River restoration and biodiversity

Rivers are important habitats for a large variety of animals and plants. Fish, amphibians, birds, insects, invertebrates, and reptiles live in rivers, or find their food there. Rivers play a vital role in connecting habitats, and their value to plants and animals extends far beyond the surface area they cover. This habitat connectivity role functions both between upstream and downstream areas, and by connecting both sides of river banks. This necessitates an approach to management that looks at the river basin as a whole rather than just taking into account the river itself.

Restoring natural functions

Aquatic biodiversity can only thrive in irregularly shaped river beds and river banks, where fish, amphibians and insects can hide from predators. Fish life and other aquatic flora and fauna need natural (ground)water flows within river banks and connectivity of habitats within the wider surroundings for their survival. Natural water flows also promote biological purification processes that contribute to cleaner water. This is important both for human use and for wildlife.

River restoration contributes to biodiversity by restoring ecosystems and ecosystem processes that are heavily modified. Physical restoration works include re-meandering (i.e. bringing back the curves of a natural river), creating green-natural river banks where previously banks were encased in concrete, and fish passes that enable the migration of fish past sluices, dams, and other obstacles.

Climate change adaptation

Climate change may impact aquatic biodiversity by reducing flows, increasing periods of drought and flood events, and warming rivers. River restoration can help support the adaptation of biodiversity in several ways, including: upstream wetland restoration and managed realignment to help increase water storage, planting of riparian trees in order to provide shade and reduce water temperature, and the removal of obstructions to increase connectivity and open up upstream or downstream habitat for migratory fish.

Moreover, through its contributions to maintaining and improving conditions for biodiversity, river restoration can be a powerful tool for achieving the objectives of the Habitats and Birds Directives, and the Water Framework Directive.

Featured Case

Vreugderijkerwaard

The river foreland Vreugderijkerwaard (on the IJssel river, near Zwolle, The Netherlands) has unique biodiversity, and is now considered one of the most valuable floodplains in the Netherlands.

The area was once affected by human activities such as navigation and silt removal, but now a restoration project managed to reduce flood risk whilst improving conditions for nature and navigation at the same time. The area is now again home to rare species of waterplants, including loddon pondweed and claspingleaf pondweed. In the wintertime thousands of white-fronted geese visit the area, and stilts such as plovers and ruff live here almost year round. Other local birds include the avocet, tern and brown kite.

 

From 1999 until 2003, a joint project between (a.o.) the Ministry of Nature, Rijkswaterstaat, local governments and Natuurmonumenten ran to improve conditions for this important floodplain. The main measures taken were the digging out a side channel of about 2 km long and reconnecting the bypass with the main river IJssel. The involvement of different levels of government ensured that various interests were represented adequately in this project.

Apart from the hydraulic requirements needed for more discharge capacity during peak conditions to prevent high water levels, enhancing the quality of wetlands and natural floodplains was one of the main objectives. Restoration of specific habitats for aquatic and (semi) terrestrial species of flora and fauna was a specific goal.

Galloway cattle and horses have been introduced in the area for vegetation management. These make sure that tree and shrub growth is kept within bounds, so the landscape maintains its open character. This is beneficial for the particular species that occur here, but also allows for high levels of excess water discharge, which serves flood management objectives.

Recent monitoring of the results showed an increase of rare submerged plants that are characteristic for streaming lowland rivers. Also, the value of the area for birds has been improved by the project. You can find more information about the Vreugderijkerwaard on the RESTORE River Wiki.

RiverWiki Case studies

For more case studies, visit our RESTORE case studies WIKI.

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