Estuary Edges: Guidance on Ecological Design of Tidal River Edges

In 2007 the scattered guidance that existed on the ecological design of the margins of our non-tidal rivers in the UK encouraged an outdated approach relying on over-engineered designs. Whilst such designs generally achieved flood risk management objectives, they provided few if any other benefits e.g. in terms of biodiversity or landscape enhancement. Moreover, since the late 1990s several innovative approaches to ecological design of tidal river edges had actually been applied in real projects in the UK, especially along the Thames and Severn Estuaries; but nowhere was this information compiled and organised in a systematic way to provide a proper tool for how to approach tidal river edge design.

The Environment Agency (EA), contracting through Thames Estuary Partnership (TEP), therefore issued a research project tender to do exactly that. Biodiversity by Design won the project in open competition.

Biodiversity by Design formed a consultancy team comprising Salix River and Wetland Engineering, Beckett Rankine Marine Engineers and Gary Grant; and then led the production of the guidelines which were published in 2008 (available from the website of the European Centre for River Restoration. See: http://www.ecrr.org/Portals/27/Publications/Estuary%20Edges%20-%20design%20advice.pdf).

We compiled case study material through desk research and field visits. Several of the examples were taken from projects designed or implemented by Biodiversity by Design or Salix. We led several workshops with the TEP/EA team to discuss the content and structure of the guidance over the study period.

The guidance sets out the basic legal and policy framework (now in need of updating) as well as the philosophy that should be applied to tidal river edge design such that the minimum amount of non-biotic elements should be included in the design of any tidal river edge in order to meet flood risk management functions reliably. The factors that need to be considered are set out including the approach to risk. River edge designs are categorised into bioengineered, bio-technically engineered and fully structurally engineered categories. The last category includes ecologically enhanced vertical intertidal walls (e.g. vertical beaches). Recommended monitoring approaches are described. The guidance explains the variety of ecological, social and economic benefits that can arise from such approaches, most notably the restoration of very important natural capital that has been lost from our estuaries, especially in urban areas.