the bridge's piers, the Bruckmandl sits behind the second from the left (source)

The Bruckmandl originally sat on top of the gateway to a hydro-powered grinding mill near the 3rd pier on the east side of the bridge (see initial image) until 1791. By then the plank workshop was gone, and the tower in the middle of the bridge had already been knocked down by the flood of 1784. In 1791, a toll house was built on the site of the tower, which fortunately also had a saddle roof, so the statue was given a new roof to continue looking out over. In 1809 he lost his hands and legs in the Napoleonic wars. Local historiography is typically silent on the fact that most of the damage in Regensburg was probably caused by Bavarian troops allied with Napoleon as they tried to drive the Austrians out of the city. The statue, which must have become unstable during the battle, was knocked onto the bridge by a spring storm in 1817, when the head of the statue broke off. Temporarily repaired, the statue was re-installed on the roof of the tollhouse for a few years, where it continued to withstand the elements until 1826, when the tollhouse was demolished. The Bruckmandl's torso was first taken to the antiquities collection in the cloisters of the cathedral, from there to the Historical Society's collection at the Ulrich Church and then to the city museum. In 1849, on local initiative, a completely new statue was erected in a completely new location, at the highest point of the stone bridge.    

The earliest pictorial representation of the Bruckmandl dates from 1594, Georg Hufnagel's sketch for copper engreving depicts the city of Regensburg from the hills above the Stadtamhof, with a separate enlarged image of the Bruckmandl in the lower left corner. There is a stone gateway with a saddle roof on top. As the structure was part of the eastern parapet of the bridge, the bridgehead faces south, which is the same as the torso in the museum. The inscription 'Schiuck wie hais' is inscribed on the ribbon next to its right leg. However, it is quite certain that this sculpture is not original. This is confirmed by the inscription on the gate: RENOVIERT ANNO 1579, above which is the coat of arms of Regensburg and a date of 1446, presumably the date of construction of the gate, which may have been damaged together with the statue in the fire of 1555.    

Several theories have tried to explain the meaning of Bruckmandl. Some simply saw it as an advertisement for a nearby bath. Such a baths existed in Regensburg, but it is unlikely that the bridge's owner would have allowed such an advertisement to be erected, at least no similar analogy is known. A somewhat more reasonable astronomical theory is that the statue is a direction indicator, an 'angel of the south', showing travellers the direction of south with its dress, its gaze and its hands covering the eyes. This may have been necessary because the stone bridge did not exactly follow the north-south axis, with the northern part of the bridge deviating eastwards and the southern part westwards from the imaginary line. The third theory is relatively modern, and it is about the rivalry between the master mason of the dome and the master builder of the bridge. It is no wonder that the bridge builder won the competition: the construction of the St Peter's Cathedral in Regensburg has begun 127 years after the bridge was opened and was not completed until 1872, when the two towers were also completed in Gothic style.   

Along with the statue, the mysterious inscription has captured the imagination of many people. Some thought that it might refer to the heat and drought that ravaged the area when the bridge was built, but there was also an urban Jewish legend that it was the first words of a mute child thrown into the Danube instead of a fire. A note from a nearby monastery, however, has led to the discovery of a complete version of the text, but it has not been of much help to researchers:

Schuh wie haiß / zu Regensburg seyn dy Heuter feist

The text presumably captures a joke of the time, but its meaning has been lost in the past. At the time of its construction it was understood by everyone, but over time the meaning has faded, but it is similar to the Hungarian saying 'A dead frog croaks on the wet shore of a dry lake': 'It is so hot that I'm freezing,  the horses in Regensburg are so skinny that they are binging'. 

The third version of the Bruckmandl has been restored in 2012-2018 for the last time (source)

There must have been a logical connection between the sculpture and the text, leading many to believe that the saddle roof could represent the skinny horses of Regensburg, although it is likely that in this case there is a much more complex story behind the story. 

Translated with DeepL.com (free version)


  • Karl Bauer: Regensburg. Kunst-Kultur- und Alltagsgeschichte. Buchverlag 2014. 6. kiadás
  • https://www.regensburg.de/kultur/kulturdatenbank/eintrag/118949
  • https://www.regensburger-tagebuch.de/2013/01/das-regensburger-bruckmandl-teil-2.html
  • https://www.regensburger-tagebuch.de/2013/01/das-regensburger-bruckmandl.html#more
  • https://www.bernd-nebel.de/bruecken/index.html?/bruecken/3_bedeutend/regensburg/regensburg.html

27 April 2024

The Castle in the Middle of the Danube


Spielberg castle on the Danube / Litography of Jacob Alt

It's not necessarily the Inség (Hunger) stone at Budapest that comes to mind when talking about rocky islands on the Danube, but rather the Babakai cliff on the Lower-Danube, or Jochenstein on the German-Austrian border. There were also island forts on the Danube, Ada Kaleh was perhaps the finest example, with its ramparts and bastions almost occupying the entire island on which it was built, until it was sunk by the "progression". However, there is another island in the Danube that fulfils both criteria, a rocky promontory and a castle, built in the middle of the Danube. Today, Spielberg's castle is a little difficult to find; it has been moved from the middle of the Danube by river regulation and is hidden in the middle of a riverine forest on the left bank of the Danube at river km 2116, opposite to the town of Enns in Austria.

 Ruins of Spielberg in 1840. (W. Mossman, W.H. Bartlett)

Spielberg castle on Matthias Vischer's engraving, 1674 (source)

Spielberg castle in 1650., sr. Matthäus Merian's engraving (source)

Without the river regulation works, it could be a true castle for hydrologers, ideal for landlords exploring the Danube, as an icebreaker fixed point in the middle of the ever-changing floodplain archipelago between Linz and Mauthausen. On the slower-flowing stretch behind the granite cliff jutting out of the riverbed, gravel bars, sandbanks and islands have formed and transformed after each flood, taking on a new shape. The Danube's turbulent, swirling course over the smaller reefs made navigation in the northern tributary difficult, as did the construction of the castle. 

Originally, Spielberg's granite cliff may have been closer to the right bank of the Danube, as evidenced by the Roman archaeological atrifacts found on it. The legionary camp of LAURIACUM at the mouth of the river Enns, where the veteran Roman soldier St Florian was pushed off the bridge with a millstone around his neck, was situated opposite. The discovery of Roman relics is no less sad a story, as the 1940/41 excavation season was carried out by prisoners from the Gusen concentration camp, a part of the Mauthausen Lager. Prior to that, in the 1930s, in keeping with the spirit of the times, the courtyard of the ruin had been the site of so-called knightly ceremonies held by local Nazis.

The Enns estuary and Spielberg Castle in the middle of the river (drawn by Charles de Feignet)

Spielberg Castle is almost a thousand years old, the earliest part of it dating back to the first decades of the 12th century. It was probably already on an island in the Danube when it was built, as its owners used it primarily as a castle of refuge rather than a residence. In times of war, this impregnable fortress was used by its lords as a refuge for their families, treasures and other valuables. Perhaps that is why its owners treated it like a hot potato, its first half-millennium of history being one of constant changes of ownership. It has been privately owned, owned by ruling families, the Babenbergs, the Habsburgs, and has been owned by various ecclesiastical estates, of which Regensburg was perhaps the most distant, with St Florian's monastery the closest. In 1619 it was a Danube toll-house, but the inhabitants of the castle were fond of plundering Danube sailors shipwrecked on the granite cliffs. Interestingly, the destruction of the castle was not due to siege, fire or frequent changes of ownership, but to the neglect of the longest-standing Weissenwolff family, who owned the castle and later its ruins until 1961. 

The oldest part of the castle is the late Romanesque tower, originally five storeys high, which was added two storeys higher in the early 1500s when the outer castle wall was built. The age of the engravings in the entry can also be determined from the collapsed roof structure in 1840. The best preserved part of the castle is the outer castle. A forester still lives here and carries out basic maintenance work.

The castle on the 1st military survey (1773-1781)

The castle on the 2nd military survey (1809-1818)

The castle on the 3rd military survey (1869-1887)

Parallel to the gradual destruction of the castle in the 18th century, a process was taking place in the Danube riverbed that was slowly removing the castle from the middle of the river. The main riverbed was shifted by the development of the bends to the Enghageni branch, south of the castle, and the 19th century river regulation preserved this situation, which was made worse by the construction of the hydroelectrical power plant between Abwinden and Asten, where the floodplain forest that was home to Spielberg Castle was located directly below the dam, and the drying out of the river had a major impact. The small tributaries forming the archipelago were filled up and the forest covering the different levels of geomorphology grew on the alluvium. To complete this process, Spielberg Castle was officially transferred administratively from Enns to Langenstein on the left bank on 1 January 1997. Spielberg Castle is still privately owned and a local NGO was established in 2013 to maintain and preserve it.

Spielberg castle as it seen today, south from the Gusen bridge (Google)

However, even if they succeed in restoring the castle, the Danube is unlikely to be diverted back to the lonely granite cliff, so the floodplain castle will not again become a unique hydrological curiosity; an island castle on the Danube. 

Translated with DeepL.com (free version)

12 April 2024

The Rise and Fall of the Vienna Archipelago (1529-2010)

Cutting the Gordian Danube, Vienna 1875. (source)

My absolute favourite book of 2023 was Wasser | Stadt | Wien. 458 pages of solid hydrology about Vienna, much of it of course about the Danube. The volume also includes nine full-page pictures of the changes in the river meanders around the city of Vienna. Lovers of urbanism will certainly find things of interest in the previously published images, but it is the floodplain patterns, which are now mainly similar to those of the Danube at Gemenc, Hungary, that are worth observing. It is a little known fact in Hungary that the Danube has caused far more serious problems in Vienna than in Budapest throughout the city's history. In historical times, the Danube flowed through a floodplain up to seven kilometres wide in Vienna, creating and destroying countless islands along this river section. The Viennese had an ambivalent relationship with the river, fearing its difficult crossing between the two banks and the many flood damages, but it was an advantage for the city in terms of trade. Around 1565, the main branch of the Danube moved away from the city and efforts by locals to bring the main shipping route back close to the city failed, leading to a compromise solution of extending the Vienna branch of the Danube, which later became the Donaukanal. 

Ugyanakkor a folyókanyarulatok vándorlása mellett a rendkívül fonatos meder gyakran okozott jégtorlaszokat. A budapestinél sokkal kevésbé stabilabb mederben a zátonyokon és szigetcsúcsokon kialakuló jégdugók gyakran eredményezték azt, hogy a télen levonult jeges árvíz kártételeinek felszámolása után a bécsiek már teljesen máshol találták meg a folyót. Ez az állandóan változó ártéri világ egyre inkább akadályává vált a város terjeszkedésének, amelyre megoldást kellett találni. Végül egy meglehetősen drasztikus beavatkozás szüntette meg a bécsi szigetvilágot 1870-1875 között, amikor is egy új, nyílegyenes medret ástak a Dunának, meghagyva egy széles, hasonlóan egyenes elöntési területet az árvizek számára. Az utóbbi időszak módosításai ezt a területet érintették, amikor a széles, kopár parti sáv helyén létrehozták a Donauinsel-t, melyet a bécsiek már sokkal inkább birtokba vehettek. 1875 után a lefűzött, kiszáradó folyókanyarulatok két utat jártak be. Ahol városi zöldfelületek területére estek, ott javarészt fennmaradtak (Prater, Alte Donau, Lobau, stb.), ahol viszont a város szövete ugrásra készen várta a kiszáradást, ott esetleg csak az utcák nyomvonala emlékeztet a régi medrekre (pl. Schwarze Lacke), többségük több méter feltöltés és beton alatt húzódnak. 

However, in addition to the migration of river meanders, the extremely braided riverbed was often clogged by iceblocks. In a much less stable bed than Budapest's, ice jams on sandbanks and islands often meant that, after the damage caused by the winter ice flood had been cleared up, the Viennese found the river in a completely different place. This ever-changing floodplain world became an increasing obstacle to the expansion of the city, and a solution had to be found. Eventually, a rather drastic intervention eliminated the Danubian archipelago in Vienna between 1870 and 1875, when a new, straight-edged bed was dredged for the Danube, leaving a wide, equally straight floodplain for the floods. More recent modifications to this wide, barren flood area included the creation of the Donauinsel, that was more easily occupied by the Viennese people. After 1875, the story of the newly created oxbows and drying river meanders took two paths. Where they fell into urban green spaces, they were largely preserved (Prater, Alte Donau, Lobau, etc.), but where the urban developers eager for more territory, only the street network may be reminiscent of the old riverbeds (e.g. Schwarze Lacke), most of them beneath several metres of landfill and concrete. 

Half a thousand years of river bend changes in Vienna 1529-2010 (source)

The nine detailed landscape reconstructions created using geographic information methods were almost begging for a .gif version. This version was most certainly created by the authors, but unfortunately the format is not compatible with the capabilities of the Guttenberg Galaxy. So I quickly put together my own version. In varying time-intervals, nine dates in total (1529, 1570, 1662-1683, 1704, 1780, 1825, 1875, 1912 and 2010), we can see the immediate surroundings of Vienna, with the Praterstern roughly in the centre. 

06 February 2024

The Ancient Peninsula of Regensburg

It is a generally accepted view among local historians in Regensburg that the city's islands were formed from an extremely long and extremely narrow peninsula by the catastrophic flood of 1304. This serpentine stretch of land stretched from the mouth of the Naab to Regensburg, i.e. the estuary of the Naab ran parallel to the Danube for about six kilometres. There are, however, some aspects that may call into question the existence of this rare hydrological phenomenon.

I first came across the above illustration on the inside cover of the publication "Regensburg zur Römerzeit", which depicted the hydrological situation shown in the above picture as a fact. According to a brief description of the landscape, the Naab did not flow into the Danube at Mariaort in Roman times, but ran parallel to the Danube for almost six kilometres, passing Kneiting, Winzer, Steinweg and Stadamhof, taking the Regen river on the left bank and flowing into the Danube somewhere at the lower tip of the present-day Unterer Wöhrd, east of Regensburg. In other words, when the second stone bridge was built on the Danube between 1135 and 1146, the famous Steinerne Brücke was still arching over this peninsula to the north bank. The huge peninsula was carved up into four separate islands (Mariaorter Wöhrd, Winzer Wöhrd, and in Regensburg the Lower and Upper Wöhrd) by the catastrophic flood of 23 May 1304. Local vernacular is calling the Danubian islands Wöhrd, which derives from the Middle German word 'werd', while in northern Germany the more familiar sounding form 'Werder' is used.

The "Regensburg Peninsula" already appear in the work of Otto von Freising, who said that the Naab flowed into the Danube at Regensburg. The local chronicler Eberhard von Regensburg is consistent in his description of the events of 1304:
„Anno Domini 1304. Cum aqua Danubii transiens per pontem Ratisponensem omnio versus litus apuilonare declinasset, et litora prope civitatem sicca et arida reliquisset, ceves Ratisponenses artificiose et mulits laboribus et expensis ipsam aquam, ut iterum prope civitatem flueret, ad loca pristina per strues lignorum et congeries lapidum reduxerunt.”
Early medieval hydrographic conditions were already described by the local historians of Regensburg, Plato-Wild (1710-1777), Gemeiner (1726-1823) and Gumpelzhaimer (1766-1841), whose views were later confirmed by detailed research by Adolf Schmetzer. Karl Bauer, in his monumantal local history book (Regensburg - Kunst, Kultur und Alltagsgeschichte), adds to the above theory that at the time of the construction of the Roman legionary camp Castra Regina (A.D. 180), a change in the riverbed probably caused the Unterer Wöhrd to form a separate island. At Bauer, the date of the flood disaster was two days later, 25 May 1304. On that date, the Danube between Winzer and Pfaffenstein broke through the Regensburg Peninsula and the main riverbed was moved into the old bed of the Naab between the present-day Oberer Wöhrd and Stadtamhof. According to some local oral traditions, the northern branch of the Danube was still called the Naab around 1915.

The section of the Danube between the Naab and the Regen in 1829 (source)

The result was that the free imperial city of Regensburg lost its Danube port, its customs revenue, its mills ran dry, all of which threatened the city's economical power. As the city was in frequent dispute with the town of Stadt am Hof, on the other side of the old Naab, under the jurisdiction of the Bavarian prince-elector, the locals had to act very quickly. It is not clear whether in the same year or in the summer of 1305, during a very dry period when it was possible to cross the shallow Danube, a water control structure called Wöhrloch was built at the top of the Oberer Wöhrd, which was intended to both return most of the Danube's discharge to its original course and leave some (border) water between the Regensburg-owned Oberer Wöhrd and the neighbouring Stadamhof. The Wöhrloch, consisting of a combination lock and weir, was, like the stone bridge, a marvel of engineering on such a grand and rapid scale. However, for centuries it was the source of strife between the city of Regensburg and the Bavarian prince-elector, who wanted to widen the basin to allow larger ships to enter Stadtamhof, boosting trade. Disputes over water management sometimes led to the Wöhrloch being destroyed by the military.

The Wöhrloch in 1638 (source)

In addition to the historical plot, which is worthy of Ken Follett's 'Pillars of the Earth', the question arises: can such an unstable formation be created hydrologically on a river with such a variable flow over such a long period of time? Although the historical sources are clearly "pro-peninsula", there are some hydrological factors that may call into question its existence and its persistence over many centuries.
  • The Danube reaches its most northerly point at Regensburg, where it makes an almost right-angled bend at Winzer, changing from a northeasterly to a southeasterly course. There is also a bend with similar parameters just above the mouth of the Naab, both of which have in common that they head towards a steep hillside. The development of the bend in the river has therefore washed the left bank year after year, and has thinned the peninsula most in the vicinity of Winzer, which is consistent with what historians say about the site of the 1304 breach. 
  • The parameters of the peninsula also suggest that it was not very stable: it was 6 km long from the mouth of the Naab to Regensburg and probably 100 m wide at most. If we take the distance between the Roman castellum of Großprüfening and the hillside above Mariaort, the peninsula was located in a river floodplain cross-section of up to 600 metres in width. In such a section, major floods have had the opportunity to breach the floodplain several times over a period of 1200 years.
  • The only permanent watercourse between the Naab and the Regen is on the left bank, the Brückelgraben. This is a relatively short stream with a low discharge, but it probably built up a cone of sediment in the Danube (or earlier in the Naab bed) from the alluvium carried by the hillside area during major rainfalls, forcing the river of the northern branch southwards, which may ultimately have caused the gradual thinning of the land mass. 
Based on the sources, it seems more likely that the Danube's longest peninsula did exist, but reconstructing exactly how long and how its gradual thinning took place would deserve further research.

Sources and literature:

05 January 2024

L'ouverture du Rollerdamm



Le 30 mai 1875, en présence de Sa Majesté François-Joseph Ier, empereur d'Autriche et roi de Hongrie, le Danube fut inauguré à Vienne lors d'une cérémonie dans son nouveau lit rectiligne et canalisé. Le 15 avril, un mois et demi avant la cérémonie d'inauguration, la digue de protection en terre (Rollerdamm) fut ouverte et le Danube entra dans son nouveau lit canalisé juste au-dessous du pont des chemins de fer du Nord-Ouest (Nordwestbahnbrücke). Trois jours plus tard, le premier bateau à vapeur franchissait déjà le nouveau tronçon. L'histoire de la Rollerdamm est reconstituée ci-dessous sur la base des écrits du livre Wasser | Stadt | Wien.

La digue de protection en terre (Rollerdamm) à Vienne le 10 avril. 1875. (Image originale)

À Vienne, le Danube était déjà un fleuve relativement régulé avant le début des grands travaux de régulation en 1870, malgré les méandres naturels qui subsistaient. La quasi-totalité des berges du lit principal avait été stabilisée en 1869 sur la base d'une planification locale ou centrale. Cependant, le lit principal, stabilisé par des épis, des blocs de pierre et des pieux, était encore trop large, créant un potentiel pour la formation de nouveaux bancs de graviers, comme dans le Gänsehaufen près du port de Kaisermühlen. À cette époque, les travaux de régularisation étaient encore principalement destinés à la navigation, la protection contre les inondations n'étant qu'une préoccupation secondaire. Lorsqu'en 1862, une embâcle inonda les faubourgs de Vienne, le gouvernement monarchique créa une commission de régulation du Danube, qui ne put commencer ses travaux qu'après la guerre perdue avec la Prusse en 1867. Les membres de la commission (ingénieurs, administrateurs et experts en navigation, chemins de fer) se partagèrent rapidement autour de deux positions très divergentes. Le groupe de Pasetti était en faveur d'un redressement du lit principal existant, tandis que l'autre groupe plaidait pour un nouveau lit unique et canalisé. La question est restée longtemps dans l'impasse et a finalement été tranchée par le retrait de Pasetti au profit des partisans de la version canalisée. Ce plan était principalement soutenu par les défenseurs du commerce et des transports.

L'entreprise française "Castor, Couvreux et Hersent", qui avait déjà fait ses preuves sur le canal de Suez, s'est vu attribuer le contrat. Le tracé du nouveau canal en courbe, établi en 1868, comportait trois points fixes : l'affleurement près de Nußdorf, le pilier récemment érigé de l'Ostbahnbrücke près de Stadlau et la section de la digue déjà achevée au niveau de la Lobau. Ce plan nécessitait deux grandes coupes sous et au-dessus de l'Ostbahnbrücke. L'entaille supérieure avait une longueur de 6 640 m, l'entaille inférieure une longueur de 2 550 m, et une zone d'inondation stérile de 475 m de large (Inundationsgebiet) devait être créée sur la rive gauche pour évacuer l'excédent d'eau des crues.

La position du Rollerdamm (source)

La section inférieure du nouveau Danube près de Freudenau à Weidenhaufen a été réalisée par la construction d'un fossé de 114 à 170 mètres de large, qui a ensuite été élargi par le Danube, emportant la plupart des sédiments vers le Marchfeld. La partie supérieure avait été entièrement excavée, mais lorsque le nouveau lit de la rivière fut dragué près de Nußdorf, les ouvriers eurent une mauvaise surprise : le lit de la rivière était jonché des restes de travaux d'ingénierie fluviale des siècles précédents. Pendant des années, les dragues à vapeur se sont efforcées de les dégager, mais les machines utilisées à l'époque étaient trop faibles pour enlever ces défenses massives. Au total, des milliers de pieux en bois datant de plusieurs siècles et 18 kilomètres et demi de structures en bois diverses furent retirés.

Pour la construction du canal, les dragues à vapeur et les transporteurs ont été utilisés pour la première fois à grande échelle et ont dû déplacer une quantité incroyable de sédiments pour l'époque. La plupart des 16,4 millions de mètres cubes de sédiments, de gravier et de sable excavés ont été utilisés pour remplir les zones suburbaines de Brigittenau et de Leopoldstadt, contribuant ainsi grandement à l'augmentation de la zone urbaine de Vienne. Le nouveau lit du Danube à Vienne comprenait la construction de digues de protection contre les inondations des deux côtés, l'approfondissement du canal du Danube et la construction de cinq nouveaux ponts sur le Danube.

Lors du dragage du nouveau lit, une étroite digue de terre appelée "Rollerdamm" a été laissée dans la partie la plus septentrionale du lit, maintenant jusqu'au dernier moment la direction de l'écoulement vers l'Alte Donau. À l'origine, cette digue n'était pas perpendiculaire au nouveau lit de la rivière, mais suivait la ligne d'écoulement de l'Alte Donau depuis la rive gauche des ponts actuels de Florisdorf jusqu'au Handelskai sur la droite. Il était également surmonté d'un chemin de fer industriel, dont l'un des terminaux se trouvait sur l'actuelle Friedrich-Engels-Platz. Le 15 avril 1875, un mois et demi avant la cérémonie d'ouverture officielle, le Rollerdamm a été ouvert sous la direction du géologue Eduard Suess, la petite brèche étant rapidement élargie par le Danube jusqu'à ce que le barrage soit complètement emporté sur la largeur du nouveau lit du fleuve.

Dans un premier temps, le Danube s'est montré réticent à occuper le nouveau lit. Après le retrait des crues de printemps, la fermeture technique de l'Alte Donau a commencé, mais dans le lit rétréci, le fleuve exerçait encore une force considérable, déplaçant les bateaux chargés de pierres enfoncés dans le lit, détruisant la digue en cours de construction et creusant de profondes fosses dans les sédiments meubles. Finalement, des structures en bois remplies de blocs rocheux ont été reliées entre elles par des câbles et mises en place sur des voies ferrées, fermant définitivement l'ancien lit de la rivière. Peu de temps après, en février 1876, le premier "test de résistance" du nouveau système d'approvisionnement en eau de Vienne a été effectué. Dans le tronçon du Danube encore non régulé de Vienne, sous le pont Ostbahnbrücke à Stadlau, la glace s'entassa et l'eau en crue, repoussée par le barrage de glace, trouva son exutoire dans le bras mort de l'Alte Donau. La digue inférieure et la digue supérieure se rompirent et les trente-trois bateaux de la compagnie "Castor, Couvreux et Hersent" furent emportés hors de l'ancien bras et mis à terre, endommagés, dans une prairie fluviale près de Fischamend. Le 25 février 1876, le London Times a également fit état de la prétendue défaillance totale des ouvrages de régulation à Vienne et publia une fausse nouvelle selon laquelle le nouveau cimetière central de Vienne était tellement inondé que les cadavres avaient été emportés hors de leurs tombes.

L'ouverture du Rollerdamm le 15 avril 1875.
Au-delà se trouve le pont du chemin de fer du Nord-Ouest, construit en 1872. (source)

Après la fermeture du Vieux Danube (Alte Donau), de vastes étendues de champs de graviers furent laissées à sec. La zone a rapidement été envahie par les baigneurs viennois. En leur faveur, les autorités ont dragué le bras mort pour améliorer la qualité de l'eau, ce qui a finalement permis à cette zone humide urbaine de survivre. En raison de la régulation du Danube à Vienne, le niveau de la nappe phréatique s'est abaissé de 1,3 mètre en moyenne, de sorte que la valeur immobilière de la plaine inondable du Danube a fortement augmenté parallèlement à celle des décharges. La disparition des méandres naturels, la formation d'îles et de bancs de graviers et l'arrêt de leur migration ont finalement conduit à l'urbanisation rapide des berges et, parallèlement, à la dégradation et à la disparition rapides des habitats naturels.

Traduit par deepl.com et Eric Baude (http://www.danube-culture.org/).

Opening the Rollerdamm



On 30 May 1875, in the presence of His Majesty Franz Joseph I, Emperor of Austria and King of Hungary, the Danube in Vienna was inaugurated with a ceremony in its new, straight, canalised riverbed. On 15 April, a month and a half before the inauguration ceremony, they opened the Rollerdamm and the Danube entered into its new channel just under the Nordwestbahnbrücke. Three days later, the first steamship was already crossing the new stretch. The below history of the Rollerdamm is reconstructed on the basis of the writings of the book Wasser | Stadt | Wien.

The Rollerdamm in Vienna on April 10. 1875. (Original image)

In Vienna, the Danube was already a relatively regulated river before the start of the Great Regulation Works in 1870, despite its remaining natural meanders. Almost the entire banks of the main riverbed had been stabilised by 1869 on the basis of some local or central plannning. However, the main bed, stabilised with groynes, stone boulders and piles, was still too wide, creating the potential for further gravel bar formation, such as in the Gänsehaufen near the port of Kaisermühlen. At that time, regulation works were still primarily for the benefit of navigation, flood protection being only a secondary concern. When an icy flood in 1862 inundated the lower suburbs of Vienna, the Monarchy's government set up a Danube regulation commission, which could only begin its work after the lost war with Prussia in 1867. Members of the committee (engineers, administrators and shipping, railways experts) soon began to group around two widely divergent positions. The Pasetti group was in favour of a straightening of the existing main riverbed, while the other group argued for a new, single, channelised riverbed. There was a long stalemate on the issue, which was finally settled by Pasetti's withdrawal in favour of the supporters of the chanellized version. This plan was mainly supported by trade and transport advocates.

The French company "Castor, Couvreux et Hersent", which has already proved its worth in the Suez Canal, was awarded the contract. The route of the new, curved canal, which was laid out in 1868, had three fixed points: the outcropping near Nußdorf, the recently erected pillar of the Ostbahnbrücke near Stadlau and the section of the already completed dyke at Lobau. This plan required two major cuts under and above the Ostbahnbrücke. The upper cut was 6640 m long, the lower one 2550 m long, and a barren 475 m wide inundation area (Inundationsgebiet) was planned to be created on the left bank to drain off the excess flood water.

The position of the Rollerdamm (source)

The lower section of the new Danube near Freudenau at Weidenhaufen was done by the construction of a 114-170 metre wide ditch, which was then widened further by the Danube, washing out most of the sediment towards the Marchfeld. The upper section had been fully excavated, but when the new riverbed was dredged near Nußdorf, the workers were in for a nasty surprise: the riverbed was littered with the remains of river engineering works from previous centuries. For years, steam dredgers had struggled to dredge them out, but the machines used at the time were too weak to remove the massive defences. In all, thousands of wooden piles from different centuries and 18 and a half kilometres of various wooden structures were dredged out.

To build the canal, the steam dredgers and transporters were used for the first time on a mass scale had to move an incredible amount of sediment for the time. Most of the 16.4 million cubic metres of sediments, gravel and sand excavated were used to fill the suburban areas of Brigittenau and Leopoldstadt, contributing greatly to the increase in the urban area of Vienna. The new Danube riverbed in Vienna included the construction of flood protection embankments on both sides, the deepening of the Danube canal and the construction of five new bridges over the Danube.

During the dredging of the new riverbed, a narrow earth dike called the "Rollerdamm" was left in the northernmost part of the riverbed, maintaining the flow direction towards the Alte Donau until the very last moment. It was not originally perpendicular to the new riverbed, but followed the flow line of the Alte Donau from the left bank of the present-day Florisdorf bridges to the Handelskai on the right. It also had an industrial railway on top, one of its terminal was at today's Friedrich-Engels-Platz. On 15 April 1875, one and a half months before the official opening ceremony, the Rollerdamm was opened under the direction of geologist Eduard Suess, the small gap being rapidly widened by the Danube until the dam was completely washed away along the width of the new riverbed.

At first, the Danube was reluctant to occupy the new riverbed. After the spring floods receded, the technical closure of the Alte Donau began, but in the narrowing bed the river still exerted considerable force, displacing stone-laden boats sunk into the bed, destroying the embankment under construction and carving deep pits in the loose sediment. Finally, wooden structures filled with boulders were wired together and lowered into place on railway tracks, permanently closing the old riverbed. Relatively soon afterwards, in February 1876, the first "stress test" of the new Vienna water system was carried out.  In the still unregulated Danube section of Vienna, under the Ostbahnbrücke in Stadlau, the ice was piled up and the raising water, pushed back by the ice dam, found its outlet in the Alte Donau oxbow. Both the lower and upper embankment broke and the thirty-three ships of the company "Castor, Couvreux et Hersent" were washed out of the old branch and put ashore, damaging them, in a riverine meadow near Fischamend. On 25 February 1876, the London Times also reported on the alleged total failure of the regulation works in Vienna, and published the fake news that the new central cemetery in Vienna was so flooded that dead bodies had been washed from their graves. 

The opening of the Rollerdamm on 15 April 1875.
Beyond is the Nordwestbahnbrücke, constructed in 1872. (source)

After closing the Alte Donau, large stretches of gravel fields were left dry. The area was soon swarmed by bathers from Vienna. In their favor authorities dredged the oxbow to improve water quality, which ultimately led to the survival of this urban wetland. As a result of the Danube regulation in Vienna, the groundwater level has sunk by an average of 1.3 metres, so that the real estate value of the Danube floodplain has increased greatly in parallel with the landfills. The loss of natural meander development, the formation of islands and gravel bars and the cessation of their migration ultimately led to the rapid urban development of river banks and, in parallel, to the rapid degradation and disappearance of natural habitats.

19 December 2023

Ada Kaleh buried by Danubian sediments

It's been more than fifty years since the island of Ada Kaleh, with its adventurous past, monuments and fort, was buried under the Danube after the construction of the Iron Gate I hydroelectrical power plant. Since then, it has been lost to sight, sleeping in its eternal slumber at a depth of about 30 metres. But a recently discovered sonar image gives us a rough idea of the decades the island has spent in the depths, and also reveals that, contrary to legend, the tower of the Turkish minaret will no longer emerge, even if the reservoir level drops.

Ada Kaleh in a watery grave (source

In the first days of December, Ada Kaleh's underwater sonar image was posted on several Facebook groups. However, the post, which included a source tag and information on the image, was later deleted, but by then the image had been downloaded. The image was also published in the Romanian media on 13 December, but aktual24.ro only reported the story of the island and the imaging process in a paragraph. According to this article, the image was taken with a multibeam echosounder (MBES) at an unknown time. The MBES is based on a sonar mounted on a floating structure, which emits sound waves in the direction of the seabed in the shape of a fan and calculates the distance from the reflection time. The sound waves from Ada Kaleh's deep-hidden ramparts and buildings return sooner because they are closer to the surface than the deeper forms of the Danube bed. The distance data are represented by a colour scale, where blue represents deep and red shallow. Unfortunately, the image does not provide any specific data in the form of a legend.

The sonar image shows only the western part of Ada Kaleh, lying like a wreck in the Danube. The sparsely built-up garden area to the east has been left out, probably because the survey was limited to a small area. It is worth comparing with the sketch of the island as a whole. The two-street settlement itself was located within the inner ramparts. In addition, there was an outer wall system, but the western tip of the island was also fortified with bastions with eaves in the mid-18th century. The Turkish settlement also included a mosque with a slender minaret expanding from it, which stood roughly in the middle of the island, above the eastern gate. If it is true that the fortress was demolished by the Romanian state before the flooding to build a replica of the bastions from the bricks on Simian Island, relatively minimal work was done, as the fortress walls are still sharply defined in the sonar image. Although the sketch does not show the topography, contemporary photographs or postcards show that the moat system between the outer and inner ramparts was standing water, while a small forested island grew in the southern inner curve of Ada Kaleh.

A sketch of the island before the flooding

From a hydrological point of view, the sonar image can be described as extraordinary. It contains extremely important information about the sedimentation processes that took place after the flooding. So far, the blog has published two large-scale articles on the sedimentation of the Iron Gates, one on the three towers of Trikule and the other on the Crown Chapel near Orsova, which illustrated the process of filling in the section of the river that was backwatered by the Iron Gate I power plant. The same can be done for the island of Ada Kaleh, where the sonar image gives a very detailed picture of the altered flow conditions and the associated sediment movements.

Farewell. Soon the ramparts will be swallowed by the Danube reservoir.

Let's take a look at the sonar image, especially the longitudinal positive shape extending to the right of the fortress. At first glance it looks like a long dune in the desert. Several similar forms can be observed within the fort area and in the western foreground. All of them take the same direction and are characterised by being 'lee shaded', i.e. they are formed behind a large projecting wall section or bastion. They do not follow the course of the Danube branches that surrounded the island of Ada Kaleh from two directions, but appear to run straight through the longitudinal axis of the island. It is also revealing that, apart from the ramparts and one or two houses, the settlement's street network is not visible. One reason for this is that the Romanian state has done a thorough job of systematically destroying the houses of the Turks, extracting as much building material as possible. Another is the aforementioned filling of the reservoir.

Once the island was submerged, the flow conditions changed fundamentally. The drift lines that had been bypassing the island in two directions merged just above the island, as evidenced by the direction of the sediment plumes. As Ada Kaleh remains in the centre line of the estuary, unaffected by the construction of the streamside alluvial cone, the sediment deposited in the fort moves in the direction of the Iron Gates dam in the centre line of the estuary. Where the water flow encounters an obstacle, such as along the line of the ramparts, it first deepens the bed by breaking through the obstacle and deposits the sediment washed out in quieter areas such as the western foreshore, the interior of the fort, or even the eastern extension of the island. The sonar image shows that the most significant erosion is at the base of the wall of the fort in the south-west corner of the island. This outcrop probably formed a significant depression in the riverbed before the flooding.

This suggests that the sediment conditions of the former island are not primarily determined by the sediment that is being deposited from the filling reservoir, but by the sediment that is being washed locally due to the changed flow conditions in the bed, and to a lesser extent by the trapping of transported sediment from further away. And it is the demonstration of this that gives the sonar image its importance, and we can only hope that measurements will be taken at regular intervals so that the data can be compared and possible trends in sediment accumulation and leaching can be identified, preferably for the whole island.

26 October 2023

Three Sentences on Haynau


True, it has nothing to do with that Haynau, born in Kassel, Germany, but there was an island of that name on the Austrian section of the Danube, namely west of the castle of Wallsee, roughly opposite Mitterau/Ledererhaufen, which was nominated in the 2023 Danube Island of the Year vote.

Haynau on the Danube (mapire.eu)

Now that the 150 years have passed and it is safe to write about this island, which originally belonged to Upper Austria, it is worth mentioning first that Haynau (also known as Hain Au, or, in English, a Danubian sandbank with groves) is, like many of its Austrian Au counterparts, a young landform, because, like the Gemenc region in Hungary, islands and reefs on this originally braided stretch of river were very often born, disappeared or transformed.

Haynau was formerly part of a larger river bend, Grünau, in the south, and only later became an 'independent' island, sometime in the 1870s, as it first appears on the sections of the 3rd military survey, while its present form as a tied peninsula is due to the Wallsee-Mitterkirchen hydroelectric power station, built between 1965 and 1968, which eventually connected it to the Lower Austrian riverside.

14 October 2023

Royal Oaks of Vének

The Csallóköz (Žitný ostrov) is typically referred to as the Golden Garden in the Hungarian literature. Exactly why this is so, perhaps because of the gold panning, will probably never be known, but it is certain that a piece of the "Golden Garden" can be found on the opposite side of the Danube, the Szigetköz, near the village of Vének. Twelve oaks form this Golden Garden, each are older than a hundred years.  

Royal oaks of queen consort Elisabeth

It's not a big garden, with just a dozen oak trees, plus the meadows underneath. It looks like an extension of the village built on a narrow river bank. Along the huge flood protection embankment that runs alongside it, trees have been felled, but at this point the rule seems to be broken. Less noticeable on the site, but the trees are planted in regular order, assessing from their size a long time ago. Unfortunately, one of them, judging by the withered leaves on one of its branches, has dried up this year. The information plaques under the oaks date their age to at least 125-127 years, since the saplings were planted in two phases; in 1896 and 1898, first to commemorate the Hungarian Millennium and then two years later to commemorate the death of queen consort Elizabeth (10 September 1898), Franz Josef's wife. The former group forms a hexagon, with the famous Árpád oak in the middle, underneath which the villagers hid a time capsule. The south-eastern part of this group of trees dried up this year, breaking the geometric shape. Five of the Elizabeth trees form the letter "X", west of the Millennium group. These shapes can be seen really well from above in the leafless season. The conservation value of this group of trees is that the saplings are said to have originated from the now deforested hardwood groves of the Szigetköz.

The golden garden in gray scale. (fentrol.hu) 1969. november 12.

It didn't take much for the Hungarian Water Authority to cut these oaks down for flood protection reasons. According to press reports of the time, the oak grove was saved thanks to József Pados, the last school principal in Vének, who "formed a human chain around the grove with his primary school pupils, which made the people with chainsaws and their bosses, who were marching to the storage area, back off": 

We escape the heartbreaking silence of the school. József Pados knows an interesting story about every house in Vének. We go from gate to gate, and old stories and mischiefs warm up in his memory. At the end of the village we stop in front of the Golden Garden. Beautiful oaks sway their branches in the warm wind. 

- This is the tree of the seven chiefs. They were planted at the Millennium. According to the writings that have come down to us, the names of the people of the village at the time were placed in a jar at the base of the Árpád tree, and one of each of the coins of the time was also placed at the base of the tree. 

- These were the trees you even called me to save? 

- Yes. They were going to be cut down years ago because there is a regulation that there can be nothing on the ground within sixty metres of the side of the embankment. Fortunately, they were rescued. I did a lot of research, but my efforts were not in vain. Now, not only the inhabitants of Vének, but also the people of Győr can enjoy it, because more and more small weekend houses are being built on the banks of the Danube. Kolerasziget, Tordasziget, Angliakert, Szélkert, Ficsor-dűlő, Rókadomb, Ciglés, Ökörmező - you know the history of all of them and you know the area like the back of your hand.

The trees of the Golden Garden have been saved and have been protected since 1982. The school was not so fortunate, the children from Vének are now taken to school in Kisbajcs.

Resting St John of Nepomuk

Despite the fact that one of the millennium oaks has withered, there are still a dozen trees defying water regulations, as an old black poplar tree stands on the side of the embankment north of the oaks, sheltering the statue of St John of Nepomuk, who rests beneath it. It watches the traffic of at least three dusty roads, while the Danube flows behind it, beyond the embankment.