Taking a holistic approach to watercourse restoration

Turning an ecological vision into a successful restoration project requires the right engineering approach

When rivers and streams are realigned or restored to a more natural state, the task is not simply to create a new course in the landscape. A highly complex ecosystem is being created, and in its critical early phase it often requires protection and technical support in order to function dynamically over the long term. Restoration does not mean that all functions will automatically re-establish themselves.

Once a watercourse has been altered, for example through river realignment or widening, very practical questions quickly arise: How can the bed be made functional again? How can newly formed banks be stabilised? And which additional measures are appropriate in sensitive areas?

In many projects, the bed is the critical element

If a watercourse bed is deepened, widened or newly created, the original low-permeability layer formed by colmation may be lost, either partially or completely. Some watercourses will seal themselves again over time; in other cases this is not sufficient or takes too long. The question then is how the bed can be sealed again while supporting the natural colmation process.

For such cases, Bentofix^® Green is suitable as a thin mineral sealing system. It is used in ponds, streams, ditches and rivers to support colmation and provide a sealing effect from the outset. In restoration projects, this is particularly relevant wherever a solution is required for bed sealing that fits naturally into the design while also remaining practical from a construction point of view.

• Reliable sealing: Hydraulic sealing performance immediately after installation, without lengthy compaction processes.
• Faster construction progress: Supplied in prefabricated rolls, the system reduces installation time compared with extensive earthworks and can also be installed within tight construction windows, for example during low-water conditions.
• Logistical advantage: Where conventional clay layers require numerous lorry movements and major excavation works, the thin system reduces transport effort and conserves on-site resources.

Practical example: flood protection and ecology in Brixen

The flood protection project in South Tyrol shows just how important the bed is in real projects. There, the bed of the Eisack river was reshaped in collaboration with the Office for Torrent and Avalanche Control of the Autonomous Province of Bolzano. As part of that modification, it was necessary to ensure that the hydraulic separation between river water and groundwater would remain effective over the long term. Bentofix^® Green liners with biodegradable* geotextile components were used for this purpose. The project is an example of how hydraulic, ecological and urban enhancement can be combined. The narrow construction window during low-water conditions also played an important role.

For planners, authorities and clients alike, this is a key point: restoration does not simply mean reshaping a watercourse. The underlying functional requirements must also be right.

Banks also need protection in the early phase

The riverbed alone is often not the whole story. Banks are remodelled, slopes are adjusted and marginal areas are reshaped. In the initial phase after construction, these areas are particularly sensitive: vegetation has not yet established itself, and rainfall or flow action can quickly lead to erosion.

Temporary erosion-control solutions made from natural materials help bridge the gap to long-term stability. Biodegradable* erosion-control mats can be used wherever banks and slopes along watercourses need temporary stabilisation until vegetation is able to take over that function itself.

Considering adjacent areas and vegetation

In many restoration projects, the scope does not end at the watercourse itself. Adjacent areas also influence how a measure develops. The challenges here include, on the one hand, the desired development of vegetation and, on the other, the protection of sensitive soils during the construction phase.

• Natural barrier against invasive species: Invasive plant species can hinder the intended development because they displace native vegetation and dominate sensitive areas. Targeted temporary covering with biodegradable* nonwovens can mechanically suppress problematic plant stands without chemical treatment.
• Low-impact access: Heavy machinery often has to cross sensitive floodplain soils to reach the work area. To protect the ground, these nonwoven materials can act as a separation layer for temporary access roads. Once the works have been completed, the temporary access route can be removed and any remaining material components biodegrade* under natural conditions.
  

This makes one thing clear: restoration does not consist of a single measure alone. In many cases, it is the interaction of several building blocks that makes a project coherent in practice.

Conclusion: restoration as a dynamic process

No two watercourse projects are the same. In some cases, the functionality of the bed is the main concern; in others, it is erosion control in the upper reaches or the management of invasive species in the floodplain. The key is to understand restoration not as a static structure, but as a dynamic process.

Anyone planning a river restoration or watercourse redesign project must bring together a range of boundary conditions. These include the type of watercourse, the subsoil and the hydraulic regime, as well as the ecological objectives and the economic considerations of the measure.

A technical discussion often helps to define the project components and challenges more clearly and to determine the next steps in a meaningful way. We would be pleased to discuss your project with you personally and to explore together which solutions may be suitable for the bed, the banks or adjacent areas.