The management of coastal erosion

Ocean & Coastal Management xxx (2017) 1e17

Contents lists available at ScienceDirect

Ocean & Coastal Management journal homepage: www.elsevier.com/locate/ocecoaman

The management of coastal erosion Allan Williams a, b, Nelson Guillermo Rangel-Buitrago c, *, Enzo Pranzini d, Giorgio Anfuso e a Faculty of Architecture, Computing and Engineering, University of Wales: Trinity Saint David (Swansea), SA1 6ED, Mount Pleasant, Swansea, Wales, United Kingdom b CICA NOVA, Nova Universidade de Lisboa, Lisboa, Portugal c
sicas, Universidad del Atla
ntico, Km 7 Antigua vía Puerto Colombia, Barranquilla, Atla
ntico, Departamentos de Física y Biologia, Facultad de Ciencias Ba Colombia d  di Firenze, Italy Dipartimento di Scienze della Terra, Universita e
diz, Polígono río San Pedro s/n, 11510 Puerto Real, Departamento de Ciencias de la Tierra, Facultad de Ciencias del Mar y Ambientales, Universidad de Ca
diz, Spain Ca

a r t i c l e i n f o

a b s t r a c t

Article history: Received 14 December 2016 Received in revised form 22 February 2017 Accepted 19 March 2017 Available online xxx

At present, accelerated coastal erosion due to anthropogenic pressure is prevalent. Standard defence techniques to combat erosion include hard/soft protection measures (hold/advance the line), accommodation, managed retreat and sacrifice. To these conventional coastal management practices, is added a further new end point e intervention with respect to the causes, which necessitates further management action. Managed retreat and sacrifice areas are becoming increasingly popular options, which involve the input of communities and many global examples are given of comparative studies geared to combating erosion - including management theory. In particular setback lines and shoreline management plans are emphasised and coastal erosion management policy decisions for the UK are discussed in detail, as well as examples taken on a global basis. © 2017 Elsevier Ltd. All rights reserved.

Keywords: Erosion Management Sacrificial/setback zones

Contents 1. 2. 3. 4. 5. 6. 7.

8.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Causes of erosion/protection measures (hard/soft) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Managed retreat/realignment (MR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sacrificial areas (frequently referred to as ‘abandoned’ areas) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1. Management tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.1. Shoreline management plans (SMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.2. Setback zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1. Introduction

* Corresponding author. E-mail address: [email protected] (N.G. Rangel-Buitrago).

‘Strategic planning for the management of our coasts relies implicitly upon an understanding of the physical processes responsible

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for shaping coastal morphology’ (Reeve and Spivak, 2001, 55). These physical processes ultimately result in erosion and its corollary deposition, which in turn can be aggravated by anthropogenic influences. Reaction to these processes is determined by government policy/private actions and the mechanisms of implementation lie via the relevant strategy adopted einstitutional, legal, technological and financial and with regards to coastal erosion the options can be summarized in Fig. 1a. This is an axiom that is accepted without any real discussion by the scientific community and given as a ternary classification for actions to address coastal erosion, i.e. Defence, Accommodation and Retreat (DAR; Fig. 1b). This should be considered a fuzzy classification where these are just endmembers, leaving the possibility of a mixed strategy. Composite strategies, where end-members with different weightings can be adopted and represented by a ‘point position’ within the DAR triangle and all these actions form a fourth end-member in the fuzzy strategies classification e intervention as to the causes of erosion which gives rise to the pyramid presented in Fig. 1c. Each plan is represented by a point inside the pyramid: one, two, three of all the four components, which with different weightings can be applied to oppose coastal erosion/SLR. The weightings can change during the implementation phase, following results obtained through changing scenarios. But this is not enough: most present day erosion is produced by factors that can be contrasted, e.g. sediment bypassing at dams and harbours, river bed quarrying suppression, hill slope stabilization/ reduction, etc. all can cause fluctuations in river sediment input to the coast (Bird, 1996). Additionally, a global reduction in sediment flux to the sea induced by dams has occured, evaluated as some 1.4 billion tonnes/year pre human interventions (Syvitski et al., 2016). The nature of sediment supply and sediment budget as inputs to outcomes at the coast needs to be understood. Interruption of oil and gas extraction in alluvial plains and on the nearshore can decrease subsidence, which in many deltas has been the main reason of Relative Sea Level Rise. For example, the Piombino plain in Italy is subsiding 1 cm/year due to water extraction to serve industries; geological subsidence was 1 mm/yr (Bartolini et al., 1988). Intervention on the local/country causes of

beach erosion should be the first and main goal for any Coastal Zone Management action. The cause is usually from landward based issues; dams, structures, agricultural practice changes, etc. that should be managed on at least a regional basis, rather than sea level rise (SLR), which is discussed at international level. Therefore to manage the coast one has to look mainly in one direction, i.e. turn away rather as well as look at the sea. Management strategy choise must be based on the knowledge of the erosion processes (magnitudes-causes), property rights, funding/legislation and aesthetics and a helpful compendium on policy choice is given in ‘The Shoreline Management Guide’ (www.eurosion.org/shoreline). Until now, a high percentage of decision-making within coastal erosion management is strongly conditioned by economic considerations, based on a cost-benefit analysis approach (Cooper and McKenna, 2008) or an actionreaction basis (Rangel-Buitrago and Anfuso, 2015). However, there now seems to be a changing of the guard (Berry et al., 2013), with managed retreat being a favoured option, but few examples exist to counter-balance stakeholder fears (Pilkey et al., 2016). This paper emphasises this and the sacrifice option, as the other two alternatives have been discussed many times in many papers/ books. 2. The options It should be noted that coastlines can adapt to adjustments of natural/human systems made in response to actual/anticipated environmental changes, or from the effect of these changes. The management form taken has been mentioned and there exists the opportunity to exploit new beneficial opportunities that may arise (Fig. 1b), remembering that: a) Defence is costly and frequently temporary, consisting of ‘hard’ and/or ‘soft’ techniques and seaward side defences are built to either hold the existing defence line so that shoreline position remains intact, or to advance it, claiming further land (Pranzini and Williams, 2013; Pranzini et al., 2015, Table 1). If one looks at the extensive high rise buildings that

Fig. 1. a) Standard strategies available to Government w.r.t. coastal erosion. b). Defend, Adapt and Retreat strategies. c) Adaptation with a further axis.

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Table 1 Advantages and disadvantages associated with different types of coastal defence structure (modified after East Riding of Yorkshire Council); source: (modified after East Riding of Yorkshire Council; www.eastriding). Types

Pros

Cons

1. Effective in beach building. 1. GROYNES 2. Groynes intercept long-shore sand movement and 2. Provides a valuable amenity feature. 3. Construction is easy and quick from a range of 3. maintain beach levels. 4. materials.

1. Effective in preventing erosion and overtopping. SEAWALLS Vertical/near vertical stone or concrete wall. Can be 2. Can resist severe exposure and serve as a promenade. of various designs. 3. Many different types. 4. Safe for public use. 1. Good hydraulic performance and energy REVETMENTS ROCK ARMOUR dissipation especially in exposed sites. Sloping structures, either solid or open 2. Construction costs usually cheaper than solid construction. structures. 3. Little maintenance. 4. Can reduce toe scour if used with seawalls. 1. Promotes beach build up. OFFSHORE STRUCTURES 2. Beach maintenance (little required) reduces Reduce wave activity- waves break offshore. exposure of any main backstop defence. Shoreline wave energy reduction encourages sand deposition and reduces the potential for erosion. 1. Aids energy dissipation. SAND DUNES Can be artificial or natural and helps to restore post 2. Amenity/wildlife value. storm damage to beaches. NOURISHMENT Appears as a natural beach

front much of eastern Florida, e.g. Fort Lauderdale, the Costa del Sol, Spain, in all reality one cannot move these buildings, so what is the solution - more hard defences to counter act the estimated SLR? b) Accommodate change includes continued usage of land at risk without attempting to prevent land from being damaged by natural events allowing conservation/migration of ecosystems. There must be low cost or no cost in the scenarios. Examples would include: wetland restoration, modifying building codes - if possible, buildings can be elevated, changing land use, i.e. growing salt tolerant crops. It is an option more characteristic of flood prone areas and flood hazard warnings, flood proofing and agricultural threats tend to be the major issues involved. It increases the flexibility option. c) Managed retreat - structures moved inland/demolishing them/letting them degrade, with sea level rise is becoming more frequent but is in its infancy despite an increase in planning options (Niven and Bardsley, 2013). However, ‘Greater attention is now being paid to the advantages of retreating from the coast as an adaptation strategy, rather than implementing defences to resist shoreline change in situ’ (Nordstrom et al., 2015, 13). Retreat actions tend to be retroactive rather than proactive (Ledoux et al., 2005) but provides enhanced adaptability. For the period up to the 1950s on the Colombian Caribbean coast near to Galerazamba, a spit protected the coastal area and the settlement of Amanzaguapos (Anfuso et al., 2015). During the 1947e54 periods, coastal retreat was some 300 m, which caused spit erosion and narrowing. As a result, in 1954, the threatened settlement was relocated landward and northeast of the previous location and renamed “Pueblo Nuevo”. During 1964e74, the sand spit recorded further erosion and the southern part almost disappeared in 1984. As a consequence, Pueblo Nuevo was again affected by erosion problems and, in 1985, was further relocated 100 m eastward (Correa, 1990;

5. 1. 2. 3. 4. 5. 1. 2. 3. 4. 5. 1. 2. 3. 4. 5. 6. 1.

Can give local scour an increased erosion down-drift. Requires sediment supply. Controlling cross shore sand movement is less effective. Can have high maintenance costs (apart from rock), which makes them less safe for public usage. Rip current generation. Poor energy absorption/high wave reflection rates. Scour and wave reflection may destabilise beach. Often requires an additional energy absorbing apron. Usually expensive. Limited sea access (Fig. 4) Poor energy absorption and high wave reflection rates which may cause beach destabilisation. Expensive. Often needs additional inputs. Energy absorbing apron. Limited sea access Usually massive and costly. Can create navigation hazards/Public safety issues. Can produce increased erosion downdrift. Construction usually only in shallow water depths. Water quality reduction. Bathing risks. Very susceptible to erosion

1. Needs periodic maintenance, that can be costly

Anfuso et al., 2015). Implicit in the retreat philosophy is that cost effective protection is non-viable for the location in question. However, Udovyk (2003) has pointed out the advantages of a policy of enhanced resilience to the biophysical and socio-economic systems. d) Sacrifices i.e. no active intervention. ‘Let nature take its course’ is a fine sounding phrase, but one that is very emotional and frequently mentioned where compensation and expropriation possibilities arise.

3. The background Globally and also from a coastal management viewpoint, analyses of development, revenue, etc. show that:
People are congregating along coasts and their impact will continue to rise. A gross analysis of how many people are affected by erosion/SLR has been given by the World Resources Institute (2010). Within 25 km of the coastline live 1.4 billion people, (20% of the world population); 2.8 billion (i.e. 40%) within less than 100 km in a coastal strip covering 20% of the global land surface. With SLR, damage to coastal infrastructures will invariably rise (Hinkel et al., 2014).
Coasts contribute much needed revenue to the GDP of a country, e.g. Greek tourism provides 24% of its GDP (Bank of Greece (2015)) and Greece's tourism confederation (SEPE) expected 25 million tourists to visit in 2016. Ariza (2008) pointed out that Spanish beaches contribute only 0.001% of the land surface yet produce 10% of its GDP. In a country, such as, Colombia, the Gross National Product, relating to tourism (>US$ 3,600 million in the balance of payments for travel/transportation), is the third highest source of foreign exchange after oil and coal (ANATO, 2015; Williams et al., 2016).
Sea levels are rising although no agreement exists as to the amount, simply a range has been given, but a consensus opinion

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is that it possibly could be up to 98 cm at the end of this century (IPCC, 2014). This would be disastrous on low elevation barrier islands or oceanic atolls. In the extreme case, apart from a sacrifice situation many alternatives would no longer be feasible.
There appears to be an increasing tendency for more frequent and severe storm activity but there is some debate about increased frequency (Philips and Crisp, 2012) and some areas will be more susceptible than others (Komar and Allan, 2008; Bengtsson et al., 2009; Rangel-Buitrago and Anfuso, 2013; Church et al., 2013). Berlin et al. (2013) working on modelled data suggested that there has been an increasing trend in Hs of up to 0.02 m yr1 for Atlantic Europe. In the Pacific, Barnard et al.  o and La Nin a (2015) projected an increased frequency of El Nin events would cause extensive flooding/coastal erosion independently of any SLR.
Evaluation of strategic options based on quality data, which is reliable, sufficient, impartial, consistent, comprehensive and of predictive value and organised into a logical format, should be mandatory (Williams and Alvarez, 2003).
Management efforts must adhere to risk aversion and the precautionary principle under conditions of uncertainty (Holt and Laury, 2002). As an example, in the UK tremendous storms lashed the coastline in 2007 and a succession of 12 Atlantic winter storms from December 2013 to February 2014 caused huge coastal erosion/ flooding, damage being costed as £1300 million (E.A, 2016). Lessons arising from the coastal erosion and subsequent flooding of 2007 were analysed, but were government measures implemented to alleviate the similar scenarios seen in 2014? The 12 major winter storms resulted in Cornwall needing infrastructure repairs of £4.4 million as an interim payment and a £17 million payment of

permanent capital; Perranporth alone lost some 200 m3 m1 of sand (Masselink et al., 2016). In the UK, Shoreline Management Plans (SMPs) have been introduced. These represent high level strategies, non-statutory policy documents that provide large-scale assessment of the risks associated with coastal processes and the consequences of climate change (DEFRA, 2016a). Their contents influence operating authorities and private landowners on any Local Development Plans. They are a vital tool for management without which there could be 5,000 (over 20 years) and 28,000 (over 50 years) of lost properties (E.A, 2016). A recent (November 2016) UK House of Commons Environment and Rural Affairs Committee damming report stated that major reform of the system for managing flood risk is needed as some five million people in England are at risk of flooding (www. publications.parliament; UK HoC, 2016). In the light of climate change and the increased risk of torrential rain - Winter 2015 to 2016 broke rainfall records, Storm Desmond alone costing the UK more than £5 billion - the report argued that the current organisational framework for dealing with floods was unfit. After some 20 years of adaptation and mitigation of the effects of climate change, the current Environment Agency may no longer be suitable for its purpose, e.g. it needs better partnerships with local stakeholders and the present system appears to be skewed towards dealing with the consequence of floods rather than stopping them happening. There should be a national floods commissioner, reporting to the Cabinet Office and delivery would be by new flooding and coastal boards together with a river and coastal authority. Floodwater would be stored on agricultural land and tougher rules on house building would be enforced. It suggested a post-Bexit system of farm payments that subsidises land use as a weapon via downstream flooding. The government response was

Fig. 2. The ‘blackboard’ anthropogenic causes of coastal erosion.

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that there was no need for any organisational change. It must be noted that issues with governance framework are inevitably complex, even for one area let alone a country, as resources are usually insufficient, especially with a government fixated on cost cutting.

4. Causes of erosion/protection measures (hard/soft) Some erosion causes and protection measures are summarized in Figs. 2 and 3 and Table 1. Seawalls, revetments, groynes of various types, breakwaters, beach de-watering, nourishment, dune building etc. are all standard engineering techniques to be found in many books and therefore have not been dealt with in this paper, but an exhaustive account of these structures can be found in Pranzini and Williams (2013). Additionally, there are many papers presented in this Special Issue that give succinct accounts of the varied causes of erosion of which the ‘blackboard’ shown in Fig. 2 summarises some of the main anthropogenic ones that cause diminution of sediment supplies. But a question that can be posed is, ‘can one eliminate the causes of erosion’ as, one cannot eliminate sea level rise, which is a major cause? If a harbour creates downdrift erosion (Port Talbot, UK

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harbour built to bring in iron ore for the largest British steelworks, caused extensive erosion of the adjacent Kenfig dunes), one possibility is demolition of the harbour, or a by-pass without the need to defend or retreat! This is unlikely due to economics. Likewise reduced sediment input in a river due to damming causes beaches to erode, so does one destroy the dam? The demand for workers in the coastal tourist trade in some Italian islands, has led to a return of formerly arable land to its natural cover, subsequently causing a reduced sediment input into rivers e should this trend be stopped? (Pranzini and Williams, 2013). Two examples not given in Table 1 of wrong management options utilising hard engineering techniques to combat erosion are those of cliff blasting (Fig. 5a) and water jetting in South Wales, UK (Fig. 6; Williams et al., 2002). The former was initiated in the ‘70s to try to counter rockfalls at Llantwit Major, a popular recreational bathing beach. Translation, toppling and joint block detachment are the main failure mechanisms and basal notching is very common. A rockfall from the vertical cliffs caused a death and several injuries, so a decision was made to remove the upper cliff overhangs of these Jurassic Lower Lias limestone/shale rocks. This was

Fig. 3. Some commonly used protection measures. a). Nourishment, Italy. b). Gamma groyne, Montpellier, France. c). Revetment, El Manou, Spain. d). Seawall, Towyn, UK. e). Gudong, Yellow river delta, China. Built in 1985 and named the ‘Coastal Great wall.’ It is considered to be the longest continuous defence in the world - total length of 117.28 km.

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Fig. 4. Limitations to sea access (Goa, India). Small fishing boat left at the revetment base in Goa, India; a fisherman at revetment top. The boat is exposed to wave action because it cannot be shoaled.

carried out by blasting with low density Quarrex and gelignite via 85 drilled holes into the 30 m cliff face over a 250 m beach length to produce a 25,000 m3 talus cone (Fig. 5b), deemed to protect the cliff base and producing a ‘permanent’ solution to rockfalls. Rock mass strength varied from 78 to 85 for limestones and 48e54 for shales and overall rock mass strength when calculated from the BartonChouby equation ranged from 123 MNm2 for intact limestone to 1.36 MNm2 for the jointed weathered equivalent. The high density of joint spacing gave the area a very low Factor of Safety, which reduced as the ratio of undercutting depth to tension fracture depth from the cliff face increased. When the potential thrust force value (<2.7mnM2) is low, common along this coastal stretch, cliff failure potential is high. The strength of the littoral drift was underestimated and the talus cone was removed within 5 years leaving only a thin veneer (Fig. 5c). A pilot project at Southerndown again demonstrated a lack of understanding of the strength properties of rock materials comprising the Lias. The aim was to remove loose blocks from the cliff face that could cause serious injury to sun bathers at the cliff foot. The water jet power was sufficient to remove the interbedded weaker shale/mudstone rocks plus vegetation but had no effect on the massive limestones. The pilot scheme lasted a week and had the effect of tripling the natural (~10 cm per year) erosion rate of the adjacent cliffs. (Fig. 6). Bush et al. (1999) have given a succinct summary of an inventory regarding risk and mitigation for coastal areas (Table 2) and it is interesting that managed re-alignment/sacrificial zones are barely mentioned; as also is dune breaching, such is the speed of current coastal erosion mitigation thinking. If stabilization benefits exceed cost then the retreat option should be re-evaluated, but economics is invariably the final arbiter. 5. Managed retreat/realignment (MR) Managed Realignment can reduce the effect of both coastal flooding and erosion on coastal anthropogenic structures. It is a very broad term and relates to land use change and relocation of existing infrastructure. It is the deliberate process of altering flood defences to allow flooding of a presently defended area. Managing

this process helps to avoid uncertain outcomes and negative impacts and also helps maximise potential benefits (Leggett et al., 2004).Some terms may be used as an alternative to managed realignment. These include managed retreat, dike realignment, dike (re)opening, de-embankment and de-polderisation. MR allows the shoreline (which could be armoured/diked/natural) to move, but the process is directed by management, e.g. by shortening/lowering coastal defences; breaching dunes to allow sand to move freely into the system. For example, at Kenfig dunes, Wales, UK (Fig. 7) three phases of trial dune rejuvenation works covering 10.6 ha at a cost of £132,000 were carried out from 2012 to 2014. Bare sand covered some 154 ha (17.4% of the site) in 1941, but this figure had declined to only 4 ha in 2009 (0.5% of the total area) that had a significant negative impact on the conservation status of this location (Howe et al., 2012). Man sands, UK, one of the original case studies in the National Trust (N.T, 2005) report, has recently instigated removal of degrading coastal defences allowing farm land find its level, as well as, managing public access (coast path) and public perception for the idea. The technique is usually less costly than structural stabilization projects, which are invariably a temporary solution, especially in highly erosion prone areas (Zhu, 2010), It assumes that over time shorelines have been dramatically interfered with and changed both by natural and anthropogenic means, usually focuses on removal or landward relocation of coastal defences returning infilled land to the sea, allowing for the resumption of beach erosion and sedimentation processes, and growth of intertidal mudflats and coastal vegetation. In essence it allows an area that has not been previously exposed to the sea to become flooded and frequently involves the removal/ breaching of any existing coastal protection. It constitutes a dynamic change to the existing environment by creating space and enhancing the natural adaptive capacity of inter-tidal habitats, which could involve removal of people, houses, etc. in the infrastructure of a high risk area and is a long term strategy (Morris, 2012). For example, the tectonic setting along the Pacific coast of Colombia has given rise to several geological hazards, such as, earthquakes, tsunamis, subsidence, flooding and soil liquefaction.

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Fig. 5. a) Initial rock fall that caused a death and trial blast; b) resulting talus cone; c) current view. d) typical rockfall.

El Choncho village located on the San Juan River Delta started to record erosion problems in the early 1970s and erosion rates accelerated after the occurrence of the November 1991, magnitude 6, earthquake, which produced sand liquefaction, water-soil expulsion and land cracking. Erosion rates increased to 11 m/year from 1993 to 1997 and in 1998 the whole village was moved 200 m landward to a safe location (Correa and Gonzalez, 2000). This raises an interesting discussion point, i.e. can evacuation always be considered as a MR strategy? In the above case there was no planned or management strategy involved, the village usually was moved when in danger. In the Pacific region of Colombia, adaptation as a result of a meso-tidal regime is a normal response to danger situations. For locals, Governmental relocation practices are considered unnecessary and in some cases are very unpopular because villagers can lose all their belongings (as an aside, much money destined for this strategy, tends to be ‘lost’). Here, institutional distrust sometimes slows down coastal erosion management practices and this was the reason government chose to build groins and breakwaters at a cost of US$ 3 million at Tierrabomba island fronting Cartagena (Rangel-Buitrago et al., 2015). Here, locals were given the choice of relocation or protection and the later was chosen due to institutional distrust, despite the villagers living in conditions of abject poverty. This highlights cultural and institutional differences between countries. MR could be very specific, e.g. relocation of the iconic Cape Hatteras lighthouse in the USA, as the lighthouse stood some 50 m from the sea and in 1999 was moved 880 m inland over 23 days at a cost of $9.8 million. The main MR disadvantages are loss of private properties and commercial income plus the social cost might be unacceptable to stakeholders (Niven and Bardsley, 2013). It is not politically and economically viable for urban areas or where

agricultural land is of high quality becoming a coastal management utopia. It is appropriate in areas where low cost agricultural land holds sway, where there are few structures, or directly affected stakeholders and costs of compensating owners are minimized i.e. there is no high opportunity cost (Rupp-Armstrong and Nicholls, 2007). The costs of managed realignment schemes can vary widely as a result of these factors (Zhu, 2010):
The land cost where managed realignment will be performed.
Requirement for compensation to land owners/occupiers.
The need to dismantle human-made structures present on the site to prevent marine pollution.
Requirement for and size of sea defences to protect the hinterland.
Availability and cost of human resources including expertise.
Scale and frequency of monitoring. These non-structural solutions are usually more cost effective than armouring and, ‘a long term policy of MR can limit a communities exposure to coastal hazards, save lives, and limit the expenditure of public funding on vulnerable infrastructure and response mechanisms’ (Siders, 2013, 2). MR builds resilience, reduces the impact of coastal hazards on infrastructure, and limits coastal development in certain locations. However, stakeholder resistance can be large, even on low-energy coasts, as cost and benefits information, and examples about managed retreat are frequently lacking; all are large factors in stakeholder acceptance (Myatt et al., 2003; Lorenzoni and Hulme, 2009). MR involves well thought out plans for abandonment of communities and/or ecosystems with a landward shift of the

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Fig. 6. a) Water jetting at Southerndown (Wales); b) The end result. Table 2 Geo-indicators needed for coastal-hazard risk and mitigation (after Bush et al., 1999). Abandonment Relocation Active (relocate before damaged.) Passive (rebuild destroyed structures elsewhere). Long-term relocation plans for Communities. Soft stabilization Adding sand to beach via Beach replenishment. Increasing sand dune volume. a) Sand fencing. b) Raise frontal dune elevation. c) Plug dune gaps. Vegetation Stabilize dunes (oceanside). Marsh (soundside). Hard stabilization Shore parallel. a) Seawalls. b) Bulkheads. c) Revetments. d) Artificial islands/shoals. e) Offshore breakwaters. Shore perpendicular. a) Groynes. b) Jetties

Modification of development and Infrastructure Retrofit homes. Elevate homes. Curve and elevate roads. Block roads terminating in dune gaps. Move utility and service lines into the interior or bury below erosion level Zoning, land use planning Recognize hazard areas and avoid. a) Tidal inlets (past, present and future). b) Swashes. c) Permanent overwash passes. Setbacks. Choose elevated building sites. Lower-density development. Things to keep in mind Each island or coastal community is different Consider the entire coastal zone not simply the oceanfront Rising sea level must be considered.

Fig. 7. Kenfig dunes, Wales, UK. a). breach through foredunes to beach; b). view inland from the breach; c). backdune area with new sand.

ecosystems. Risks generally motivate this option due to continued occupancy and use, costs of preventative measures and asset productivity. Measures that can be undertaken include enforcing coastal no build areas, restricting coastal improvements of existing structures e.g. seawalls. Using an ecosystem services approach involves explicit assessment of Eco services, marginal changes,

possible double counting, non-linearities and threshold effects. Turner et al. (2007) and Luisetti et al. (2011) assessed the criteria necessary for economic evaluation of coastal realignment schemes in the Humber estuary, UK, concluding that the Net Present Value of MR schemes would be positive after a time period of 50e100 years in contrast to a negative value for the business as usual scenario.

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In the UK, MR is geared mainly for natural habitat types, which are frequently small and isolated and Lawton et al. (2010) proposed 24 recommendations for dealing with habitat restoration and recreation strategies. The policy for managing these areas (minimum standards and environmental acceptability), is set by the UK Department of Farming and Rural Affairs (DEFRA) whilst strategy is carried out by the Environment Agency (EA). By 2030 the UK Government hopes to create 6,200 ha of tidal wetlands at a cost of up to £15 million/year (CCC, 2013). Regional Habitat Creation Programmes (RHCP) are aimed to be proactive to landowners, but this is politically very difficult, as the perception is of ‘giving up land to the sea.’ The RHCP seeks willing landowners to develop MR projects and then the EA acquires them. A big conundrum is whether people are happy paying for projects that benefit basically wildlife and other environment values? DEFRA are piloting several schemes via the ecosystems approach e.g. Deben, Suffolk, and biodiversity offsetting is one of the ways of making more benefits through planning (Esteves, 2014), as it compensates for harm done to wildlife sites and can support MR. Results will soon be reflected in the 2016e2020 strategy papers. The key as always is to reduce the number of people and assets that are at risk in some defined area (www.gov.uk/gov/consult). East Anglia in 2004 was the first site selected for the MR programme. The costs and benefits of seawalls and intertidal habitats needs to be carefully considered when developing a strategy for MR coastal protection, but over a 25 year timespan, MR can be an economic efficient policy instead of a policy of ‘holding the line’ (TEEB, 2011). In 2002, a MR scheme was undertaken at Abbotts Hall Farm in Essex, UK. The site had a total area of 0.84 km2 and had been protected from inundation by seawalls for more than 200 years (ABPMER, 2010). MR was pursued at the site with the primary objectives of flood defence cost reduction and intertidal and coastal habitat creation. These objectives were selected because the existing seawall was in a poor state of repair and because in the UK, many, but not all since de-industrialisation, coastal habitats are in decline. Monitoring was carried out by the Environment Agency, English Nature and the Essex Wildlife Trust for three years prior to implementation, which helped ensure that the scheme design would achieve the desired results. Monitoring also provided a baseline for evaluating the effects of the project. Following realignment, a further five year monitoring programme was undertaken to assess the effects and provide information to aid the design of future schemes (Essex Wildlife Trust, 2003). For seven years before breaching, 0.2 km2 of the site had been subject to regulated tidal exchange. This helped to facilitate a significant build up in the site's surface elevation and gave a ‘head start’ to both the ground conditions at the site and to the availability of suitable plants to initiate colonisation by intertidal species (Nottage and Robertson, 2005). The final cost of the project was US$7.7 million (at 2009 prices) and was funded by the World Wildlife Fund (WWF) and the English Heritage Lottery Fund. The scheme has been considered a success as the objectives of flood defence, cost reduction and coastal habitat creation were all realised and confirmed by monitoring results. Currently the UK is part of the European Union, but aims to leave sometime in the future and the effect of current European legislation affecting future Managed Retreat is not known. However at the moment two main European frameworks have to be adhered to:
EU HABITATS & BIRDS DIRECTORY, which states that there must be no loss on intertidal habitats and any impacts on NATURA 2000 sites MUST involve a compensation measure. For example, Farlington, UK, marshes can create an intertidal area to compensate for 100 years of coastal squeeze (Esteves, 2013).

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EU WATER FRAME WORK DIRECTIVE (WFD) managed and implemented by the River Basin Management Planning, looks at the potential impact of flood defences on water quality, which impinges on this paper's topic but marginally. European countries also have to obey the above directives. In France, under the guidance of the Conservatoire du Littoral, the first MR in 1999, created a 132 ha site - the Polder de Sebastopol, Vendee - as an intertidal habitat for birds protected by a seawall. It is now part of the Pays de Loire Regional Natural Reserves, compulsory purchase post storms being the primary method undertaken. In Belgium, the main MR relates to the Sigma plan, mainly for flood management and improving the Schlecht watershed areas. It contains 1,300 ha of flood storage and 850 ha of new habitats. Several new projects with a five year time span have been introduced into selected areas and expropriation and purchasing of freeholds are carried out. In the Netherlands, a policy was set in place in 1990 to keep the coastline inviolate (hold the line) and a ‘building with nature programme’ inaugurated involving a variety of ecosystem measures as a result of intertidal habitat loss to harbour development etc. The Rijkswaterstaat is the responsible agency but MR has been strongly opposed by the public, as the country has a long history of dike construction allied to land reclamation. No coastal areas are being sacrificed, there are a few studies, e.g. Hedwigepolder in Zeeland but this is meant as nature compensation for deepening the western Scheldt, but nothing has been politically decided. In Germany the northern coast has 29 MR, the bulk being compensation for habitat loss and the Kreets project, Hamburg, involves breaching of the Elbe defences (Pranzini and Williams, 2013). 6. Sacrificial areas (frequently referred to as ‘abandoned’ areas) Sacrificial areas is the other main option available for coastal management and any strategy for letting shorelines retreat naturally needs to:
Identify the rationale behind the decision.
Use demonstration sites to present the feasibility of accommodating retreat.
Assess the geomorphological/ecological changes and indicate the advantages of allowing them to occur. It is a frequently used strategy post violent storms/hurricanes which leave houses battered and broken. Buildings have fixed life spans and when this occurs they are allowed to decay, especially if erosion is rampant in the area. Twenty nine villages have been lost along the Yorkshire coast of UK during the 20th century; in the USA, barrier island communities have suffered a similar fate, e.g. Broadwater, Hog Island, VA in 1933 (Neal et al., 2005). In 2002, 151 coastal sites in England and Wales were listed by DEFRA and EA (2002), where defence line retreat has been adopted as a strategy for coastal protection. From this 41% were classified as actual managed realignment sites and 59% as limited intervention sites since defence line retreatment was not actively managed. Since then, several locations have had failing coastal defences removed and natural processes allowed to rule, e.g. Brownsea Island, Poole, UK, where thousands of wooden pilings and gabions were removed between 2011 and 2013. Barrow hill, Mersea Island, UK is another good example of a ’do nothing’ unplanned sacrifice on a small site. It had earthbound enclosures up until 1840, which had been repaired many times; post this date stone walls were utilised, which again necessitated many repairs and it now is an excellent wildlife habitat area (E.N, 1996).

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Table 3 Some areas at risk in Wales, UK (adapted from www:bbc.co.uk; authors emphasis in italics). Newton, Porthcawl Although defences would be maintained for as long as possible, they will be allowed to fail. This would result in increased flood and erosion risk and potential loss of frontal properties. Swanbridge, Sully Existing defences will be maintained in the short term then allowed to fail. This is likely to result in the loss of residential and non-residential properties along the coast. Oxwich Bay, Gower Properties adjacent to the shore are at risk from coastal erosion and flooding. It is unlikely that new defences would be constructed and therefore there will be an increased risk of coastal erosion and flooding. Port Eynon Bay, Gower Properties adjacent to the shore are at risk from coastal erosion and flooding. It is unlikely that new defences would be constructed and therefore there will be an increased risk of coastal erosion and flooding to these properties. Amroth Once the existing defences fail the shoreline will be allowed to naturally evolve and retreat which will result in the loss of frontal properties. Wiseman's Bridge Properties are likely to be lost due to coastal erosion at Wiseman's Bridge where defences will be maintained in the short term, before being allowed to fail in the medium and long term. Angle It is unlikely that existing defences will be maintained or upgraded. Adaptation measures may include relocation of assets. Poppit Dunes, near Cardigan There would be no guarantee that defences to properties within the dunes would be protected and further defence may not be permitted. Fairbourne embankment (Fig. 7) Would involve the relocation of property owners and businesses from Fairbourne. Pontllyfni, Caernarfon At Pontllyfni, there would be no intent to protect against further erosion and there would be loss of properties at the sea front. Hirael, Bangor It is not considered sustainable to maintain the shoreline defence over the period of the SMP. To take this approach would require developing a plan for moving people and businesses from the area.

In UK, Non-governmental organisations, e.g. the National Trust (NT), has as one of its main principles that it will only support interference with natural coastal processes where it believes there is an overriding benefit to society in social, economic and environmental terms. At Porlock, Somerset, the Trust refused to strengthen a gravel ridge and it breached in a 1996 storm (Watson, 2006), i.e. work with natural processes and take a long-term viewpoint. In the South Downs, UK, the National Trust (N.T, 2005; 2015) has explicitly stated that there will be no human interference with natural geomorphological processes, e.g. shingle, rocky shore, saltmarsh, etc. The main thrust has come from the UK Government with the production in England and Wales (by Natural Resources Wales) of a second generation of Shoreline Management Plans (SMP, 2009) drawn by coastal groups, local authorities, community groups. These look at defence strategies in view of the expectation of sea level rise e it is widely accepted that climate change producing more aggressive marine conditions will lead to an acceleration of coastal erosion - and the coast was divided into several distinct ‘policy zones’ (DEFRA, 2016b). At each zone, defence mechanisms (groynes, revetments etc.) were looked at and a decision made as to

whether to continue with the defences, if they should be changed, or left alone. In Wales, a total of 48 areas were deemed at risk and some of these plus comments are shown in Table 3. Newton revetment in Porthcawl (Fig. 8 a and b; Table 3) was repaired in 2016 at a cost of £325,085.74 and it is unlikely to have further work carried out post 2032, so some residents have already installed flood gates (Fig. 8c). Fairbourne's seawall (Fig. 9 a, b; Table 3) is expected to be defended from flooding for the next 40 years (from a base line of 2014) with the uncertainty range set between 2042 and 2072. A new £6.8million scheme completed in 2015, involved strengthening 1.8 miles of the tidal defences at Fairbourne and Arthog, which will protect over 400 properties in Fairbourne from potential tidal flooding from the Mawddach estuary (NRW, 2016). It also shields Fairbourne from fluvial flooding by rebuilding the Henddol and Morfa river outfalls to better control flood water. Evacuation of residents will only be considered if the flooding risk is deemed unacceptable or a catastrophic storm event occurs and timescales will be reviewed in the light of SLR, ground water changes etc. It should be noted that sometimes policy changes can occur, i.e. from ‘Hold the Line’ to ‘No Active Intervention’ after the first 20

Fig. 8. a) Newton revetment, Wales, UK. Breaching will flood the low lying car park and housing area. b) View towards the revetment from the car park, c) Flood gates installed at several houses.

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Fig. 9. a) Fairbourne seawall, Wales, UK. b) The ‘do nothing‘ approach to the seawall will sacrifice the low lying town, The flood plain can be seen beyond the houses whose foundations are below the high tide level. Pebble movement is northwards seen by the deposition around the concrete pillars.


Raising qualification levels to those available in countries, such as, Australia and New Zealand. This will make qualified I-Kiribati more attractive as migrants and also improve local standards of service.

7. Management

Fig. 10. Deliberate and emergent strategies (modified from Mintzburg, 1994).

years of the SMP's plan, and vociferous stakeholder activity is being currently carried out against decisions given for the above two examples. Funding is a key question and conditions might be set, e.g. ’hold the line’ only benefactors pay the cost, otherwise the area could be sacrificed. An assumption is made that funding for SMPs is maintained into the future, as without this, the number of UK properties lost in the next 100 years could increase to over 74,000. A good example of sacrificial area is the "migration with dignity" strategy proposed by the Kiribati Government, which it is hoped will become common practice to be used by others in the future (O'Brien, 2013). The Government of this string of 33 narrow coral atolls dotted around the international dateline in the Pacific Ocean, purchased land in 2014 in Fiji (3458 km away). Kiribati has more than 100,000 citizens and its main island, Tarawa, suffers from severe overcrowding. The islands experience extensive coastal erosion that is now displacing people from traditional houses that have been occupied since the early 1900s. Currently, the sacrificial areal strategy of the Kiribati people involves two key components:
Enable migration of those who wish to do so now and in the coming years. In theory, this will assist in establishing expatriate communities of I-Kiribati, who in the longer term will be able to absorb and support greater numbers of migrants. It will also benefit those who remain by lifting remittances levels.

Management norms relate to analysis, planning, implementation and control and Fig. 10 is the classic Mintzberg (1994) diagram of any realised final strategy, this is a combination of intended and/ or emergent events not involved with the intended strategy, as they represent responses to intended strategy, so managers must be adaptive and able to learn/re-adjust from experience of an event so that policy is kept in line with environmental change, as 'logical incrementalism.' Crisis management is invariably high risk and costly, so it is very advantageous to manage pre any crisis event. But do governments ever learn this dictum? Any strategic management involves a process of making and implementing strategic decisions and involves: Analysis, where managers seek to understand the context of the system/organisation and existing management decision, resulting in a choice between possible courses of action; making a Decision to react or do nothing; followed by Implementation, whereby the chosen option is put into effect (Fig. 11). Making strategic decisions usually involves considerable uncertainty, ambiguity and in the case of erosion management strategies, a high monetary cost. Pre any strategic decision made there must be a formalised, structured and systematic data collection, i.e. ‘get’, ‘order’ and ‘refine’ information. Unfortunately the environment is not always viewed objectively as other factors come into play, e.g. ideas, devolution, legality, media, public opinion, Parliament, crises, Party manifestoes, personal ambition, lobbying, costs, global pressures, dogma, etc. Any Government decision making and planning models should always be rational with planning models constructed around:





Obtaining evidence obtained from environmental monitoring. Setting of clear objectives e focused intentions. Further monitoring past decision making. Evaluation of strategic options.

There appears to be several problems in implementing a long term strategy and a major one is that the political life of politicians is usually much shorter than the time taken to produce results;

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Fig. 11. The coastal management cycle (modified from Moser and Echstrom, 2010).

election time almost demands results and seawalls, groins etc. are considerably more visible than any lines on maps and restrictions. Additionally, the changing role and findings of science play a large role. Rationality involves diversity, problems of information quality and managerial psychological make up, and all can lead to nonrational decisions. Rational techniques can assist choices, but not make those choices due to qualitative environmental variables. Also, making analysis too rational is questionable since the

approach could become inflexible, formalised and excessively quantitative. As Lenz and Lyles (1989) noted, any management policy made entirely on the basis of hard facts, could lead to 'paralysis by analysis.' Rational analysis through environmental monitoring is the mantra and this should force decision makers to confront the needed value judgements that have to be made, but in practise, conflict tends to occur within Government level politics, frequently due to:

Table 4 Some main tools available to Government. Coastal planning: 1. At all levels and establishment of clear objectives and goals. 2. Co-ordinated efforts appertaining to consistent and complimentary goals. Setback lines: 1. Set distances plus erosion rates will enable a figure to be given, e.g. 20 m in New Zealand. 2. Act now. Any structure seaward of the line is at the owner's risk and money. For example, the Government initiative Coastal Erosion and Planning Act provides $50,000 for Texas property owners to realign houses from public beach areas to inland ones (Tam, 2009). The Rivers and Harbours Act, 1899, ensured free navigability to the nation's waterways. Due to sea level rise, four structures originally inland of the high water mark were found to trespass this mark in violation of section10 of the Act and the houses had to be removed. 3. Question hard engineering solutions unless absolutely necessary, e.g. the defence of big coastal towns, e.g. Towyn, Wales (Fig. 2d), where a £11 million seawall has been recently built (Pranzini and Williams, 2013). 4. Provide enforcement mechanisms to ensure the above are carried out. 5. Have explicit legislation as it can play a large part. For example, the Coastal Barrier Resources Act, USA, 1982, designated undeveloped coastal barriers ineligible for federal funding, so anyone building a property there post this date had to bear any economic cost and between 1982 and 2000 $1.3 billion of taxpayer's money was saved (CCC, 2013). 6. Assess and explain risk to the public, e.g. by public forums. (Rangel-Buitrango and Anfuso, 2015). Armouring: 1. Legislation and regulations should be carried out quickly. 2. Make the burden of proof on the landowner. 3. Have a coherent CZM/Marine Spatial Plan (MSP) in place. Many countries now have these on statute books but implementation varies. Acquisition: 1. Relocate is the key.so provide incentives and identify safe areas. But coastal protection is geared to set magnitude events e the UK 2013/14 winter storms exceeded these, as did, Sandy in New York; Xinthia in France, 2012 and Katrina in New Orleans. 2. Encourage owners to stay and rebuild close to their community. This is easier stated than done in practice. 3. Keep programme cost effective by having a cap on the offered amount (Tam, 2009). Rebuilding Restrictions: 1. Implement these together with zoning as quickly as possible. 2. Prohibit repetitive repairs. New Jersey, USA, prohibited rebuilding on the most vulnerable coastal areas post Hurricane Sindy. 3. Educate the public regarding risks. 4. Place the burden of proof on the home owner. 5. Have in place a coherent CZM strategy/MSP (EC, 2014).

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A general ignorance or denial of processes.
A clinging to the Newtonian solution of: right vs. wrong; win vs. lose, rather than a win-win solution.
A heavy reliance on marginal society segments, which have overt influences.
A differential perception of environmental threats, i.e. local groups vs. general strategic interests. The everyday business of Government is where, ‘policy is actually made, choosing among alternatives is always the order of the day,’ (Field and Field, 2002, 19). Major differences can, ‘produce irreconcilable differences in management objectives, both between stakeholders and between them and management authorities’ (McKenna et al., 2008, 953). There also appears to be a decay of self-policing by learned professions and many resort to litigious procedures, particularly at the local level (Komar, 2009). However, the goal should be long term strategies and one of the harsh facts of government life is, as stated above, that a politician's political life is shorter than the time frame needed to show results. International events involving huge tourist numbers have proved to provide the impetus for improving tourist infrastructures. For example, the Olympic Games in Barcelona, Spain was the occasion for several

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beach nourishment projects in Catalonia and Murcia; the Holy year (Catholic Jubilee) triggered beach nourishment at Ostia (Roma, Italy), all geared to extend tourist attendances not only for the occasion but the future. Small changes in any policy frequently do not occur at the same time as environmental change and vice versa; 'strategic drift' occurs and fundamental policy realignment becomes necessary, as most strategies undertaken at government level are sectoral. But whatever, strategy is chosen, it is but one of myriads of options that Government has to make bearing in mind a host of competing factors that all claim precedence. On a national scale, accurate economic assessments of resource allocations should be determined sensibly by relating both to the scale of the risk and provide a benchmark re a possible future.

7.1. Management tools A variety of tools can be used by Government to help cut down coastal erosion. As well as the standard engineering practises mentioned earlier, these include science (data collection, baseline studies), policy (green and white papers, tax incentives), legislation (Acts, regulations, CZM, SMPs Climate Adaptation and Hazard map

Fig. 12. SMP proposed for MR in the UK (Committee on Climate Change, 2016).

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plans, zoning, setbacks), support (EIA, capital inputs, stakeholder awareness standard setting) and monitoring/reviews/assessments (Grannis, 2013; CCC, 2013). Table 4 sums up the main points and two examples are given: Setback zones and Shoreline Management Plans.

7.1.1. Shoreline management plans (SMP) SMPs based upon the sediment cell principle, are a major universal ICM tool and are very applicable to the broad-brush integrated management approach for coastal zones, but frequently they do not always agree with the jurisdiction of local authorities. In the UK, DEFRA and Welsh Office (MAFF/Welsh Office, 1993) publications were the initiating agencies for SMPs, which are high level, non-statutory documents representing large-scale risk assessments associated with coastal evolution in both cultural and natural environments. They are planning process guidance documents that identify constraints to coastal dynamics and identify potential risk areas together with the consequences associated with decisions producing differing future scenarios, especially in the realm of coastal engineering. Proposed MR areas for the UK are shown in Fig. 12. Most UK first-generation SMPs had five-year revision cycles. In 2000, the UK's Ministry of Agriculture, Food and Fisheries (MAFF, 2000) recommended future SMPs would:
Have a policy consideration of 100 rather than 50 years.
Involve stakeholders. The Environment Agency has strategic oversight of all SMPs and quality control on behalf of DEFRA (DEFRA, 2005). These recommendations were further refined in 2003 and finally implemented in 2006 (DEFRA, 2006) These second-generation plans considered longer-term implications, i.e. 50e100 years in view of climate change and have a more involved and focused consultation with stakeholders. It put forward the view that policy decisions are initially based upon appraisal of achievement of objectives and not on any economic appraisals. Twenty two SMPs cover the England coastline envisaging three scenarios of 0e20 30e50 and 50e100 years. Stretches of coast are divided into ‘management units’, which tend to be universally agreed upon, and the strategies given in the Introduction section of this paper for these units are:
Seaward side defences are built to either hold the existing defence line, by building or maintaining artificial defences so that shoreline position remains intact, or to advance it, in which case the policy should be limited to units where significant land reclamation is considered. At Sea Palling, UK, 50,000 tonnes of rock armour (rip rap) in 1995 were placed at the sea wall foot to

Fig. 13. Example of Setback lines.

prevent further undermining, artificial offshore barriers together with 1.4 million m3 of sand. In addition, four 250 m offshore bars were constructed (240 m long with a 250 m gap) costing £5.9 m, which used 312,000 tonnes of rock. They were 2.8 m above sea level and soon tombolos formed, which interrupted longshore drift causing downdrift erosion. A further five reefs were constructed in 1996, 1.2 m above sea level to counteract this deposition, using 20,000 tonnes at a cost of £10.5 m (www. northeNorfolk). Since 2010, a £11 million concrete stepped seawall and new timber groins have been inserted into the beach of a resort town, Towyn, UK (Fig. 3d), to ‘hold the line’ (Pranzini and Williams, 2013). The Crown Estates are investigating a ‘Sandscape’ project based on the Dutch Sand Engine principle (where 21 million m3 of sand deposited on the Netherlands coast is allowed to redistribute naturally) at several locations, e.g. north Norfolk, Suffolk, Lincolnshire, north-east Wales, as well as other pockets in NW England and the south coast (Tudor, pers. Comm.). However, these are early days as problems exist, i.e. finance, there exists a fear of being the ‘first of its kind’, licencing, etc. A technical first cut by consultants has been made but no detailed modelling has been carried out and in most cases uncertainty remains. Elsewhere, examples are ~ as, Colombia; Scheveningen, Netherlands. In Tolu and Coven 1990, the Dutch government brought out a new policy called ‘dynamic preservation’ where the coastline was to be kept in the 1990 position and where necessary, since 1996, soft measures (nourishment) have been utilised to counteract erosion (van der Meulen et al., 2013). In this context, a point to consider is that with rising sea levels, beach nourishment will have a shorter life-time span, necessitating increased costs and presumably at some level will no longer be feasible.
No active intervention (Sacrifice). No planned investment in defending against flooding or erosion, irrespective if artificial defences had previously existed e.g. Fairbourne, Wales (Fig. 9a and b; Table 3).

7.1.2. Setback zones The MR approach is frequently coupled with several other planning and regulatory techniques including identification of areas of high risk; regulating structure types. For example, making structures easy to relocate; buy-back programmes/compensation, buffer zones, Environmental Impact Assessments. Set back zones are sometimes synonymous with buffer zones - leaving of undeveloped land on designated areas, or easements. They provide a highly effective method of minimising property damage due to coastal flooding and erosion by removing structures from the hazard zone. They provide a low-cost alternative to shoreline erosion or flood protection works, such as, seawalls or dikes which have their own dis-advantages. Two kinds of setbacks occur: Vertical, which establishes a height above a sea level bench mark to prevent infrastructures from inundation; Horizontal, a horizontal distance from a seaward benchmark to define an area at greatest risk of coastal hazards (Fig. 13) and they are good tools for developing a protocol. The horizontal distance varies according to country. For example, Chile 80 m, Colombia 50 m, Ecuador 8 m plus a greenbelt for mangroves, Mexico and Belize 20 m, Nicaragua 48 m, Barbados 30 m. Cuba has six classes of coastal zones and distance varies due to location e.g. 20 m inland from the natural vegetation line, or cliff edge, 300 m inland and 60 m longitudinally from river mouths (Simpson et al., 2012). Australia has no national set back policy leaving it up to individual states. An example of setback lines for a coastal strip according to Western Australia (WA) parameters is given in Fig. 14. If no data is available the distance is 150 m and the State can add a

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Fig. 14. Schematic of a coastal area with development limitations (no new constructions, public structure removal, etc.) following criteria under adoption in some Western Australian municipalities.

distance for the public foreshore. If data is available it is 100 m from the horizontal setback level. The New Zealand Resource Management Act, 1991, sets a 20 m setback (called the Queens's chain) and Regional Councils decide setback amount, e.g. in Rodney District Council it is 50 m in rural areas, 23 m in residential areas. In the USA, The Coastal Zone Management Act 1972, administered by NOAA, has as one of its goals the minimization of loss of life and property in coastal hazard areas, to be obtained by gradual retreat from these areas. It is a federal act but one that gives greater power to the individual states. For example, Florida has two legislative tools to manage coastal development. A Coastal Construction Control Line, which is not strictly a Setback line as seaward construction is not explicitly forbidden; and the Erosion Protection Setback where buildings should be setback landward of a line drawn at 30x the predicted annual erosion rate. The Mediterranean Protocol on ICZM under the Barcelona Convention, was the first effort by a Regional Seas organisation to fix a setback of 100 m measured from the highest winter waterline (this dates back to Roman times) and had very few exceptions (Barcelona Convention, 1976). The wording was explicit as it carries an obligation for signatory nations to demonstrate effective implementation. The complexity of legal and administrative systems in the original 16

now 22 counties means implementation of this shared approach is a big challenge (Sano et al., 2010). Barbados has implemented coastal setbacks as a regulatory measure for development in the coastal zone for the past 30 years. This strategy is supported by the Town and Country Planning Act, the Coastal Zone Management Act and the Integrated Coastal Management Plan. Two setback distances are used on the island. Along sandy beaches, buildings are required to be a minimum of 30 m from the Mean High Water Mark (MHWM). In the case of development on coastal cliffs, there is a minimum setback distance of 10 m from the cliff edge. In some cases, these setbacks can be increased when rare, threatened or endangered ecosystems or important historical or archaeological sites exist. The adoption of fixed setbacks has simplified the process of implementing this measure for the whole country. However, they have also been criticised because they do not consider the historical nature of specific beach erosion trends (Daniel and Abkowitz, 2005). In some cases, the setback distance has also been questioned, because properties may still be inundated during extreme wave events. The distance adopted in Barbados is much smaller than in other Caribbean islands, for example, Nevis, which requires hotel structures to be located at least 91 m from the high tide mark (Mycoo,

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2006). In Jamaica, where a 30 m setback was also implemented, flood hazard mapping studies highlighted the fact that this distance was insufficient for provision of flood protection (Zhu, 2010). Setbacks are particularly important in Caribbean islands because of the significance of the tourism industry and the consequent need for coastal hotels and accommodation. Developers often object to setbacks because they think that insurance would not cover impending property damage (Mycoo, 2006). Also, coastal setbacks can mean that governments lose much needed tax revenues from prime beachfront properties if development is not allowed in these areas (Mycoo, 2006). For a developing country, this may be particularly troubling. When whole communities are at risk, e.g. in the 2010 storm Xynthia in France, new setback lines involved destruction of several hundred homes (Anthony and Sabatier, 2013). However, one of the main problems in defining setbacks is that, on the one hand they must be rigid entering national, regional or municipal regulations/guidelines; and on the contrary they should be flexible enough in order to fit future defined or changed scenarios. If not drafted extremely carefully, continuous revision of SLR values can make adaptation plans obsolete and trigger endless litigation. 8. Conclusions Conventional strategies for coastal management can be summed up into the end members of defence, alignment and sacrifice areas as is shown in Fig. 1a. This paper presents a triangular version with an added end point - intervention as to the causes of erosion. Different weightings which are fluid can pinpoint a position which transforms the traditional triangle into a pyramid, and these can be tracked/changed throughout the lifespan of the project. The causes of erosion have been given as a ‘blackboard’ demonstration of good and bad practices both on the coastal area and hinterland, whilst advantages and disadvantages of standard defence practices are given in order to counteract them. Managed realignment and sacrifice zones are emphasised. The former is usually less costly than structural stabilization projects and allows movement of a shoreline, which could be armoured/ diked/natural, but the whole process is management directed. Many examples from the UK are given including dune breaching to allow sand to move freely into the Kenfig dunes, Wales, system. Further examples are Cape Hatteras lighthouse in the USA, which was moved in 1999; village relocation in Colombia, and several European countries, where MR schemes have to obey the EU Habitats & Birds Directory and EU Water Framework Directive. The main disadvantages seemingly unacceptable to stakeholders are the loss of private properties and commercial income plus the social cost. Its suitability lies in areas where low cost agricultural land is plentiful rather than urban areas or where high quality agricultural land exists. The Sacrificial strategy is a frequently used post violent storms/ hurricanes which leave houses battered and broken. In the UK, the National Trust, a Non-Governmental Organisation (NGO) has a policy of ‘non-intervention’ unless it is necessary. The UK Government has produced several generations of Shoreline Management Plans geared for the next 100 years showing zonings for: no intervention, hold/advance the line, and managed retreat. Set back zones, frequently called buffer zones, can provide a highly effective method for minimising property damage due to coastal flooding and erosion and are another management option. Examples are given from the USA, Caribbean, Latin America, Australia and the Mediterranean. Governance decisions are difficult, as many contrasting disciplines all demand priority. Ageing coastal defences, communities at

risk all add to this complex mix especially for crunch locations. Knowledge regarding coastal processes abounds within the scientists/engineers cohort, but institutional reform is a challenge and governmental wisdom is questionable. Acknowledgements This work is a contribution to research groups: “Geology,
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