Lobau flood protection: LobAu: intensive care unit with power outage 2.0

(Continuation from: LobAu (weh) – intensive care unit with power outage – in my district on September 2nd, 2024)

In September 2024, large parts of Austria were hit by massive floods that cost human lives and destroyed many settlements, commercial facilities, roads and agricultural crops. Vienna was affected, but escaped with a black eye. The Vienna Löbau was also flooded due to the unusually high water level of the Danube. For a few days it was almost like a water forest again, like it was back when the “Esslinger Ford” was still a public natural swimming pool.

The flood restricted the Lobau’s usability for recreational purposes for a few days, but gave the Au a “breath of relief” after weeks of drying out – an emergency unit in the intensive care unit, so to speak. Everything saved and recovered? No! The water shortage will soon occur again in the riparian forest. The city of Vienna’s water supply was already stingy in the summer and will be stopped again in the winter.

There is also another potential danger for the Lobau: Since during floods, as was the case recently, the Danube water backs up “from below”, i.e. from the “Schönauer Schlitz” below the Lobau, into the Lobau and the water does not flow through “from above”, masses of mud become left behind. In a natural, dynamic floodplain system, these would be flushed out again with the water flowing through from above. However, the Lobau is denied this, and the “salutary” flood has the disadvantage that the subsequent effect is that it even accelerates the silting up of the area.

What would be necessary is frequent and extensive flow through the riparian forest “from above”, including from the Danube and the new main stream of the Danube. This would also clean the gap space and feed the groundwater.

What the September floods showed is the importance of intact, natural areas as flood protection. The progressive sealing of the soil not only needs to be slowed down, but there is an urgent need to reverse the trend in the sense of repurposing and renaturating areas at risk of flooding. By creating space for the water, you take away its force. What was demonstrated in the Lobau is the indispensable potential of the floodplain area as a natural retention basin. This also raises the question of how the large-scale soil sealing that would be expected as a result of the (still not abandoned) Lobau Motorway affected this potential.

This leads to the question: In which drawers have the Vienna magistrate’s ambitious plans to reconnect the Lobau waters to the Danube disappeared? They are concerned with preserving the character and diversity of a dynamic riparian forest. The (self-proclaimed) climate model city is asked to plan courageously and responsibly for the future and to preserve and protect the dynamic riparian forest.

In addition to providing recreation for people and preserving biodiversity, Lobau also provides efficient climate and flood protection!