GE-RM
Enns in Salzburg
The river Enns: People, river and nature
The source of the Enns is located in the Radstädter Tauern at an altitude of 1,735 m above sea level. The river is strongly influenced by its alpine catchment area in Salzburg. On its way the river covers 1,505 metres in altitude until it flows into the Danube between the towns Enns and Mauthausen at 245 m above sea level.
Looking at the structures that the Enns would naturally form in the study area, gravel banks, alternating shallow and steep banks with eroded sections dominate.
GE-RM
Enns in Salzburg
The river Enns: People, river and nature
The source of the Enns is located in the Radstädter Tauern at an altitude of 1,735 m above sea level. The river is strongly influenced by its alpine catchment area in Salzburg. On its way the river covers 1,505 metres in altitude until it flows into the Danube between the towns Enns and Mauthausen at 245 m above sea level.
Looking at the structures that the Enns would naturally form in the study area, gravel banks, alternating shallow and steep banks with eroded sections dominate.
In the GE-RM, the Enns between the border to Styria and the confluence of the Grießbach with the Enns in Flachau as well as the lowest section of the river Taurach and its tributaries in the municipalities of Radstadt, Altenmarkt and Flachau were considered.
Overview flood risk and ecological status
The inventories resulting from the preliminary study are used to close knowledge gaps that exist with regard to flood risk and river ecology. The aim is to identify sectoral deficits and comparing them with the existing objectives in order to draw up a concept of measures based on them. The diagram provides a summary of the deficits of the rivers Enns and Taurach. While the flood risk is relatively low due to the extensive measures already implemented, ecological deficits dominate over the entire investigated stretch:
Deficits and opportunities
Deficits
Ecological status
The river regulation measures completed in the 1980s massively changed the Enns in Salzburg. The river was straightened and routed in a trapezoidal profile. The social goals of the time, to increase agricultural productivity and flood protection, were achieved. What remained, however, was a poor-structured river with steep, rock-secured banks. The character of a natural watercourse was lost. Due to the regulation works, the Salzburg Enns today has a moderate or worse ecological status.
Fish fauna
Current studies show that hardly any fish still live in the Enns. Their frequency and biomass are low, the status of the fish fauna is consequently poor to bad.
This is not only due to the lack of habitats for fish in the Enns itself. In many cases, the tributaries are in poor ecological condition. Some mouths are not passable for fish. Where riparian woods are missing, waters can overheat and nutrients pollute the water.
The brown trout is the so-called leading species in the entire study area and was detected at every monitoring site. However, the so-called biomass – which is simply put the weight of all fish – is problematic since it is far too low. There are also deficits with regard to the different age stages of fish.
Even though the course of the Enns was already influenced by the increasing use of the Enns valley at the time the Franziszeische Kataster was drawn up – the Radstadt sheet was drawn in 1829 – the map still shows a much more curved water course and also some small islands within the Enns:
Flood risk
In the last 20 years, numerous measures have already been implemented to protect settlements almost entirely against a 100-year flood. Nevertheless, buildings, roads and infrastructure are at risk of flooding – especially if the interaction with torrents flowing into the Enns is taken into account. Furthermore, events beyond the 100-year event cannot be ruled out. Supplementary to additional structural measures, the so-called residual risk must be reduced through non-structural measures such as disaster control planning and risk communication.
Opportunities
Nature protection
Floodplains and wetlands have always accompanied the Enns River in. Some of them were preserved until today and are now protected, for example the Iris meadows or the Mandlinger Moor. They are the starting point for ecological improvements. When considered together, mutual synergies can arise for the different ecosystems.
Of course, the species that use these ecosystems as their habitat also benefit from this. In the Mandlinger Moor, for example, the Large White-faced Darter (also called Yellow-spotted Whiteface) can be found. This dragonfly has only been found at this single location in inner alpine Salzburg.
Recreation and leisure
Enns and Taurach are popular local recreation areas for locals and guests. Walking, hiking and cycling paths run along their banks. Often there are opportunities to experience the element of water up close. Measures that actually serve flood protection or ecological improvement can also take up this aspect. After all, who doesn’t like to spend time by the water and experience a living river up close?
An example of this is an already implemented measure on the Enns in Altenmarkt, whose primary objective was flood protection. However, due to the proximity to the settlement, the area of the measure also became an attractive local recreation area.
Overview Measures Enns – Salzburg
39 measures for reduction of flood risk
Measures to reduce and avoid flood risks can be very different. The most effective measures are combinations of structural and non-structural measures. In the GE-RM Enns 39 measures are proposed to protect the population from floods. These range from the preservation and protection of existing retention areas to the construction of retention basins and dams and to the protection of individual objects. In the planning process, these measures were coordinated with ecological objectives in order to use synergies.
13 measures to improve river continuity
Fish migrate naturally. This enables them to use different habitats. For example, different habitat characteristics are important for reproduction than for growth or nutrition. Therefore, fish migrate within river systems to find the optimal conditions for their needs. Today, numerous artificial barriers impair fish migration. In order to allow fish and organisms to migrate again, 13 measures to improve continuity are proposed on the river Enns in Salzburg.
36 measures to improve river morphology
To gain land for settlements and agriculture, many of our rivers have been straightened and regulated. As a result, the typical morphology of the river is restricted and therefore important habitats in the water and on land are usually missing. For example, gravel banks and islands are crucial for so-called gravel spawners (i.e. fish that depend on gravel for spawning) or for birds that breed in these places. 36 of the proposed measures focus on improving the morphological conditions of the water bodies, whereby these measures also partly support the objectives of flood risk management.
Example of a concept of measures
The map shows an example of the concept of mesures for a section of the GE-RM Enns in the area of Radstadt Ort and Taurach. The Enns is strongly regulated in this area, therefore the concept provides for numerous measures to revitalise the Enns. Flood protection for Radstadt in the area of the sawmill is also taken into account. Another focus is on risk communication and the preparation of disaster control plans.
Photo credit:
Example of measures local recreation and leisure & example map concept of measures: Land Salzburg