GE-RM
Pielach
The Pielach: Safe and livable!
The project area studied in the GE-RM includes the Pielach between its confluence with the Danube at Melk and the confluence of the Nattersbach with the Pielach east of Frankenfels – this adds up to a river length of almost 60 kilometres.
The Pielach rises in the northern Alpine foothills near Annaberg at an altitude of around 800 metres above sea level. The lower course in particular is a valuable habitat due to its closeness to nature and is designated as a Natura 2000 site.
GE-RM
Pielach
The Pielach: Safe and livable!
The project area studied in the GE-RM includes the Pielach between its confluence with the Danube at Melk and the confluence of the Nattersbach with the Pielach east of Frankenfels – this adds up to a river length of almost 60 kilometres.
The Pielach rises in the northern Alpine foothills near Annaberg at an altitude of around 800 metres above sea level. The lower course in particular is a valuable habitat due to its closeness to nature and is designated as a Natura 2000 site.
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 river Pielach. The overview shows how different the initial situation is in the various sections of the Pielach.
Section Danube to Neuhofen
Deficits
Flood risk
In this stretch, the Pielach is partly regulated. In between, there are largely unregulated sections (Neubach), where only local bank protection or local protection for infrastructure exists. In total, almost 300 buildings in this section are potentially affected by a 100-year flood.
River development
Deficits ragarding river structures are present in the Spielberg area, in the Albrechtsberg area and upstream and downstream of the Neuhofen weir. In addition to morphological pressures, the residual water and impounded stretches caused by power plants have a significant impact on the water bodies. Also some transversal structures in this area are only passable to a limited extent.
Opportunities
Public awareness
Due to the near-natural river landscape that is still partly preserved in this section, many places are used as bathing spots. In this way, the population can be made aware of how attractive near-natural rivers can be and what added value river restoration can bring to recreational areas.
Habitat for the Huchen
The formerly very healthy population of the Huchen is of specific relevance for nature conservation. The lower section of the Pielach is of particular importance due to its connection with the Danube and the other Danube tributaries of the FFH area Niederösterreichische Alpenvorlandflüsse. Even though riverbed sills restrict the habitat of the Huchen, it finds habitats in the Pielach. Due to its population in the Danube and its tributaries, the Huchen is also called Danube salmon.
Section Neuhofen to Völlerndorf
Deficits
Flood risks
In this section, significant impacts occur even during more frequent flood events (HQ30). The municipality of Markersdorf-Haindorf is particularly affected.
River development
Regarding river development, there is a need for action in this section at Haunoldstein, in the area upstream of the Eibelsau weir, in the area upstream of the Mühlau weir, in the area upstream of the Kremnitzbach estuary to the Salau weir and in the area upstream of the Salau weir.
The illustration shows the so-called administrative map of Lower Austria, which was drawn between 1867 and 1882. Even though interventions in the course of the river had already taken place at that time, the regulations that took place later have massively changed the Pielach.
Opportunities
European nature reserve
The entire section of the Pielach is part of the European nature reserve Pielachtal. The Pielach-Mühlau nature reserve, with an area of approx. 36 ha, is the largest remaining floodplain on the Pielach. It is located between Prinzersdorf and Wimpassing. More than 60 breeding bird species occur here, of which more than 10 can be found on the Red List – like the Sand martin in the picture.
Section Ebersdorf to Weinburg Weir
Deficits
River development
Compared to the lower sections, the section Ebersdorf to Weinburger Wehr is mostly classified as moderate regarding morphology due to the strong regulation (see photo). This applies especially for the sections Obergrafendorf and Klangen. With regard to passability, seven riverbed sills with limited passability (the photo shows the riverbed ramp upstream of Rennersdorf) can be identified in this section. In addition to the morphological pressures, the residual water situation caused by power plants (residual water stretches 90.9% of the section) can be identified as a decisive stress for the river ecology.
Flood risk
The municipality of Weinburg is designated as a risk area due to the high level of impact, also due to the hazards that arise in this area as a result of the Pielach tributaries.
Opportunities
Low-impact tourism
The Pielach Valley Cycle Path, which runs along the Pielach near Obergrafendorf, or the hiking trail Natura Trail Pielach have a high, also supra-regional value and open up opportunities for soft tourism.
Section Weinburg Weir to Dobersnigg
Deficits
Flood risk
In the upper section, flood risk exist in different areas. In Rabenstein in particular, flooding is to be expected from HQ30 onwards. Also in Kirchberg an der Pielach, although a flood protection project was recently implemented to protect the centre of the village, parts of the village are affected.
River development
The river morphology is mostly classified as moderate (see upper picture for the area upstream of Mainburg). Isolated areas with good morphology can be identified. Significant deficits in morphology can be found in the area of the Weinburg weir (see lower picture), in Hofstetten, Mainburg and Rabenstein, downstream and upstream of the village of Kirchberg.
Opportunities
Water nature trail
An educational trail in Rabenstein between the weir and the “Perger Bridge” with information boards on measures on the Pielach is being planned. This can be used for appropriate information facilities (e.g. information boards) and offers opportunities for public relations work and awareness raising for living and safe rivers.
Overview of measures on the Pielach
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 Leitha numerous proposals for measures to protect the population against floods were defined. These range from the preservation of existing retention areas to the restoration of existing facilities and the protection of objects. In the planning process, these measures were coordinated with ecological objectives in order to use synergies.
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 a migrate again, numerous measures to improve river continuity were defined on the Pielach.
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. A wide range of the proposed measures focus on improving the morphological conditions of the water bodies. These measures also partly support the objectives of flood risk management.
Measures to improve the sediment balance
A well-functioning sediment balance is of decisive importance for both, the flood risk management and the river ecology. If, for example, accumulations of bedload occur at narrow points in settlement areas, floods can occur. However, with interventions like for example dredging, the sensitive ecosystem and aquatic life will be disturbed. For this reason, measures to establish a balanced sediment budget were defined in the GE-RM Pielach.
Example of a concept for measures: Albrechtsberg an der Pielach and Loosdorf
The figure shows an example of a section of the concept of measures from the GE-RM Pielach for the area of Albrechtsberg an der Pielach and Loosdorf.
The concept of measures provides for different measures to reduce the flood risk and to improve the river ecology. The focus is on flood protection and river development in the Loosdorf-Albrechtsberg area with a broad bundle of measures.
In addition, the concept for this area includes
- the restoration of the passability of the mouth of the Mauerbach to reduce migration obstacles,
- flood protection for the Stöbermühle and Sitzenthal Castle, which can be achieved with local object protection measures,
- as well as the improvement of passability at the Neuhofner weir.
All details on the measures in the concept of measures of the GE-RM Pielach are presented in a comprehensive report, which is available for download (in German):
Fotonachweise:
Headerbild: EZB
Maßnahmen: Froschauer
Huchen und Uferschwalben: Adobe Stock
Weinburger & Haunoldsteiner Wehr, Pielach flussauf Mainburg & Sohlrampe Rennersdorf:
Johann Nesweda
Bewusstsein Bevölkerung & Abschnitt Weinburger Wehr:
Mostviertel Tourismus, weinfranz.at