Donauinseln: 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.