Medieval Vienna was situated at the main arm of the swiftly flowing alpine Danube. From the fourteenth century onwards, the river gradually moved away from the city. This marked the beginning of 500 years of human intervention to prevent further displacement of the river and to preserve the waterway as a vital supply line. Archival research and the GIS-based reconstruction of the past riverscape allow a new view about the co-evolution of the city and the river. Following major channel changes in 1565/1566, repeated attempts to force the main arm into the old river bed were undertaken. By the early seventeenth century, the Viennese had accepted the new situation. Resources were now spent on maintaining the waterway to the city via the remaining Wiener arm. After the second Ottoman siege in 1683, improving the navigability of the Wiener arm, in conjunction with major expansions of the fortifications, became the main issue. Between 1775 and 1792, the first systematic, effective flood protection measures were established. These substantially influenced fluvial dynamics and enabled urban development in parts of the former floodplain. The all-embracing transformation of the dynamic riverscape into stabilised areas enabling urban growth and secure waterways was not achieved until 1875. With this successful “re-invention” of the Viennese Danube, an irreversible path was struck in the common life of the city and the river, a path which is still decisive for the interaction of Vienna with that great European river.

As part of an interdisciplinary project on the environmental history of the Viennese Danube, the past river landscape was reconstructed. This article describes the different types of historical sources used for the GIS-based reconstruction, the underlying methodological approach and its limitations regarding reliability and information value. The reconstruction was based on three cornerstones: (1) the available historical sources; (2) knowledge about morphological processes typical for the Austrian Danube prior to regulation; and (3) the interpretation of past hydraulic measures with respect to their effectiveness and their impact on the river’s behaviour. We compiled ten historical states of the riverscape step-by-step going backwards in time to the early 16th century. After one historical situation had been completed, we evaluated its relevance for the temporally younger situations and whether corrections would have to be made. Such a regressive-iterative approach allows for permanent critical revision of the reconstructed time segments already processed. The resulting maps of the Danube floodplain from 1529 to 2010 provide a solid basis for interpreting the environmental conditions for Vienna’s urban development. They also help to localise certain riverine and urban landmarks (such as river arms or bridges) relevant for the history of Vienna. We conclude that the diversity of approaches and findings of the historical and natural sciences (river morphology, hydrology) provide key synergies.

In the relation between urban development and the Viennese Danube different periods can be identified from the late 17th to the early 20th century. These periods were strongly intertwined with both the history of the river and the history of the city. Urban expansion into the floodplains is demonstrated in this paper by investigating the island Unterer Werd, next to the city centre. In the late 17th century the fluvial dynamic still hampered urban development on the island. First measures to stabilise the river banks and to protect buildings from floods were taken soon thereafter, but the majority of practices aimed at mitigating the risks and impacts of the frequent floods: inundation was a part of the arrangement and the main target was to minimise the potential impacts. This practice also prevailed after the 1830s, when urban expansion began to move into the north and northwest of the island and the Danube floodplains were considered an important land resource for the growing city. In connection with new technologies and available means to channelise the river, the relationship between Vienna and the Danube changed fundamentally. Urban development in the riverine landscape gained new momentum. This process was initiated before the Great Danube Regulation from 1870 to 1875 was completed, the rate of growth accelerated after 1875. The last decades of the 19th century mark a turning point in the urban development of Vienna, with expanding urban areas becoming dependent upon a well functioning and maintained flood protection system.

Alluvial rivers can show unpredictable channel changes and humans living along the river corridor repeatedly have to cope with the alterations of their physical environment. This was specifically the case in the mid-sixteenth century, when the Viennese were confronted with one major problem: the Danube River successively abandoned its main arm that ran close to the city and shifted further north. This was at the time when Vienna became the permanent residence of the Holy Roman Empire (except from 1583 to 1611 when it was moved to Prague), due to the Habsburgs holding the crown. Vienna was also the capital of the so-called Danube Monarchy, which came into being in the early sixteenth century. The city assumed increasing significance, being home to and hosting important authorities and persons. In particular after the first siege by the Ottoman army in 1529, the resource need for a complex fortification system was extremely high. This paper aims to highlight: (1) the morphological Danube dynamics together with floods and extreme weather situations in the sixteenth century; (2) the main actors in the transformation of the Danube; (3) changes of the river's course from 1550 to 1600/1650 and the consequences for bridging the river and the infrastructure as a whole; (4) the massive engineering measures that were undertaken in order to secure Vienna's requirements in the sixteenth century; (5) the question of floodplain settlements, and (6) the contested use of resources on the Viennese Danube floodplain.

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