Successful Implementation of an Offshore Reef Scheme

The use of offshore reefs for coast defence has been questioned by several authors in recent years, predominantly due to concerns over the effects on adjacent beaches. Other concerns that are expressed in relation to offshore reef schemes are listed below : 1)The impacts on downdrift beaches are unpredictable and large; 2)Environmental impacts are adverse; and 3)Whole-life costs are high relative to the alternative defence options. This paper demonstrates the level of confidence that may be placed in generic outline design criteria, by reference to the Happisburgh to Winterton Sea Defence Strategy on the east coast of the United Kingdom. In addition, the paper presents the successful development of an outline design of reef geometry to detailed scheme design, using computational models to predict downdrift erosion effects. Observations of the actual downdrift beach response over a period of nine years are compared to model predictions. Given the nature of the Conference, no discussion of environmental impacts is presented, although increases in biodiversity and fish catches have been recorded in the vicinity of the reef scheme.