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MERLIN restoration case studies: large transboundary rivers

August 18, 2022
The five large transboundary river sites in the MERLIN project: (4) Room for the Rhine branches, Netherlands; (7) Upper-Mid-Danube floodplain, Austria and Hungary; (8) Lower Danube floodplain, Romania; (9) Tisza River, Hungary; (10) Germany’s Blue Belt.

The MERLIN project focuses on 17 freshwater restoration case studies located across Europe.

These diverse sites and projects – including large rivers, small streams, peatlands and wetlands – offer researchers the opportunity to learn about best-practice approaches for restoration in contemporary landscapes. The project will explore how the impact of these projects contributes to the targets of the EU Green Deal.

Moreover, MERLIN is investing more than €10 million in these projects to help upscale their management through the use of nature-based solutions. It is intended that the progress made in bringing freshwaters back to life at these sites will help strengthen arguments for mainstreaming freshwater restoration across the continent.

This is the third of three articles introducing the 17 restoration case studies. This week, we focus on the five large transboundary rivers.

Floodplain rewetting along the Rhine Valley at Noordwaard, Netherlands. Image: MERLIN

Room for the Rhine Branches, Netherlands

Restoration of a resilient large river system for biodiversity, flood protection and navigation

Ongoing restoration work will be carried out across a 300km network of River Rhine branches throughout the Netherlands. These stretches of river – from the German border to the North Sea – have been heavily modified for centuries, with widespread weirs, embankments and groynes alongside intensive agriculture, mining and urban development.

This restoration of the Rhine branches follows decades of work through the Room for the River programme, which finished in 2018. Whilst significant progress has been made, climate change and channel erosion pose new challenges for restoration, which will be managed in the future through the Integrated River Basin Management programme.

Restoration measures, tailored to local conditions, include: floodplain restoration (e.g. through the removal of artificial channels and dikes); river channel restoration (e.g. the removal of polluted sediments); and connectivity restoration (e.g. the removal of barriers to the movement of water, sediment and fish). The overall aim is to create a more resilient large river system which balances conservation, flood protection, freshwater supply, navigation and recreation needs.

“A lot has been already been achieved by the Room for the River programme, but there are new challenges due to climate change, resulting in more extreme discharge patterns, and incised river beds requiring sediment management,” says Tom Buijse from restoration managers DELTARES. “Its successor is IRM for which the visionary plan should be ready by 2023. This will result in a follow-up programme for the coming decades.”

Find out more.

Floodplain reconnection at Liberty Island, Hungary. Image: MERLIN

Upper-Mid-Danube floodplain, Austria and Hungary

Reconnecting floodplains and tributaries to foster multifunctional landscapes

Two stretches of the Mid-Danube River in Austria and Hungary are being restored through a range of measures across its floodplains and tributaries. Whilst the sites are geographically independent, the upscaling of their restoration will be developed together.

In Austria, a stretch of the Danube in the Donau-Auen National Park will be managed towards more natural conditions by reconnecting floodplains to the main river, restoring riparian areas and removing artificial bank structures. It is intended that this range of adaptive restoration measures will help address multiple pressures such as riverbed deepening, the impacts of navigation, flood protection and land-use alterations.

In Hungary, a side branch of the Danube has been reconnected to the main river around the 4km-long Liberty Island. A key goal for this initiative has been to create a long-term, sustainable conservation model for white willow alluvial forests around the river. Restoration work has cleared invasive and non-native tree species around riparian areas, restoring water flows in the river side arm to allow the forest to flourish, even in times of drought.

“This case study represents the systematic process-orientated restoration of a whole large river stretch through adaptive management processes, to address multiple pressures,” say restoration managers from viadonau. “These are multifunctional floodplains, where restoration design should address the maintenance of a variety of ecosystem services and trade-offs including fishing, shipping, flood protection, forestry, agriculture and recreation,” add project partners from BOKU, Vienna.

Find out more.

Reconnecting floodplains along the Lower Danube in Romania. Image: MERLIN

Lower Danube floodplain, Romania

Reconnecting floodplains to boost biodiversity and buffer floods

Floodplain restoration is being upscaled at a series of sites along the Lower Danube River in Romania. As with much of the basin, the Lower Danube is highly regulated and altered by human construction, and as a result its huge former floodplain is largely disconnected from the main river. Intensive land use around the river has caused further habitat degradation, water and soil pollution, and water supply issues.

Restoration work seeks to reconnect the Lower Danube River with its floodplains as a means of boosting ecosystem health and mitigating flood risks. It is intended that more natural hydrological cycles will be created across wide areas of floodplain, wetland and polder, fostering a biodiverse mosaic of landscapes linked to the river. It is hoped that restoration work will, in turn, encourage sustainable grazing, fishery and aquaculture activities, alongside increased recreational and tourism use.

“The entire Danube river is regulated and long dike system protects the largest former floodplain area in the continent,” say restoration managers from WWF Romania. “The implemented measures use nature-based solutions to reconnect a part of the former floodplain with the Danube River.”

Find out more.

Wildflowers on the banks of the Tisza River, Hungary. Image: Györgyfi | Wikimedia Creative Commons

Tisza River, Hungary

Rewetting floodplains for sustainable farming practices

Floodplains on the Tisza River – a major tributary of the Danube – will be reconnected to the river and transitioned to sustainable farming systems. Like much of the Danube basin, the Tisza has been heavily modified by humans, and many of its former floodplains are dominated by intensive arable farming, which has dried out these formerly-wet landscapes.

Two floodplains in the middle Tisza River will be ‘rewetted’ through a series of floodways and flood risk reduction reservoirs. Initially implemented over 1,800 ha of floodplains, this work will increase water retention in the landscape, and create the conditions for sustainable floodplain farming practices.

It is intended that floodplain restoration will not only increase biodiversity and buffer flood waters, but also help foster economically-viable land-use systems around the Tisza. It is hoped that this work could be upscaled to over 150,000 ha of former floodplain landscapes along the Tisza basin.

“This case study presents real integrated solutions for flood risk management, water scarcity in agriculture, biodiversity loss, and climate adaptation,” say restoration managers from WWF Hungary. “It offers new economic and social opportunities for local communities, and for the cooperation of stakeholders.”

Find out more.

Historic buildings on the River Lahn, part of the national Blue Belt restoration project. Image: Living Lahn project

Germany’s Blue Belt

Renaturalising a major network of German rivers and floodplains

This ambitious national project seeks to restore around 4350km of rivers and 240,000 ha of their floodplains across Germany. The Blue Belt initiative began in 2019, and aims to renaturalise a huge network of federally-managed waterways, whilst at the same time maintaining their commercial navigability for boat traffic.

Most of the Blue Belt network – which includes major rivers such as the Rhine, Elbe and Weser – is heavily modified, with altered water flows, channel structure and degraded water quality. Floodplains across the network are often subject to intensive urban and industrial land use.

It is intended that renaturalisation of the banks and floodplains of this national river network will create significant new biodiversity habitat and offer new opportunities for tourism and recreation. Restoration work in the Blue Belt initiative seeks to foster a major new biotope network along Germany’s waterways.

“This project aims to ecologically restore functional river landscapes throughout Germany, but at the same time not to set aside commercial navigability,” say restoration managers from the Federal Institute of Hydrology, Koblenz. “Renaturalised federal waterways and their floodplains will form an important part of a biotope network and help to preserve water and floodplain species and their habitats. As a result of this a significant number of ecosystem services are generated, sustained or even enhanced.”

Find out more.


This article is supported by the MERLIN project.

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