Green infrastructure can help protect river banks, reduce flow speeds, is often cheaper than conventional river engineering and provides multiple benefits, according to a new ebook from HR Wallingford.
Together, the ebook says, these are the critical success factors that river engineers can use to overcome the procedural and technical barriers preventing the use of GI approaches in river engineering schemes.
Traditionally, river engineers have used 'grey' infrastructure to manage flood risk. Increasingly, of course, natural flood management techniques are used, working with the natural processes of the river floodplain.
However, HR Wallingford's new ebook 'Green approaches in river engineering: Supporting implementation of Green Infrastructure' looks at the intermediary 'green to grey' stage between NFM and traditional concrete engineering.
In this context, green infrastructure (GI) includes measures that use vegetative materials such as willow spilling; green-grey measures such as artificial mattresses to provide structural stability to a green measure; grey measures such as rock rolls and geotextiles that used in situations where there is instability; and associated river management techniques such as meander restoration and bank regrading.
Commonly cited objections to the use of GI in river schemes include lack of evidence-based decision-making, risk aversion, resistance to innovation and the perception that GI has a higher risk of failure.
The ebook sets out how river engineers can overcome these obstacles by identifying and communicating GI's critical success factors. These factors are, the ebook says, infrastructure performance, lower costs and multiple benefits.
On performance, there is evidence GI is effective in protecting the bank and reducing flow speeds under a range of flow conditions. Furthermore, GI can be combined in existing schemes and with grey approaches, and value and function may increase over time.
GI approaches are often associated with lower capital costs than conventional solutions. They are also often eligible for funding from a wide range of public subsidies. In general, GI approaches may have the lowest whole-life costs, as well as being more cost-beneficial because they can deliver greater benefits.
GI approaches can also provide additional benefits beyond flood risk reduction. These include improving wildlife, fish spawning habitats and water quality; helping to restore natural processes; better integration into the natural landscape than grey solutions; improving the recreational value of the river; and promoting commnity engagement.
Download the ebook 'Green approaches in river engineering - supporting implementation of Green Infrastructure' here.