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MERLIN restoration case studies: small streams and basins

August 4, 2022
The six small streams and basin sites in the MERLIN project: (2) Basque streams; (11) Emscher catchment; (13) Sorraia catchment; (15) Tzipori catchment; (16) Scheldt catchment; (17) Forth catchment.

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 explore best-practice approaches for restoration in contemporary landscapes. The project will document 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 restoration 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 second of three articles introducing the 17 restoration case studies. This week, we focus on the six small streams and basin sites.

River barriers on the Deba River, Spain. Image: MERLIN

Basque streams, Spain

Reconnecting a heavily altered river through barrier removal.

A series of dams on the 60km-long Deba River in Spain will be removed to allow water, fish and sediment to move freely along its course. The local region of Gipuzkoa has a long history of industrial and urban development, and as a result the Deba’s channel is heavily altered. Many of the built obstacles along the Deba are now either obsolete or disused, yet they continue to block the free movement of water and fish.

Restoration work aims to reconnect the Deba River by removing ten dams along its course. It is intended that this work will restore more natural flow conditions in the river basin, whilst also supporting populations of migratory fish such as trout and eels, which migrate upstream to spawning grounds. It is also hoped that dam removal along the Deba will help restore habitat for wildlife.

“A key objective is to promote environmental education and nature-based solutions as restoration policies,” say restoration scientists from the University of the Basque Country. “Stakeholder interaction is being promoted, connecting local communities, institutions and governments.”

Find out more.

Wildflowers blooming on artificial dikes along the Emscher River. Image: MERLIN

Emscher catchment, Germany

Restoring riverbank habitats for biodiversity and recreation.

The Emscher River and its tributaries in Northern Germany have been heavily altered over many years. Urban and industrial development in the Emscher catchment has left much of the river flowing through concrete channels fragmented by weirs, culverts and artificial pumping stations. Cut off from its natural floodplains, the Emscher has been heavily polluted for decades as a result of sewage overflows and industrial run-off.

The MERLIN project will help restore meadow grasslands along riverbanks throughout the Emscher catchment to provide new habitat and recreation areas. These activities will help boost urban biodiversity in the catchment, and will complement wider river restoration measures being undertaken in the region. The MERLIN project will also help foster more participatory water management – for example through citizen science initiatives – and explore synergies between water management and environmental restoration.

“The Emscher restoration is, among other drivers, triggering the structural change in the region with the aim of ecological, social and economic sustainability,” say restoration managers from Emschergenossenschaft. “Nature-based solutions are being implemented in the urban areas to enhance climate regulation and adaptation, improving urban climate and the attractiveness of the cities, and thus, enhancing quality of life.”

Find out more.

Removing invasive water hyacinth in the Sorraia catchment. Image: MERLIN

Sorraia catchment, Portugal

Reconnection of floodplains and water flows through ‘blue-green’ restoration.

Rivers and floodplains across the Sorraia catchment in Southern Portugal will be restored using measures which improve water quality, boost biodiversity and encourage natural water flows. The Sorraia River and its tributaries are vulnerable to drought, as a result of a Mediterranean climate compounded by irrigation, flow regulation and damming. There are many permanent barriers such as weirs throughout the basin, which provide obstacles to fish migration. In the lower basin, much of the river system has been deepened and connected to irrigation channels. Agricultural activity also brings water quality issues due to nutrient and pesticide pollution.

Restoration in the Sorraia basin seeks to improve ‘blue-green’ connectivity between the river and its floodplains. Strategies include restoring riparian vegetation along river banks and the removal of exotic invasive plants such as water hyacinth and Brazilian milfoil. Other innovative nature-based solutions to be applied in the catchment include the creation of farm ponds, forest islands and ‘pollinator hotels’ to help boost floodplain biodiversity. It is intended that this ‘blue-green’ landscape restoration will also help reduce nutrient and sediment runoff and reintroduce natural water flow dynamics. Fish passes will also be constructed at weirs and river crossings to reconnect migration corridors.

“The case study has the ambition to quantify the importance of greening in the landscape, especially in agricultural landscapes,” say restoration managers from the University of Lisbon. “Both the National Environmental Authority APA and the National Agriculture Authority are part of the Advisory Committee of the Project, and The Farmers Association is a partner. The results are expected to have impacts that could feedback at the international policy level.”

Find out more.

Multiple land uses across the Tzipori catchment. Image: MERLIN

Tzipori catchment, Israel

Floodplain restoration and sustainable agriculture across an entire river basin.

The Tzipori River in Israel is fed by natural springs in the Nazareth Hills, and flows 32km through an intensively cultivated catchment to the Mediterranean Sea. The river is subject to a number of ecological stressors including water abstraction for agriculture, channel modification for flood protection, effluent and sewage pollution, and heavily agricultural land-use.

Restoration of the Tzipori catchment – which covers around 300km2 – centres on floodplain restoration, the creation of natural flood retention basins, and the transition to sustainable agricultural practices. It is intended that restored wetlands, floodplains and riparian vegetation will help naturally reduce flood risks, boost biodiversity, improve water quality and provide new opportunities for ecotourism.

“The restoration plan for the Tzipori takes a broad and in-depth ecological and hydrological perspective, accounting for the interfaces of the river with agriculture, urban spaces, and the open, natural landscapes along its entire length,” say restoration managers from Tel Aviv University. “The implementation of this plan, leading to rehabilitation of the entire river through a holistic river-basin approach, is considered a breakthrough in the field of river rehabilitation in Israel.”

Find out more.

Small stream in the Scheldt catchment. Image: MERLIN

Scheldt catchment, Belgium

Stream restoration for biodiversity habitat and flood protection.

An area of the upper Scheldt River basin around Zwalm in Belgium will be restored through a range of measures aimed at improving biodiversity habitat and water quality and reconnecting fish migration routes. The 355km long Scheldt River flows through France, Belgium and The Netherlands to the North Sea. Its upper reaches consist largely of small brooks, which are heavily impacted by untreated urban wastewater and agricultural pollution.

Restoration work through MERLIN seeks to restore riparian and fish spawning habitat along the upper catchment. Barriers to fish migration will be removed, and fish passes equipped with new online monitoring technologies will be installed to improve the connectivity of the catchment. Advanced new wastewater treatment plan and sewerage systems will be installed to help reduce the environmental impacts of pollution on the upper catchment streams. Water buffer basins along catchment floodplains will help reduce flood risks by slowing the flow of heavily rainfall.

“This project shows that ecological, economic and social aspects of restoration can be optimised in a smart manner, even over large spatial areas in densely populated areas with very high industrial and agricultural activities,” say restoration managers from Ghent University.

Find out more.

Stream dynamics in the Forth catchment. Image: MERLIN

Forth catchment, Scotland

River restoration in a post-industrial landscape for flood risk, biodiversity and socio-economic benefits.

Restoration work across the Forth catchment in Central Scotland includes both peatland and stream environments. Stream restoration in the catchment will include upscaling work being undertaken on the Allan Water, a tributary of the Forth. Allan Water (like other rivers within the Forth basin) is liable to cause flooding in downstream urban areas as a result of physical modifications to the river and its disconnection with floodplains.

Restoration work through MERLIN seeks to restore connections between the rivers and their floodplains on the Allan, Forth and Teith, to contribute to natural flood management and the restoration of valuable wetland habitats. Measures include placing large woody debris in the river channel and removing sections of engineered bank protection. Rivers will be reconnected to their floodplains through the removal of embankments and the restoration of stream channels, together with riparian tree planting. Through these works, restoration managers hope to create a more natural meandering river course surrounded by biodiversity-rich habitats. It is also intended that this work will help buffer flood risks, store carbon, and help boost local communities.

Restoration of these rivers in MERLIN is undertaken in partnership with The Allan Water Project Steering Group and others, which engages with landowners to support sustainable land management practices.

“The Forth Valley provides a rich and diverse landscape with a wide range of ecosystem services that have been impacted by centuries of mining, industry and urban expansion that along with poor management has compromised the natural assets of soil, water and air and includes areas of significant economic deprivation,” say restoration managers from the University of Stirling. “Despite this, the diverse landscape, interconnected with rivers, lakes, estuary and coastal environments presents many of the solutions required to support a smooth inclusive and just transition to a net zero economy, whilst mitigating against the extremes of climate change.”

Find out more.


This article is supported by the MERLIN project.

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