Turning old into new: Leitha Gatten­dorf

What measures were implemented on the Leitha?

An old branch of the Leitha was reconnected from both sides. An inclined lateral dam with stone protection guides the water of the Leitha into the old arm and the bed of the Leitha was partially shifted into the course of the old Leitha. The banks were widened on both sides.

An island in the old river branch was reactivated in accordance with the historical model. Downstream of the island, the terrain on the inner bend was lowered up to the existing forest line; the embankment was only created directly in front of the forest line. The banks and the terrain here are extremely flat and are flooded even during small floods. Due to regular flooding, this area is constantly evolving as a result of the dynamic processes.

To protect important infrastructure ( roads) and to protect the low-flow line, 5 stone low-water groynes were constructed on the outer bank. Other smaller structuring measures in the water and planting on land round off the measure.

Up to a discharge of approx. 40 m³/s (corresponds to about HQ1, i.e. a flood that statistically occurs once a year), the water is directed exclusively through the “new” old branch. In the event of higher discharges, the water flows over the lateral dam into the preserved former culvert. If necessary, the culvert can be opened using a gate valve to take in additional water.

Why was the Leitha near Gattendorf revitalized?

The LIFE IP IRIS project aims to harmonize flood protection with ecological goals. This is achieved mainly through the use of nature-based solutions. The IRIS project therefore uses river revitalization measures to restore parts of rivers to their natural state. Along the Leitha, revitalization has restored some of the habitat that was lost due to river regulations in the 1970s. At the same time, the measures have improved flood protection.

Strong regulation and high proportion of residual water section

Once the Leitha formed meanders in many areas. However, due to intensive river regulation and straightening, these have now almost completely disappeared and with them many important habitats. In combination with the effects of power plant operation, a large number of ecological problems arise. At almost 50% of the total length, the proportion of residual water sections as a result of power plant operation is very high. Due to water diversions, low residual flows and natural seepage, some sections of the Leitha run completely dry at times. This is a major problem for many animals and plants. On the other hand, the flooded areas in the event of a flood are large due to the flat landscape, which also poses challenges.

More vitality for the Leitha

In order to revitalize at least part of the river, an old branch of the Leitha was reconnected. In this area, the Leitha can once again develop more freely. The natural processes along the river are creating a healthy and dynamic river landscape characterized by a wide variety of habitats.

Ecological goals and flood protection

The river morphology was improved by reconnecting the unspoilt old river branch from both sides. Dynamic processes such as erosion and sedimentation create a varied river in which deep pools and channels alternate with shallow fords. The different flow conditions create ideal habitats for juvenile fish, amongst other things.

On land, too, the combination of riparian forests and open landscape types provides a variety of different habitats in which numerous native animals and plants thrive.

The former cut-through of the Leitha remains as a side arm connected on both sides (not as a dry flood trough) and is connected to the Leitha via 2 dosing pipes. The water inflow can be regulated via gate valves and in the event of flooding some of the water can be collected. The reconnection of the old river branch therefore also has a positive effect on flood protection.