Coastal defence

Information provided by Second World War Coastal Defence Battery, Battery Gardens, Brixham, South Devon, England.)... 

In addition to providing a valuable sea defence, intertidal sediments offer an important habitat for wildlife, food and recreation. The very nature of intertidal areas has left them relatively undisturbed by human activity compared to inland areas. This coupled with the rich food supply in the muddy sediments means that many intertidal areas are now very important wildlife sanctuaries and nursery grounds for fish and invertebrates (Adam, 1990). Thus, for example, up to 12 million birds of 50 different species live for at least part of the year on the vast shallow water or intertidal muds of the Wadden Sea off the north Dutch and German coast (North Sea Task Force, 1993). Beside these quantifiable environmental roles as wildlife habitats and coastal defences, these intertidal areas have an intrinsic beauty that has always attracted people. 

It is possible that more than one metric contributes to die poor status. In lakes it is common for quality elements of phytoplankton, macrophytes and fish to fall short of the quality criteria. In rivers, macrofauna and fish are likely to have inadequate scores. In both situations the steering factors form a complex. In the example of lakes, this is known as a eutrophication complex. In rivers it is caused by canalisation and normalisation. And, third, the complex causing an inadequate score for macrofauna and fish in the metric for transitional waters is called coastal defences. 

John Gross Barnard graduated in 1833 from the US Military Academy, West Point NY, and was posted then as second heutenant in the US Army Corps of Engineers. He served on garrisons and fortifications, participating in the construction of coastal defences at Fort Columbus/Fort Jay, Fort Hamilton and Fort Wadsworth in New York City NY, New Orleans LA,... 

Mai Van, C., van Gelder, P.H.A.J.M. and Vrijling, J. K. 2006. Safety of coastal defences and flood risk analysis. Safety and Reliability for Managing Risk, ISBN 13 978-0-415-41620-7, Taylor Francis/Balkema, Leiden, The Netherlands, Vol. 2, pp 1355-1366. 

The Environment Agency uses its framework contractors and specialist subcontractors to undertake coastal defence works. In total there are probably only a dozen companies undertaking coastal engineering work for the Environment Agency. Agency staff consulted eonsidered that this helps to maintain high competence levels within the eontraetors they use. It is the Agency s stated policy objective to achieve a position of zero reportable construction incidents and to be considered to demonstrate best practice as a client. 

The coastal zone is, by its very nature, an environment where it is difficult to totally separate the construction process from the public (Figure 6.3) and other users such as nshcrmcn. By their very nature, the high costs associated with coastal defence projects can normally only be justified economically where there arc significant assets at risk, with corresponding numb s of people using the area. 

Ford, D C. and Williams, P.W. 2006. Karst Hydrogeology and Geomorphology. Wiley, Chichester. French, P.W. 2001. Coastal Defences Processes, Problems and Solutions. Routledge, London. 

Hooke, J. 2000. (Ed). Coastal Defence and Earth Science Conservation. Geological Society, London. 

Clayton, K.M. 1990. Sea level rise and coastal defences in the United Kingdom. Quarterly Journal Engineering Geology, 23, 283-288. 

DELOS, Environmental design of low crested coastal defence structures. Fifth Framework Program of the EU, Contract no. EVK3-CT-00041. www.delos.unibo.it. 

An example of these sediment transport patterns can be seen in Fig. 22.14, which consists of a bottom survey carried out in Lido di Dante (Ravenna, Italy). The coastal defence in this site is composed of three groynes, two detached zero freeboard LCBs with a protected gap in between, and two low-crested coimectors from the northern and southern groynes to the LCBs (Zyserman et Zanuttigh ). Deep crescent-shaped erosion areas at about 70 m from the two barrier roimdheads can be recognized, which have a maximum depth of 1.5 m, a length of 150 m, and a width of 50 m. A flame-shaped erosion hole, 1.0 m deep, 120 m long, 50 m wide, is present seaward of the central gap, due to the rip current concentration and intensity. Deposition occurs seaward the detached LCBs, due to wave breaking at the offshore LCB slope and to return currents from the roimdheads. 

B. Zanuttigh and A. Lamberti, Experimental analysis and numerical simulations of Waves and current flows around low-crested coastal defence structures, J. Wat., Port, Coastal and Ocean Eng. 132(1), 10-27 (2006). 

DEFRA/Environment Agency Flood and Coastal Defence R D Programme — Risk, Performance and Uncertainty in Flood and Coastal Defence, Report FD2302/TR1, HR Wallingford Report SR587 (2002). 

E. C. Penning-Rowsell, C. Johnson, S. Tunstall, S. Tapsell, J. Morris, J. Chatterton, A. Coker and C. Green, The benefits of flood and coastal defence Techniques and data for 2003, Flood Hazard Research Centre, Middlesex University (2003). 

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