Functioning and measures

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The Marchfeld protective dam was built in the 19th and 20th centuries as a homogenous dam (= dam consisting only of earth material). Despite regular maintenance and renovation measures, the dam has been so badly damaged over the years by recurrent floods that a comprehensive general renovation including adaptation to the state of the art is now necessary.

The measures in detail

Dam rise, graphic — Dam rise, source: viadonau

Raising the dam

The dam geometry is adapted and the dam is raised by means of earthworks. To raise the dam, the existing humus layer or road structures are removed and the existing embankment fill is stepped down. The new profile cross-section of the embankment is formed with fill material. Finally, the humus layer or the path structure is restored.

dam sealing wall graphic — Dam sealing wall , source: viadonau

Sealed dam wall

The dam cut-off wall is constructed using proven geotechnical methods, such as deep soil stabilisation. It runs along the dam axis and extends at least one metre into the groundwater layer. In the event of a flood, the cut-off wall prevents the dam body from seeping through and extends the path of the water as it seeps into the dam.

Avoidance of a hydraulic fracture, graphic — Avoidance of a hydraulic fracture, source: viadonau

Measures to prevent hydraulic ground failure

The stability of the dam is crucial for its protective function. Gravel columns at the landside dam base connect the groundwater body with the ground surface. As the gravel columns thus pass through the relatively impermeable top layer, the uplift resistance of the top layer is ensured. An alternative to this is the use of ballast fill (coarse aggregate, stone throw) on fleece at the landside dam base. These counteract the uplift from the subsoil with their weight.

Protective strips

In the event of a flood, roots growing in the dam body can contribute to internal erosion and ultimately to dam failure. The protective strips are therefore primarily intended to ensure that the dam base and subsequently also the dam body remain as free of roots as possible. In addition, the strips serve as so-called manipulation areas for ongoing maintenance and upkeep work. They are also important for monitoring the dam in the event of flooding and for dam defence measures.