The Oldest Danubian Island in Vienna - The Alberner Schotterbank

MAGYARUL

Let's start with a riddle: Which is the oldest natural island still in existence on the heavily regulated, straightened, and de-insulated section of the Danube in Vienna? If there is one at all. 

Of course there is; otherwise, the question would be pointless to begin with, and there would be no reason to even write this post. In any case, this is by no means obvious on the ground; in fact, given its morphology, it should rank among the youngest islands, and everything points to the fact that this riverbed was created by humans between 1972 and 1988, when the Danube regulation carried out between 1870 –1875 was revised in Vienna, creating the bleakest urban zone in the river’s history, known as the Überschwimmungsgebiet, where the natural riverbeds of the time lay on the banks for a long time, like dead fish after the cyanide pollution of the Tisza river. A hundred years later, these remains were dredged up and buried beneath a 21-kilometer-long artificial island called the Donauinsel, which has one positive aspect: it was ultimately not built up with office buildings and apartments, but instead developed into a city park, featuring varied topography and a diverse shoreline despite its straight, paved banks. 

Along the Donauinsel, bays, peninsulas, and quieter stretches of water bordered by rock embankments have been created—and even separate Danube islands—to replace the natural tributaries that have been eliminated and so to increase biodiversity. One such artificially created island is the Albern Gravel Bank (Alberner Schotterbank), which could easily be called an island due to the floodplain forest that has developed on it, interrupted at only one point by the highly spectacular pipeline system connecting the Schwechat oil refinery with the Lobau oil terminal. 

On Monday, May 11, 2026, in the early afternoon, during a low-water period of 150 centimeters—with the water level slightly receding—measured at Wildungsmauern, a significant overflow was observed in the approximately 20-meter-wide side channel next to the Alberner Schotterbank. The water flowed extremely rapidly in the deep channel between the extremely steep, eroded bank walls composed of massive pebbles. On both sides, tree roots hang in the air. There are two human-made reasons for this: one is the Freudenau Dam, downstream of which lies the Alberner Schotterbank; the other reason can be traced back to the same project, albeit somewhat indirectly. This is because beneath dams, the riverbed suddenly deepens, the original water level drops, and the islands are left dry. 

That’s what happened here as well; this gravel bar is very close to the dam, and it functioned as a gravel bar right up until the dam was built. As a result of the drop in water level downstream, it became an island, which is why the forest was able to grow there, and why the side channel began to dry up. In Austria, they typically don’t leave things like this alone and set about dredging. Between 2023 and 2024, with a brief interruption when the Boris flood deposited an astonishing amount of silty sediment and debris in the area, they dredged out the deep channel still visible today, despite protests from regular beachgoers [1]. The dredged gravel was used to counteract the deepening of the main channel and was spread out below the Freudenau dam. Some online maps still show the old situation of the river, so many visitors may be surprised to find that the island can no longer be reached on foot even at low water, a fact that beachgoers have resented ever since; conversely, the wildlife is quite grateful for the isolation. 

The Alberner Schotterbank in 1856.

The Alberner Schotterbank first appears on Pasetti’s 1856 nautical chart of the Danube. It was closer to Mannswörth than to Albern, and was located on the opposite bank. At that time, Albern was a small fishing village belonging to Kaiser Ebersdorf, which suffered greatly from the Danube’s floods. It was destroyed by the “Himmelfahrtsgieß” flood of 1501, and then by the “Allerheiligengieß” flood of 1787, when erosion by the Danube washed away 85 hectares of land, including the village itself [2]. It was then that the fishermen relocated to the site of the present-day settlement. In 1809, Napoleon, passing through here, dismantled the village to build a pontoon bridge using the beams from the houses in Albern.  

The Alberner Schotterbank in 1938.

The upsilted island before the dredging, 2023. 

The current situation

On Pasetti’s map, it appears that one of the islands in the vast Danube side channel—which was dammed off between 1836 and 1841 opposite the settlements of Albern and Mannswörth—was split in two by the dam, with the smaller, shoal-covered section remaining in the floodplain. We are most likely witnessing the very moment of the Alberner Schotterbank’s birth; in other words, this island in the Danube—now part of Vienna—will soon be blowing out two hundred candles on its birthday cake. The Albern gravel bar is a true relic. It is not so much its formation as its survival that is considered a miracle. Although it is inseparable from the history and territory of the Donauinsel today, it is very distinct from it.

Recommended and cited literature:

 

[1] https://www.krone.at/3157759

[2] Wasser | Stadt | Wien 

Black Lacquer Danube

MAGYARUL

Following the river regulation carried out in Vienna between 1870 and 1875, and the subsequent urbanization, very few of the original branches remain of the once anastomotic Viennese Danube. Nevertheless, the old hydrographic names have survived to this day in the Austrian capital; at every turn, we come across street names and neighborhood names such as Am Hubertusdamm in Floridsdorf, Überfuhrstraße, and Floridsdorfer Aupark, all of which are linked to the history of the former Danube island, Schwarze Lackenau. Despite the fact that this island ceased to exist more than a century and a half ago, the flood-prone lands were built over, and its buried, then partially revitalized tributary was left as green space—perhaps out of respect—which anyone can walk through, provided they are aware of what once lay beneath their feet. Which, of course, is by no means obvious.

The Schwarze Lackenau before the Viennese river regulations

Above Vienna, the Bisamberg on the left bank is in a similar position to the next “gate” downstream, between Devín and Hainburg, dividing the Austrian Danube into sub-basins. Above it, the Tullnerfeld once boasted a Danubian archipelago as rich as the Marchfeld that opens up below the Bisamberg. The Schwarze Lacke was one of the first left-bank Danube tributaries of the Marchfeld, branching off below Langenzersdorf opposite Leopoldsberg—easily recognizable by its church—and rejoining the main channel near Floridsdorf via a seven-kilometer-long, inverted “S”-shaped channel. The island it surrounded, like many others in the Vienna area, was known as an “Au”; today, the hydronym Schwarze Lackenau has become the name of the settlement. 

In Vienna, although very little remains of the old Danube islands, their history is well documented; according to the maps in the exemplary volume Wasser | Stadt | Wien, this tributary—alongside which lay anywhere from one to three separate islands—already existed in various forms as early as the 16th century. In contrast, only a single settlement on its banks, Jedle(r)see, withstood the destruction wrought by the Danube, which regularly flooded the Marchfeld and evidently Vienna, as evidenced by the flood of March 1830, commemorated on a plaque on the wall of the local manor house of the Hungarian Counts of Erdődy.

The floods that became increasingly frequent during the 18th century and reached ever-higher water levels were particularly dreaded events in Vienna. In addition to the damage caused to human life and property, each time the floodwaters receded, new sandbars and islands formed, the shape of the old ones changed, some branches silted up, and others began to develop into main channels. North of Vienna, the regulation of the Schwarze-Lacke branch also became necessary due to such a change in water flow; by the mid-18th century, there were fears that the main branch of the Danube was increasingly diverting toward the Marchfeld via this branch, these channel shifts not only threatened the surrounding agricultural areas with destruction but also endangered Vienna’s trade, should the former right-bank shipping routes silt up. Thus, it was necessary both to ensure that the Danube branch—considered the predecessor of the Donaukanal—near Nußdorf on the right bank received sufficient water supply and to close off the left-bank branches. 

After seven years of debate, in 1776 the Aulic War Council (Hofkriegsrat) approved the plan submitted by Hubert János Zsigmond, a hydraulic engineer born in Sopron, Hungary, and commissioned him to build a 7-kilometer-long protective embankment between Langenzersdorf and Nußdorf. This included more than 50 spurs extending into the main channel, which protected the new embankment from erosion. The course of the Danube had already changed significantly while the plans were being drawn up, so Hubert had to modify the plans as work progressed. The embankment, with its rather irregular course, closed off several smaller and larger river branches, each of which carried the potential for a breach during floods. One such smaller branch was the Scheibgraben, which nearly cut the Schwarze Lackenau area in half and was closed off at the last moment before a breach could occur. An embankment was also built across the island; the purpose of the Kommunikationsdamm was to ensure a connection to Nußdorf, and a ferry crossing operated at its end. However, the Hubertusdamm was completed at the very worst possible time. 

Toward the end of the 18th century, flooding became increasingly common along the Vienna section of the Danube; in some years, the Schwarze Lackenau was flooded several times. According to Historische Hochwässer der Wiener Donau und ihrer Zubringer, these occurred in the following order: (July 1771, January 1775, February 1776, June 1777, February 1784, then August, March, June, July, and August 1785, June, July, and August 1786). Barely four years after the embankment was completed, the greatest flood of November 1787 severely damaged the embankment and reopened the Schwarze-Lacke branch, which was later closed off again with a “shallow” dam (Seichdamm), but regardless of how it happened, the Hubertusdamm formed the foundation and the first section of the Marchfeld-Schutzdamm flood protection embankment, which was later built in a straight line all the way to the mouth of the Morava River towards the Hungarian border.

The original plans for the Hubertusdamm in 1783.

In Vienna, this regulation brought about extremely drastic changes between 1870 and 1875, permanently eliminating the Danube’s role in shaping the landscape around the city and enabling urbanization in the reclaimed areas. It also closed off the Schwarze-Lacke branch and cut off the western part of the Schwarze Lackenau island, which meant that the remains of the embankment built by Hubert were also leveled in the barren area of the Inundationsgebiet, a zone designed to divert floodwaters. Interestingly, the southern tip of the island near Floridsdorf remained intact; this is now the Floridsdorfer Aupark. 

The old and new route of the Viennese Danube between Jedlesee and Floridsdorf 1870-1875.

Humans took over the Danube’s role in shaping the landscape in the reclaimed floodplain, the Schwarze Lackenau area; while it was still an island, there were barely one or two houses there until the 1870s, typically shipyards, ferry stations, inns, or manor houses. Vienna’s urban expansion first reached Jedlesee; due to the housing shortage following World War I, the island’s area was subdivided in two phases, with primarily small gardens and single-family homes being built—a character the neighborhood has managed to preserve to this day. Although the Schwarze-Lacke branch was gradually filled in by 1939 at the latest, the area of the old riverbed was not built-in. 

The Schwarze-Lacke-Duna, which had already been filled in, and the parceled-up island in 1939

The section downstream of Jedlesee has preserved the shape of the riverbed the longest; this part was filled in after 1945 with debris from buildings destroyed during World War II, and later, according to some reports, the work continued using urban garbage and soil contaminated by industrial pollution—a process that, based on aerial photographs, was still underway as late as 1956. Based on a site visit, the filling was by no means uniform morphologically, likely due to land ownership issues. The parts of the private properties along the shore that extended into the riverbed typically preserved the deepest sections, alternating between the island and the shore sides, primarily in the section above the Jedlesee church. There is also a longer depression next to Teslagasse in the wooded area of Aupark Jedlesee, but where the authorities built playgrounds and sports fields, the leveling was much more thorough. 

The southern section with the latest landfill in 1956.

The last major anthropogenic intervention took place between 1984 and 1992, when the drop in the groundwater level in the Marchfeld—caused by the subsidence of the Danube riverbed—began to threaten agriculture. The harmful effects of Danube regulation necessitated another intervention; the Marchfeld Canal was constructed as part of the revitalization of the northern section of the Schwarze-Lacke branch. This canal actually branches off from the Danube at Langenzersdorf, but runs parallel to the Danube for several kilometers; utilizing the former Schwarze-Lacke branch, it was routed eastward and extends almost all the way to Dévény. 

Water is only present on this section, but it seems that even this is an improvement compared to conditions in Vienna.

The revitalized northern section of the Schwarze-Lacke-Danube (now known as the Marchfeld Canal)

Here and there, the piles of soil used for backfilling are visible

Until 1870, the only way to photograph the church at Jedlesee was from a boat

The Lorettofield sports area, with the Jedlesee church—originally built on the banks of the Danube

Saint Florian and the 1830 Floodmark
on the Wall of the Erdődy Manor House in Jedlesee.

Translated with DeepL.com (free version)