LAFNITZ
Description of the project area
The project area comprises the river Lafnitz with a total length of approximately 110 km. The Lafnitz originates in Styria above “Lafnitzeck” and forms the Styrian-Burgenland border over long stretches. South of the municipality Fürstenfeld it flows into the Raab, which then runs in a large curve from the East Styrian Hills towards the Hungarian Plains. The catchment area of the Lafnitz is 1 994 km². During a 100-year flood event (HQ100), the flow at the mouth of the river is about 900 m³/s. The largest tributaries of the Lafnitz are the rivers Safen, Rittschein and Feistritz.
The river’s gradient successively decreases from 15 ‰ in the upper reaches (Waldbach estuary) to 6 ‰ in the middle reaches and 1,2 ‰ in the lower reaches.
The character of the river also changes continuously. In the upper reaches, the Lafnitz quickly develops into a torrent due to inflowing spring streams. It then flows through relatively straight, deeply incised valleys. After leaving the crystalline basement (Rohrbach-Lafnitz), the Lafnitz runs as an increasingly meandering river into the lowlands.
In the border section between Burgenland and Styria the Lafnitz remained mostly unregulated and is therefore important from a natural and river morphological point of view. Due to the still existing natural river dynamics (“dynamic equilibrium”), the riverbed, banks and meadows are naturally subject to constant changes. These dynamics become particularly evident, where the political boundaries deviate from the actual river course of the Lafnitz.
Another specific feature of the river is the fact that in the middle and lower reaches the Lafnitz does not flow at the lowest point of the valley – it forms a naturally dammed river. The decreasing gradient and bank vegetation lead to a reduction of the flow velocity. This causes solid and suspended matter to deposit, forming embankments and raising the riverbed. These embankments drop steeply towards riverbed, while they are rather flat towards the floodplain.
LAFNITZ
Description of the project area
The project area comprises the river Lafnitz with a total length of approximately 110 km. The Lafnitz originates in Styria above “Lafnitzeck” and forms the Styrian-Burgenland border over long stretches. South of the municipality Fürstenfeld it flows into the Raab, which then runs in a large curve from the East Styrian Hills towards the Hungarian Plains. The catchment area of the Lafnitz is 1 994 km². During a 100-year flood event (HQ100), the flow at the mouth of the river is about 900 m³/s. The largest tributaries of the Lafnitz are the rivers Safen, Rittschein and Feistritz.
The river’s gradient successively decreases from 15 ‰ in the upper reaches (Waldbach estuary) to 6 ‰ in the middle reaches and 1,2 ‰ in the lower reaches.
The character of the river also changes continuously. In the upper reaches, the Lafnitz quickly develops into a torrent due to inflowing spring streams. It then flows through relatively straight, deeply incised valleys. After leaving the crystalline basement (Rohrbach-Lafnitz), the Lafnitz runs as an increasingly meandering river into the lowlands.
In the border section between Burgenland and Styria the Lafnitz remained mostly unregulated and is therefore important from a natural and river morphological point of view. Due to the still existing natural river dynamics (“dynamic equilibrium”), the riverbed, banks and meadows are naturally subject to constant changes. These dynamics become particularly evident, where the political boundaries deviate from the actual river course of the Lafnitz.
Another specific feature of the river is the fact that in the middle and lower reaches the Lafnitz does not flow at the lowest point of the valley – it forms a naturally dammed river. The decreasing gradient and bank vegetation lead to a reduction of the flow velocity. This causes solid and suspended matter to deposit, forming embankments and raising the riverbed. These embankments drop steeply towards riverbed, while they are rather flat towards the floodplain.
Hot Spots & Highlights
The Lafnitz and adjacent areas, which are designated for passive flood protection to the extent of around 300 hectares, have been declared as NATURA 2000 protected areas. For another 400 hectares of agricultural land management restrictions can be imposed with possible one-time compensation. In spring 2002, the Lafnitztal valley was declared a RAMSAR area. In addition, the Lafnitz serves as a reference river for the river type “near-natural lowland rivers” in the municipalities of Altenmarkt and Fürstenfeld in accordance with the EU Water Framework Directive.
Two cross-border LIFE-Nature projects, supported by the federal states of Styria, Burgenland and Hungary, aimed to eliminate existing deficits on the Lafnitz river in accordance with the EU Water Framework Directive. For this purpose, longitudinal continuity interruptions (obstacles for upstream or downstream fish migration) were removed, habitats were re-connected and the natural river landscape was secured.
Need for action
In the 1960-1980s, the Lafnitz valley was repeatedly hit by catastrophic floods. As a result, four water boards were founded to implement flood protection measures. The activities concentrated on the affected settlement areas of Rohrbach a.d.L., Lafnitz, Wörth, Neudau, Rudersdorf and Dobersdorf. Initially, so-called linear regulation works were implemented in combination with retention dams and flood spillways. Where a large-scale reduction of flood peaks was not possible, but suitable valley formations were found, flood retention systems were built. Nevertheless, there is still a great need for action to protect settlements in these areas.
From an ecological point of view, there is a considerable need for action due to the existing water diversions, sediment input from agricultural land and a dramatic decline in fish biomass. Several stretches of the river Lafnitz fail the objective of good ecological status.
Goals
The River Development and Risk Management Concept (GE-RM), which will be elaborated and coordinated by the Federal River Engineering Administrations of Styria and Burgenland on a supra-regional basis, is intended to define future flood protection engineering and measures for improving river ecology – in consensus with existing uses – in an integrative participation process.
Building on this, pilot measures will be implemented in the frame of the IRIS-Project. In the Styrian municipality of Neudau, measures for flood protection will be implemented in combination with the improvement of the Lafnitz habitat. In the Burgenland municipality of Königsdorf, which is heavily used for agriculture, biological diversity will be increased by re-connecting the Lafnitzt with several small sidearms in the estuary area of the river Rittschein.
Outlook and time plan
By the end of 2021, the “Lafnitz River Development and Risk Management Concept ” will be finalised. Involvement of stakeholders and the public in the planning process is planned in order to achieve the best possible identification and acceptance with the proposed measures. Once the GE-RM concept is in place, detailed projects will be developed for pilot measures to be implemented by mid-2026.
