Green infrastructure: supporting green river engineering

The green infrastructure (GI) network is made up of natural and semi-natural features that connect and run through our urban spaces. Rivers form a key part of this green network, and GI approaches can be used to help conserve and restore these natural features by improving water quality, morphology and natural habitats.

GI approaches strengthen the functionality of river ecosystems by greening new and existing river infrastructure. They also help compliance with the environmental aspects of the Floods and Water Framework Directives. However, despite these obvious benefits, a number of obstacles exist that prevent green infrastructure approaches from being used as part of river engineering schemes. These often softer approaches can be perceived as having higher risk of failure, which is possibly partly attributed to a lack of design and maintenance guidance available to support their use. It has also been previously unclear to stakeholders how to demonstrate and communicate the multiple benefits of GI. Three actions were identified in this project as essential to overcome these barriers:

1. gathering existing guidance and literature to provide sound arguments as well as advanced, technical knowledge to promote the informed selection of Green or Green-Grey solutions in river engineering;
2. compiling and communicating a series of case studies that provide reliable evidence on key aspects of GI implementation, including constructability, engineering performance, environmental functions and social benefits; and 
3. identifying critical success factors (motivation, engineering performance, costs and ecosystem services) and assessment of their impact on decision making. 

The above actions ultimately led to a decision support framework at two different levels:

1. the Business Case, which provides arguments to support the decision to implement a GI approach,
2. the Technical Support, which provides the technical information base from which to select an appropriate Green or Green-Grey measure or technique.

The work was carried under a NERC-funded project (Natural Environment Research Council) led by HR Wallingford.

Partners included the River Restoration Centre, Environmental Policy Consulting, CIRIA, University of Liverpool and University of Nottingham.

The project was driven by the needs of the Environment Agency, Natural Resources Wales, the Welsh Local Government Association and Natural England.