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1 Introduction
Enzo Pranzini and Allan Williams
The sea is all around us and brings to mind ‘Newton with his prism and silent face … voyaging through strange seas of thoughts, alone’ (Wordsworth, 1896, 61). The seas written about in this book may be strange or familiar, but the voyage across them to the European coastline has not been made by us alone, but together with a band of erudite and thoughtful companions. Coastal erosion and consequent deposition has been a natural process for aeons but sometimes human intelligence leaves a footprint on this landscape of transience and recurring cycles; frequently it is greed, when not ignorance, that leaves such landmarks. Beach erosion resulting from human intervention – the inevitability of human folly – is an example of the above.
Erosion is a generic term used to describe landform recession or lowering brought about by natural processes, e.g. water, ice, wind, all involving movement (Figure 1.1a) that is sometimes trigged or intensified by human action. Since prehistory, coastal areas favoured human settlements and, later, infrastructures protected these assets, as well as people, from erosion and flooding. For coasts to erode, more material has to be removed than supplied; consequently shorelines most susceptible to erosion are typified by soft or loose sediments, under high wave energy and sea level rise. However, in the past few centuries, anthropogenic influences have played a large part in this process. It is the increased erosion rate, which affects the coastal infrastructure (roads, buildings, etc.; Figure 1.1b), that usually necessitates an engineering solution, or management decision to do nothing and ‘let nature rule’. Coastal protection features associated with the above are all given greater depth in analyses within this book.
The causes of erosion are many.
Figure 1.1a Shore platform at Southerndown, Wales Figure 1.1b Coastal erosion, Menfi, Sicily, Italy Natural changes occur on many scales (long vs. short term) and are functions of, for example, sea level rise producing increased wave attack; climate change possibly resulting in more severe storms; water table rise as a result of higher rainfall; coastal geology (hard vs. soft rocks with the latter more easily removable); high energy sea states (wind/wave) and/or change in angle of dominant wave attack, which in turn influences the efficiency of longshore currents to remove/deposit material; subsidence; etc.
Anthropogenic factors are particularly effective when they reduce sediment input to a coastline. Some examples include: river damming thereby cutting off sediment that should reach the sea (Figure 1.2); increased changes in land practice, e.g. farmers leaving the land to work in a burgeoning tourist industry, thereby ensuring that previously farmed land reverts to its natural state (grass, shrubs, trees), which in turn cuts down sediment input to rivers and ultimately beaches. The above affect beach sediment budgets, which can be further changed by, for example, groin construction, piers, jetties or breakwaters, which interrupt alongshore sediment transport; construction of coastal defences – ‘coastal concretisation’ – i.e. seawalls, which prevent coastal retreat and reduce sediment input to the downcoast segments; seaboard deepening by dredging; wrong engineering practices; dune destabilisation; drainage modification.
It must be emphasised that erosion – and its counterpart, deposition – is a natural phenomenon and it is usually the accelerated rate of change imposed by man that causes anxiety. An introduction of a barrier between land and sea has been seen in many areas, not just in Europe but across the globe. Coastal areas have been exploited since time immemorial, in that early harbours utilised natural geographical features such as sheltered bays, lagoons, areas away from strong winds/seas, etc. Mediterranean harbour engineering (jetties and breakwaters) followed patterns set down by Egyptians, Phoenicians, Greeks, Etruscans and Romans, but with the exception of Vitruvius (30 BC), few sources exist in writing. Pre-Roman Mediterranean proto-harbours have been written about by Lehmann-Hartleben (1923) and little changed until Napoleonic times (Franco and Verdesi, 1993), so modern coastal protection could date from this era.
Figure 1.2 Monte Cotugno dam (Basilicata, Italy) is the largest earth dam in Europe, enclosing a large part of the Sinni river catchment area and triggering erosion of the Ionian coast (Upper photograph by A. Trivisani) So what is the length of the European coast, considering that each part is potentially subject to the erosion process? It is extremely difficult to measure an irregular feature, i.e. coastal length, as it is scale-dependent (Mandelbrot, 1967). The lengths given in Table 1.1 were obtained from the World Vector Shoreline GIS database at 1:250,000 km, using a single source, which used a constant scale; they are approximations, which must be used with caution (http://www.mrj.com). For the above reason, these figures give a value that can vary from the others given in this book, e.g. the 2,600 km for the Ukraine coastline (chapter 21), as well as the fact that coastal features are constantly changing through time because of erosion/deposition.
In this book, Bosnia and Herzegovina, Croatia, Montenegro and Slovenia have been considered as one entity – the Eastern Adriatic (with a coastal length of 6,021 km), Similarly the countries of Latvia, Estonia and Lithuania have been addressed as the Baltic States (with a coastal length of 3,378 km).
An EC (2004) project, which studied European coastal erosion levels, formulated four main recommendations:
1. Restore the sediment balance and provide space for coastal processes.
2. Internalise coastal erosion cost and risk in planning and investment decisions.
3. Make responses to coastal erosion accountable.
4. Strengthen the knowledge base of coastal erosion management and planning to coastal erosion.
With regard to the latter recommendation, findings suggested ‘a rating of European coastal regions according to their exposure to coastal erosion together with dissemination of best practice,’ i.e. what works/does not work (EC 2004, 36). The present book looks in detail at erosion issues associated with the many countries that constitute coastal Europe, together with the resulting engineering strategies introduced as possible solutions to the problem. Both ‘good’ and ‘bad’ practices are described in the various chapters. The authors are all key coastal research experts in their respective countries and present coastal erosion statistics and protection strategies (old and recent) that have been utilized in their countries. Work on coastal erosion and engineering structures has significantly developed over the past few decades and the 20 chapters covering 25 countries span the spectrum of coastal protection measures, from ‘hard’ to ‘soft’ engineering practices.
Table 1.1 Coastline lengths of the considered European countries (km) Source: Data are based on the World Vector Shoreline, United States Defense Mapping Agency, 1989. Figures were calculated by L. Pruett and J. Cimino, unpublished data, Global Maritime Boundaries Database (GMBD), Veridian–MRJ Technology Solutions (Fairfax, Virginia, January 2000)
Note: * not included in this database but obtained from authors.
Increased sea surface temperatures together with a sea level rise will probably result in more frequent and severe extreme weather events. Coastal storms will develop bigger waves than normal, which, together with surges, will inevitably result in increased coastal erosion rates and flooding of low-lying lands. After some 6,000 years of almost stable eustatic level, although locally glacio-isostasy and tectonics have played an important role, at the start of the nineteenth century this global phenomenon accelerated to 1.7–1.8 mm/yr (Gornitz, 2007). Throughout the nineteenth and twentieth centuries, global average sea levels have continued this acceleration to 3.1 mm/yr from 1993–2003 and it is further postulated that globally, sea level will rise a further 18–59 cm by the end of the twenty-first century (IPCC, 2007).
The scenarios described can on a global basis cause untold misery and death to many thousands of people, e.g. the catastrophic floods (Watersnoodramp), ‘flood disaster’, of 31 January to 1 February 1953, which killed 836 persons in the Netherlands, 307 in the UK and 22 in Belgium. This led to the Dutch Government introducing the Delta Plan (full closure of three northern inlets) designed to prevent a repetition of this disaster (Gerritsen, 2005). The aim was to connect the coastal high dune system in an almost continuous line, so that low-lying areas would be safe. After any major disaster
the traditional model of post-disaster financing, relying on slow and unreliable assistance from the international community, the diversion of budget allocations from development to recovery, or raising new debt in expensive post-disaster capital markets, is increasingly inefficient as disaster occurrence and the magnitude of loss increase.
(UNISDR, 2009)
The key is to undertake measures to increase resilience before any disaster strikes.
On the non-European front, Ashdown (2011) has commented that in 2006, Mozambique requested Sterling £2 million from the International Community (IC) in order to carry out engineering coastal protection countermeasures for potential flooding. This was tu...
