Neither Crayfish Nor Water

MAGYARUL

however in principle, both would be required to name an old branch of the Danube in Vienna Krebsenwasser. If neither exists anymore, it might be better to call it Unteres Heustadlwasser, as these two bodies of water formed a common riverbed in the Prater before the great Danube regulation. 

What is this all about? There is a world of difference between the appearance of the Danube in Vienna before and after 1875. Until the river was regulated, the Vienna section of the river was constantly changing and and transforming landscape, very conducive to the formation of islands and gravel bars, where no distinct main channel could develop, where the Viennese had to fight a constant battle with the river, which changed its course from year to year, and where communication between the right and left banks was rather difficult. The ancestor of the Krebsenwasser, the Heustadl-Danube, was once a main branch of the Vienna Danube, which began to migrate towards the right bank, the city, in the early 1600s, reaching its greatest width at the beginning of the 18th century. Its meandering broke through the tree-lined avenue leading to the Lusthaus and between 1704 and 1713 threatened to break through into the Vienna branch, which was the predecessor of today's Donaukanal. This catastrophe was averted by closing the Heustadl-Danube, but as a result, this branch gradually withered away during the century and was only one of many tributaries when it was finally closed off from the main branch in 1875. 

The separation of the Krebsenwasser and the Heustadlwasser after 1875. (mapire.eu)

A total of four former branches of the Danube remained in Vienna's Prater after the radical river regulation intervention of 1875, when one of the largest island destruction in the history of the Danube took place. Of the remaining branches, we have already visited the Lusthauswasser and the upper branch of the Heustadlwasser. The elimination of the Viennese archipelago with a single straight channel allowed the city to begin its expansion into the floodplain areas at the expense of the Danube's labyrinth of riverbeds, shoals, and islands. 

Where are we, what do we see? The shrinking Hesutadlwasser and the Vienna Prater. (source)

Since the Prater has long functioned as Vienna's city park, development here has been largely restricted by nature conservation considerations, and certain open water sections have been preserved, but one of Europe's busiest transport routes, the eight-lane A23 motorway, was nevertheless built here in 1978.

The lower part of the Prater and the new section of the Donaukanal. (source)

As far as the motorway is concerned, at least they took into account that it was built as a bridge over the dense, wooded area, but it is still not the classic canopy walkway that would normally be built in such a place. Due to lack of space in Vienna and other large cities, infrastructure investments are often constructed at the expense of remaining natural habitats, such as in the case of the new Vienna transport corridor planned through the Lobau floodplain on the left bank. If we look only at the Krebsenwasser without the Upper Heustadlwasser, here too two roads have further fragmented the remaining Danube backwater. The first is the Aspernallee, which runs from the Praterkai railway station to the east of the Haustadlwasser and Krebsenwasser break, arriving at the Lusthaus' star from the northeast. Road traffic runs along this road, and a narrow culvert at the intersection provides a connection between the two parts of the riverbed. To the east of the Maria Grün Catholic Church, which is used by Croatians living in Vienna, a narrow embankment leads across the riverbed, under which there is also a culvert built of concrete rings, but on this road only a forest path used by hikers leads to Dammhaufengasse. In addition, another path crosses the riverbed where the forest opens up slightly and gives way to reeds, indicating that the time has not yet come for woody plants to take over this depression.

The Krebsenwasser from the Aspernallee.

Embankment across the old riverbed, towards the Dammhaufengasse.

The remaining treeless riverbed.

The Krebsenwasser in morning sunshine, across.

The Krebsenwasser in morning sunshine, along.

The remaining water with an out-of-order gauge.

The esastern end of the Krebsenwasser.

The living and the dead.

On October 28, 2025, there was only a little water in the deepest part of the Krebsenwasser, mostly hidden from curious eyes by reeds. Hopefully, if there are any remaining specimens of the eponymous crayfish, they can hide here, waiting for rainier times. The only water gauge in the 30-meter-wide and 300-meter-long section of the riverbed was dry at this time. 

In the wooded section towards Aspernallee, the morphology of the riverbed was recognizable, but its vegetation was no different from that of the surrounding, higher-lying forest areas. The soil was somewhat softer and wetter, but there was no sign of surface water, nor was there anything to suggest its presence. The deeper part of the Krebsenwasser is probably only replenished by groundwater and precipitation, which can be sucked up through the gravel bed by the low water level of the current main branch flowing just 200 meters away.

The water shortage, drying up of backwaters, and reforestation observed in the case of Krebsenwasser can be seen not only in the Prater, but also in the Lobau area on the opposite bank. This is a natural process (after the anthropogenic Danube regulation), as in the absence of water flow (flooding in the Prater is practically impossible nowadays), dust, leaves, rubbish, etc. that fall into the water cannot be washed away. However, this process can be faster or slower, depending on the precipitation and groundwater conditions in the area. The year 2025 will go down in hydrological history due to its exceptionally low water levels, and this situation is also reflected in the case of Krebsenwasser during the autumn low water period.

Here, too, there is nothing left to do but to document the final drying up. 

Translated with DeepL.com (free version)

Riverside Maria and the Fall of Vindobona

MAGYARUL

There are "speaking" geographical names along the Danube, sometimes in the most unexpected places, often far from the river, such as one of Vienna's oldest churches. The German name of the Gothic church of Maria am Gestade clearly indicates that it stood on the riverbank when it was built, but today it is several streets and 320 metres away from the Donaukanal. The evocative name of the former church of the Danubian boatmen takes us back to the ancient history of Vienna's urban waterways and explains the peculiar shape of Vindobona's late Roman legionary camp.

The idealized image of the castra Vindobona before the III. century (source)

42 steps. That's how many steps you have to climb to get from Salzgries Street to the Roman Catholic Church of St Mary of the Riverside, on Passauer Platz, named after the former owner of Bishopric of Passau. But there are just as many steps for those arriving from the Tiefer Graben (Deep Trench - another "speaking" geographical name!), but probably even more for the medieval boatmen who climbed up from the Danube harbour below the bank to the church on the high bank, since the landfills that has since been done has reduced the difference in level considerably over the centuries. This high bank, marked by steps, can be followed eastwards to Schwedenplatz, and the site of Vienna's oldest church, the Ruprechtskirche, legend has it that it was founded in 740. The riverside Church of St. Mary and the medieval city wall immediately adjacent to it have dominated the Danube landscape of Vienna for centuries, initially the wooden chapel, then the stone church rebuilt in Gothic style at the turn of the 14th and 15th centuries, and its 56-meter-high tower, which was already raised by another 15-meter of the higher ground. 

42 steps of the Marienstiege towards the Passauer Platz.

The right bank of the Danube in Vienna can generally be compared to a flatter Greek theatre, where the surface slopes gradually and arena-like towards the Danube. At the end of the Last Glacial Maximum, this slope was even less uniform, with flatter surfaces alternating with steeper slopes, as if they were terraces. This stepped, terraced pattern was formed by the changing water flow of the Danube during the Ice Age, mainly for climatic and tectonic reasons, and the gravel material of the higher terraces was also covered by loess layers during the late Ice Age. However, since their formation, these terrace generations have been gradually exposed to the very strong lateral erosion of the Danube, caused by the local braided, anastomosing bedforms of the Danube. Vienna's urban core was also created on one such flood-free Danube terrace, the youngest, namely on the so-called Prater Terrace. The Prater terrace was formed during the Würm glaciation, and its gravel was deposited in Vienna at an altitude of 145-153 metres above sea level.

Danubian Terraces of Vienna. The Prater Terrace is nr. 6 with lilac color. (source)

The Roman military engineers had a fairly good sense for choosing camp sites, typically settling along river crossings, on flood-free ground, at road crossings, in well-protected areas and near fresh water sources. In Vienna, too, they built as close to the river as possible, where, after the conquest of the province of Pannonia, the Roman Empire built an earth-wood military camp for its auxiliaries on the flood-free Prater Terrace. In the case of Vindobona, crossing the Danube was somewhat problematic, as the floodplain reached a width of 6-10 kilometers and dotted with islands and gravel bars, and often had no specific main branch. The Romans chose the Danube estuary of the Ottakringer stream, nowadays known mainly for the yellow-labeled beer, which cut deep into the loess surface, as the military base, following the erosion valley of the Tiefer Graben, providing a natural moat for the military camp of Vindobona. There was also a good reason why the fortress was not built on the banks of the Wienfluss: the marly rock and soil conditions of the Wiener Wald mean that rainfall can only drain away to a limited extent, so at major rainfalls discharge often increased to devastating floods towards the Danube, and the cone of alluvium deposited in the riverbed not only impeded navigation but also had a profound effect on the development of the bends in the Danube branches on the right bank.

Cross section of the Danubian Terraces. Lilac: landfill, gray: loess, green: terrace gravel (source)

At the turn of the 1st and 2nd centuries the standard and regular Roman legionary camp was built, with a standard layout, familiar from many places along the Danube, but it is important to note that the orientation of the camps was not always aligned with the cardinal points, at Vindobona there is a 45 degree angle of deviation, i.e. the sides of the camp do not give the cardinal points, but the corners. Within the walls, the command buildings, barracks, baths and stores were arranged in a predetermined order in a rectangular area of about 450*500 metres (18.5 hectares) with three gates. The castrum's 3 metre wide stone walls were divided by towers, which were often rebuilt in differing shape from the ruins after the major destruction. A regular network of streets was laid out in the inner area of the legion camp, and this network of streets, together with the city walls and moats, still defines the street network and layout of the city of Vienna today. However, the archaeological excavations have not been able to reconstruct this regular layout in the Austrian capital, no finds have been recovered from the northern part of the castrum and no building foundations have been identified. The excavated Roman city wall in this section followed a natural break between the Maria am Gestade and the Ruprechtskirche. Since it is unlikely that the Romans in Vindobona deliberately deviated from the usual patterns, it can be assumed that the fortress wall may have suffered some irreparable damage that prevented it from being restored to its usual form. No barbarian opponent of the time was capable of such a feat, only the Danube. 

The line of effect of the Salzgries-arm within the legionary camp. (source)

There are two plausible scenarios for the destruction; a gradual erosion, which has been taking its toll over decades, gradually eroding the high bank and the fortress wall, and a single, extraordinary event. The latter is more likely. Sometime during the 3rd century AD, an extremely high flood may have flowed down the then westernmost branch of the Danube in Vienna, which science has named the Gonzagasse-Danube from the street that runs along its present-day course. This was the branch of the Danube on the banks of which Vindobona was originally built. The Roman legionary camp, however, was situated on the outer curve of the bend, where the proximity of the current line meant that bank erosion could occur even at mid-water. This was probably not simple riverbank erosion, but the displacement of a branch of the Danube, which also had a tectonic prediction in the fault lines of the Pannonian clay layers forming the terrace material, i.e. slides could have exacerbated the situation. 

The Danube has carried away more than 100 metres of the river terrace, shortening the lower reaches of the Ottakringer stream, removing up to several million cubic meters of sediment material from the Prater terrace, and at the same time from the western suburbs of Vindobona and the northern corner of the castrum of Vindobona. It is even possible that the suburban amphitheatre stood on the same site and also collapsed into the Danube. Similar changes in the riverbed were not at all uncommon in the pre-regulation period in the vicinity of Vienna, with sediment or other riverbed material often blocking off branches and causing islands, gravel bars and even settlements and bridges to be demolished in search of new routes. Severin Hohensinner's images illustrate this process over the last two millennia. 

42 steps to Maria am Gestade church

It is thought that material from the collapsed wall of the camp was used in Roman times to stabilise the collapsed bank and rebuild the northern wall of the camp along the newly formed river branch, which science calls the Salzgries branch from another street. This street name is also an evocative geographical name, a reminder of the salt trading ships that harboured here. Vindobona was by then past its heyday, having experienced a decline in socio-economic terms broadly similar to that of Aquincum. At one point in its history, a dwindling and impoverished population moved within the fortress walls until, sometime in the early 5th century, Roman administration ceased and the camp and its suburbs fell into ruin. If there was a continuity in the population, archaeology has found no evidence of it, the latest coin dates from 408 and after the middle of the century a layer of no archaeological remains was formed over the Roman ruins. 

Steps to the Ruprechtskirche, Vienna's oldest church

But the Salzgries branch of the Danube remained where it was, in the northern foothills of the ruined Roman fortress walls, and a thousand years later the church of Maria am Gestade was named after it. The name was a timely one, for the river, which was once quite navigable in size, gradually became silted up and narrowed during the 12th century, and the Danube bed moved away from the high bank to the north-east to form the so-called Porzellangassen branch, but still remained within the present-day Danube Canal to the west. 

Riverbed changes during the antiquity and in the Medieval Era in Vienna's 1st district.
1. Gonzagagasse-branch 2. Salzgries-branch 3. Porzellangassen-branch 4. Ottakringer stream
10. Wienfluss 11. Trench system of Vindobona (source: Wasser | Stadt | Wien)

The shifting of the Danube riverbed in the 3rd century left such an indelible mark on Vienna's urban structure that it affected not only the differences in geomorphology but also the city's road network. Neither the thousands of years of human landforming nor the great Viennese river regulation of 1875 were able to erase the work of the Danube that had been preserved precisely because of the building development. And if we listen carefully to the geographical names that speak, they tell us about the historical and geographical changes that have taken place over the millennia. 

Literature :

• https://tobias-lib.ub.uni-tuebingen.de/xmlui/bitstream/handle/10900/61026/CD71_Gietl_et_al_CAA_2003.pdf?sequence=2&isAllowed=y
• https://www.wgm.wien.at/hydrogeologische-forschung/news/flut-von-vindobona
• https://www.geschichtewiki.wien.gv.at/Salzgries
• https://www.wien.gv.at/kulturportal/public/grafik.aspx?bookmark=0nZLRk2zFUYHn7dFw-aI3RRwpAtZGVBFvuBteonQ1N1C4dSRsFu7fFg-b-b
• https://de.wikipedia.org/wiki/Vindobona
• https://www.wgm.wien.at/fileadmin/docs/hydrogeo-forschung/2022/Vortr%C3%A4ge/Pr%C3%A4sentation_WGM2022.pdf

Translated with DeepL.com (free version)

L'ouverture du Rollerdamm

MAGYARUL

IN ENGLISH

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

MAGYARUL

EN FRANÇAIS

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.

Heustadlwasser

MAGYARUL

Since 1875 there is no flowing Danube water in Vienna's Heustadlwasser.  This was one of the many side-arms of the river now hiding in Prater park. Nowdays it is feeded by precipitation and ground water only. The Viennese river regulation measures has cut it off from the Danube and was mostly filled in with construction waste. The remaining parts can be found near the Ernst Happel stadium, it's lower third is cut through by the Prater's long alley.

Tina Blau: Heustadlwasser, Prater 1877

Despite the always windy weather in Vienna I happen to visit this Danube side arm in a period of calm. The sun has just risen and there was absolutely no wind. The Prater became slowly populated by runners, hikers, cyclists. There was a stillness in the air despite a highway is cutting through the park. These pictures (and the Danube as well) are reflecting this morning atmosphere. 

Plan of the Heustadlwasser in Vienna

If you visit Vienna it is worthy to explore these hidden side arms of the long lost Viennese Danube, reflecting the pre-1875 landscape.

Revitalization of the Wienfluss

MAGYARUL

19th-century urban development involved the development of sewerage. Until then, the rivers were the main collectors, and the smaller streams served as channels. The Ördögárok stream in Buda, and the Rákos stream in Pest exuded unbearable stench before being eradicated. The second capital of the Austro-Hungarian Monarchy partly buried, partly forced underground the putrid channels which emanated putrid stench and usually also served as garbage dumps. Few people know that at that time the capital of the Monarchy also faced similar problems. There a firm and drastic intervention was necessary because of the floods and disease risk of the Wien river, which gave the name of the city. 

The Wien river being covered, ca. 1895.

The rapid improvement of the water quality after the installation of sewerage confronted Vienna city planning with new challenges. The river is no longer considered an enemy, and they slowly take the first step to the figurative and literal rehabilitation of the Wien river. The river, which not only gave the name of the city, but during its history also defended it from the enemy.

The case of the chicken and the egg – Which Wien was before?

The name of Wien was first used in the Salzburg Yearbooks of 881, in the form “ad Uueniam” (ad Weniam), but it is not clear whether it refers to the city or to the river. In Lower Austria it is quite frequent that a settlement along the Danube is named for the local tributary river (e.g. Enns, Ybbs, Aggsbach etc.), thus historians and etymologists think it likely that Vienna was named after the Wien river.

The Wien river as the natural line of defense of Vindobona

The river had a special importance for the development and progression of Vienna. It played a strategic role in the city’s southeast line of defense. In ancient times the legionary camp of Vindobona was surrounded on two sides by the Wien river and the Ottakring creek, forming two natural ditches around the settlement. In Roman times, the ramose side-branches of the Danube created a veritable archipelago on the widening floodplain, and the Wien poured into one of these branches.

The mouth of the Wien river (right), and the city walls of Vienna in 1686

Just like in Csallóköz – the Schüttinsel to the south of Bratislava/Pozsony/Preßburg –, the main branch of the Danube in Vienna was not suitable for navigation. The Donaukanal known today started to take shape in the Middle Ages from a side branch of the Danube, where the sailors could approach the imperial city, like they did on the Moson branch of the Danube in the Hungarian section. The Wien poured into the Danube at the easternmost bastion of the city, where above its mouth it formed a section of the moat called Graben.

The river bed before regulation

The duck of Linz

MAGYARUL

In the City of Wien, the people still remember the greatest flood along Danube, from Regensburg to the Kingdom of Hungary. They still remember, despite it happened 500 years ago, and the chance it would happen again is very low. In July and August of 1501. the heaviest rainfall hit the forehill region of the Alps in Austria and Germany causing a flood never seen before. North from the Danube basin, along the Elbe and the Oder vast deluge flooded the lands, just like back in Noah’s age.

High water mark collection in Passau (photo: cruises.about.com)

 

Lighthouses of the Danube

 

Heartly I admit that until last week I had no knowledge of the Danubian lighthouses. At least I had a suspicion that maybe I have seen one in Vienna. I was quite sure that there must be some in the Danube-delta, one for every branch, but those are belonging to the Black Sea – I thought. Then I came upon Béla Vályi’s monumental map on the Danube valley in the known Hungarian geographer, Jenő Cholnoky’s heritage. As I was browsing these sections I saw something strange in the mouth of the Tisza river: a lighthouse! Wow, does it still exists?