Urban River Restoration

Rivers in our Towns and Cities

People have traditionally settled next to rivers and estuaries. Over time this has transformed the natural environment into the towns, cities and ports we see today. Urbanisation comes at a cost to rivers – they have been heavily degraded to enable development, carry waste, supply drinking water and facilitate transport and industry.

Urbanisation affects a river in many ways:

physical structure: artificial walls replace reed beds and natural river banks, or in many cases the river is hidden underground
water quality: increased run-off from impervious surfaces such as roads, roofs and gardens, and contamination from industry discharges degrades water quality
ability to support wildlife: natural corridors, riparian zones and in-channel habitats are lost
removal of riparian vegetation: reduces organic input, habitat complexity, increases riverine temperature and reduces bank stability
Geomorphology: urban rivers lack the space to erode their banks and deposit sediment or connect to their floodplain, which leads to altered morphology. Bridges, pipes and other infrastructure alter the width and depth of rivers, and their courses are changed by straightening and bypassing
water quantity: decreased flow and reduced groundwater levels through abstraction and increased flow from surface run-off, increased frequency of floods and reduced infiltration
invasive species: urban areas often suffer from introduced non-native species that become dominant and cause damage to the environment.

These stresses make rivers less resilient to the effects of climate change. Current modelling for much of Europe predicts that winter rainfall will be more intense, leading to increased flooding and that summer rainfall will decrease with an increase in very hot summer days, leading to reduced water levels, making communities are less able to deal with an uncertain climate. (European Environment Agency, 2012)

Restoring Urban Rivers

The following approaches present the best ways of tackling the effects of urbanisation on rivers. There are also many techniques described in the How to pages:

Sustainable Drainage Systems

Hard surfaces prevent water from naturally draining through soil, resulting in increased floods, erosion, pollution and decreased habitat. Returning flows to a more natural state by reducing run-off from impervious surfaces is the simplest method of improving rivers. Sustainable urban drainage and green roofs are long-term approaches to managing surface and groundwater by reducing the rate and volume of run-off. They are extremely effective in new developments and preventing further degradation of urban waters. They can also benefit existing urban watercourses through retrofitting. More information can be found here:

The community for sustainable drainage
CIRIA
Background: The Green Roof Centre (UK)
Guidance: Green roof toolkit (Environment Agency, UK)
CABE Case-studies of Ekostaden-Augustenborg

Habitats

Simply removing hard riverbanks to increase riparian vegetation and habitat complexity can improve urban rivers and offer socio-economic enhancements as well (Techniques). Even where flow rates are not reduced, riparian plants can cool rivers, stabilise banks and offer shade to fish and animals. Hard surfaces in urban areas can limit the amount of riparian planting, but even small amounts on highly degraded sites can significantly improve biodiversity. Introducing gravel substrate in highly constrained locations can provide important linkages for wildlife moving between open space and more natural areas.

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Local Communities

More than 50% of people in the world now live in cities and more than 75% live near a river. Rivers are increasingly valued as part of the urban environment, rather than simply a means for removing waste water and rubbish. Successful urban river restoration is as much about establishing trust with local people as it is about improving flows and habitats. By informing people about the social and economic benefits of urban river restoration, as well as the ecological advantages, it is more likely that practitioners can include local priorities within a successful project.

Due to cost and limited space it can be challenging to undertake larger restoration projects in urban areas. However, even at smaller scales, making use of sites that are available, restoration can have a positive effect.

Case Studies

Sutcliffe Park
Isar in Munich
Seol
Ekostaden Augustenborg redevelopment project – see page 44 of guide
MayesBrook

The Benefits

Urban redevelopment is an opportunity to revitalise rivers and offers a variety of ecological and social and economic benefits including:

Improved flood management using more natural processes
Reduced likelihood of negative impacts caused by climate change through increased ecosystem resilience
Reconnecting people to the natural environment through urban regeneration
Better access for recreation and improved well-being
Enhanced habitats for wildlife.

Achieving these aims requires a new approach by integrating decision making across many sectors and adopting an ecosystem approach.

The publication ‘Rivers by Design’ outlines how to rethink the relationship between cities and rivers and improve on the old design approach of hiding rivers underground and behind walls. Instead, towns and cities are adapting to river dynamics, incorporating them into the built environment as habitat for plants and animals and as an oasis of nature for people.

For example, improvements to the River Isar in the city of Münich and in Lewisham (UK) provide increased access to recreation for large numbers of people and have revitalised the socio-economic vitality of these areas. See the case study and look at the social benefits pages for more information.

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