Semi natural green Danube islands in the grasp of megacities

Abstract

The majority of European cities have been developed on the banks of natural rivers, often in places where the shallow riverbed river helps to form natural crossing points and islands. The fate of islands in the urban environment has been varied in different countries and cities. In terms of urban development, a determining factor is how capricious the river flow is and how often the island is flooded. Permanent buildings or neighbourhoods may have developed mainly on islands that are not exposed to flooding (e.g. Ile de Cite, Paris). Accordingly, flooded islands have remained in a more natural state and are nowadays a valuable element of the green space system of large cities.
The 2850 km long Danube is the largest river in central Europe, originating in the Black Forest (Germany) and reaching the Black Sea on the Romanian coast. Along its long route it breaks through mountains and meanders across plains, and on its banks many settlements have developed over the millennia. The four major Danube-coast metropolises (Vienna, Bratislava, Budapest and Belgrade) are all located on the lower, alluvial river courses, where the river forms islands by depositing debris from the mountains. Thus, all the above-mentioned cities have more or less natural islands. Many of these islands have not been affected by urban development and have not been built on because of the constant threat of flooding. However, some of them have been removed over time, mainly to provide safe waterways and flood protection, but the remaining islands are the most valuable elements of the green space systems of capital cities. Today, urban pressure on these islands is increasing. Modern methods of flood protection offer the possibility of making the islands flood-free and thus they have become target areas for various urban developments. The question is whether the aim is to change permanently these last remaining semi-natural areas with valuable fauna and flora in large cities and give them an urban character. Current development plans still tend to treat these islands as green spaces, but envision a much more intensive use of open spaces, with the associated infrastructural investments. The question is whether due to the proposed developments these unique element or elements of the green space system will finally disappear from the Danube metropolises, which will permanently change the character of these cities.
In this article, we compare the Donau (Danube) Island in Vienna and the Óbuda (Shipyard) Island in Budapest. Although the circumstances in which the two islands were created are very different, their development principles in the 1970s and the urban pressure for development since the 2000s show many similarities. In our article, we highlight these interesting parallels (Auböck and Bakay, 2020). As the Vienna Danube Island is ahead of the Budapest Óbuda Island in terms of development, it is interesting to draw lessons from the developments there. What are the directions to keep in mind in the increasingly urgent development of Óbuda Island, and what are the traps and dead ends to avoid. These lessons can also be applied at the development other semi-natural Danube-islands in an urban environment.