The Liesing rivulet has always decisively marked the city landscape and the development of the southern districts of Vienna. Its waters supplied the villages in the Liesing valley already in the 19th century and were an important prerequisite for their development to important industrial locations. The population grew accordingly who fast and often suffered from cholera and typhus epidemics as a consequence of frequent drinking water contamination.

Today the banks of the Liesing belong to densely developed urban areas and are a residential area much in demand. The structural regulation and flood prevention measures in the valley between 1947 and 1969 were a prerequisite for this development. Aspects of ecology, water quality and recreation, however, were not considered in the course of the "hard" regulation.

New methods in water engineering

The 1990 amendment of the Water Law authorises water engineers to strike new paths and thus to harmonise the demands of flood control with the improvement of the ecological efficiency. The Vienna Municipal Departments 45 (Water Engineering) and 30 (Sewage and Wastewater Engineering) have demonstrated for years, how water protection and cross-linking, revitalisation and near-natural water engineering can be implemented in a metropolis.

One focus of their activities is the model project developed by an interdisciplinary expert team "Revitalisation of the Liesing rivulet", which integrates the objectives of ecology, water engineering and landscape planning. Implementation is effected in phased projects: the intercepting bypass canal in the Liesing valley to be built by the MA 30 will decisively improve the water quality. The near-natural design of the water course and its banks is carried out by the MA 45 and will create a green belt along the water of city-wide importance.

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Ecological model

Austria committed itself in 1999 in the framework of the EU Water Framework Directive to implement a programme, which shall guarantee a "good ecological status" for running waters. This means: an ecosystem influenced by human activity, but nevertheless rich, balanced and viable. The ecological model identifies three decisive criteria to achieve this status: the improvement of water quality, the design of riverbank structures and the activation of bed load transport. Inter-gravel spaces are of particular importance, which in the near-natural sections of the Liesing (the Liesing in the Vienna Woods) are populated by aquatic microbes down to a depth of maximally 70 cm, and which are the "secret" of the proverbial self purification power of a water body.

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A near-natural rivulet is created

In the 90ies the headwaters of the Liesing were the centre of the revitalisation activities. At that time the experts mainly focused on the near-natural designing of the former bed load basin near the Willergasse, which lead to a considerable improvement of the water continuum. Moreover, several bank regions of the Upper Liesing were widened and their natural state was restored.

The main focus of the years to come shall be the 5.5 km long section of the lower reaches of the Liesing between the purification plant Blumental and Unterlaa. In this connection it can be assumed that the ecological value of the rivulet course will definitely be improved by the construction of the Liesing valley intercepting bypass canal.

The objectives of the near-natural revitalisation of Blumental-Unterlaa comprise:

• Improvement of the possibilities to experience and to access the water body by means of a new water course design and new paths
  
• The Liesing as integral part of the village character. Thus, walking paths will lead to the surrounding landscape and offer many possibilities of recreation and sports
  
• The creation of a biking trail in the Liesing valley, which will upgrade the wide biking network in the South of Vienna and connect the biking trails in the city and Laxenburg, or rather the Vienna Woods and the villages in the Liesing valley
  
• The improvement of water quality to class 2 – as a basis for the ecological efficiency of the water body and the upgrading of the recreational value for the population
  
• The creation of new structures along the rivulet and in the water bed to promote a high biodiversity and thus to activate the natural self purification power of the water body
  
• The connection of old rivulet bends. This measure shall create new habitat structures for typical lowland rivulet ecosystems. Planned riverbank widening and restructured meander sections will contribute to the formation of natural retention zones (flood protection zones).

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Information & Contact:

MA 45 (Viennese Water Engineering)
Dipl. Ing. Gernot Ladinig, Dipl. Ing. Viktor Friedl
Tel. +43 1 40 00–96 571
Fax +43 1 40 00–72 90

MA 30 (Viennese Canal)
Dipl. Robert Nowak, Ing. Josef Gottschall
Tel. +43 1 79 514–93 041

Planning offices:
planact
Dipl. Ing. Brigitte Hozang, Dipl. Ing. Anette Schawerda
Tel. & Fax +43 1 202 45 90

Ingenieurbüro Neukirchen
Tel. +43 1 533 45 64

Büro f. Landschaftsplanung
DI Marija Kirchner
Tel. +43 1 368 31 38