The use of ‘managed retreat’ in coastal engineering

Abstract

‘Managed retreat’ involves the deliberate breaching, removal or landward relocation of an existing tidal defence or coastal protection structure. Its use in coastal engineering is unquestionably controversial. Despite this, changes over the last decade in the approach to coastal engineering in England and Wales have ensured that consideration is given to managed retreat (together with other potential solutions) along all coastal frontages. Furthermore, where managed retreat is identified as the most technically justified, economically viable and environmentally acceptable option, it is now more frequently being selected as the preferred engineering approach to addressing coastal management problems. This paper discusses the role of managed retreat in coastal engineering, identifies the physical and technical situations to which managed retreat is best suited, describes general implementation techniques and methods for optimising scheme designs, and identifies reasons for the relatively conservative uptake of managed retreat in the UK to date. One such reason is identified as a lack of guidance concerning methods for assessing, during feasibility studies, the potential impacts associated with managed retreat schemes. The paper addresses this issue directly by additionally presenting a case study of two proposed managed retreat schemes located within the Tamar estuary in Cornwall, south-west England. The paper concludes that, in order to increase future uptake of managed retreat in the UK, there is a need for an improved mechanism for freeing up land to enable retreat to occur. This could include both improved compensatory remuneration for land and property owners, to make the managed retreat option more favourable, and improved links between coastal engineering and development control, to ensure that the potential for managed retreat is not negated by future land-use developments.