Grazbach

The Grazbach is a city stream in the Styrian capital that today runs entirely underground. It begins in the St. Leonhard district, where the Kroisbach and the Leonhardbach come together. Its course runs beneath streets such as Sparbersbachgasse, Dietrichsteinplatz, and Grazbachgasse. Originally, the stream flowed in the open through the eastern suburbs and emptied into the Mur near where the Augartenbad pool stands today. Because it often dried up in summer and served as a sewage channel, it was straightened and built over starting in 1879. The work was carried out in two stages: the lower course was moved underground between 1880 and 1883, and the upper course between 1885 and 1887. In the process, the confluence was also relocated to the northern edge of the Augarten park.

Inside the canal system, you will find an unusual design, mainly in the area of Grazbachgasse. Here, three parallel channels run side by side. The wider middle channel carries the relatively clean water of the Grazbach, while the two side channels take wastewater from the sewer system. Under normal conditions, these flows stay separate, so the walkways between them remain dry and can be walked on. During heavy rain or flooding, however, the flows can mix, sending untreated combined sewage into the Mur. To preserve the river's ability to cleanse itself, a central storage canal was built as part of the construction of the Puntigam hydroelectric plant on the Mur; it is designed to hold large volumes of water during extreme weather.