Chapter 9 – adapting to sea level rise

Chapter 9 – adapting to sea level rise Chapter 9 – adapting to sea level rise Chapter 9 – adapting to sea level rise Chapter 9 – adapting to sea level rise Chapter 9 – adapting to sea level rise Chapter 9 – adapting to sea level rise Chapter 9 – adapting to sea level rise

Adapting to Sea Level Rise

of land and associated assets and economic activity, the displacement of millions ofpeople, and significant coastal habitat degradation However, adaptation can greatlyreduce these impacts and promote prosperous and desirable coasts Adaptationmeasures can be characterized as (1) protect, (2) accommodate, or (3) retreat ap-proaches The provision of information measures such as warnings is improvingsignificantly, while novel methods such as ecosystem-based approaches are attractinginterest Adaptation to sea-level rise should be viewed as a process that requires anintegrated coastal management philosophy to be consistent with wider coastal ac-tivities and other stresses Hence, in addition to technical skills, adaptation requires

an appropriate institutional capacity The success or failure of measures of tion, especially protection, is contested and this influences our view of sea-level rise

adapta-as a problem Adaptation can be best analyzed in the context of understanding thecoastal system that includes the effects of all drivers, including sea-level rise, theirinteractions, and feedbacks: these types of analyses are only just beginning Someproactive adaptation plans are already being formulated, such as around London and

in the Netherlands Coastal cities will be a major focus for adaptation efforts due totheir concentrations of people and assets However, there are important challengesfor adaptation in developing countries, most especially in deltaic areas and smallislands

Coastal and Marine Hazards, Risks, and Disasters http://dx.doi.org/10.1016/B978-0-12-396483-0.00009-1

9.1 INTRODUCTION

Sea-level rise has been recognized as a global major threat to low-lying coastalareas since the 1980s (e.g., Barth and Titus, 1984; Milliman et al., 1989;Tsyban et al., 1990) There is a growing literature demonstrating that thepotential impacts of sea-level rise are large To respond to this challengeinterest in adaptation is increasing, even though it is recognized as a difficultand challenging problem (Moser et al., 2012; Wong et al., 2014) Althoughsea-level rise only directly impacts coastal areas, these are the most denselypopulated and economically active land areas on Earth More than 600 millionpeople live below 10 m elevation in the Low Elevation Coastal Zone(McGranahan et al., 2007), and the population is growing rapidly in coastalurban areas (CIESIN, 2013) Coastal areas also support important and pro-ductive ecosystems that are sensitive to sea-level rise (Crossland et al., 2005).Coasts are already “risky places” exposed to multiple meteorological andgeophysical hazards, including storms and storm-induced flooding (Kron,

2013) Threatened low-lying areas already depend on various flood riskadaptation strategies, be it natural and/or artificial flood defences and drainage

or construction methods Recent flood events such as New Orleans andenvirons on the US Gulf Coast (Hurricane Katrina, 2005), Irrawaddy delta,Myanmar (Cyclone Nagris, 2008), New York and environs (Cyclone Sandy,2012), or the Philippines (Typhoon Haiyan, 2013) demonstrate what canhappen in low-lying areas during extreme flood events Rising mean sea leveland more intense storms are expected to exacerbate these risks significantly(Wong et al., 2014)

The main focus of this chapter is adaptation, although some brief remarks

on the possible role of climate mitigation and other source control responsesare included for completeness To distinguish these responses, mitigation andadaptation are defined as follows:

l Mitigation (or source control of sea level)dreducing the magnitude ofhuman-induced climate change and sea-level rise at the global scale, orreducing the magnitude of human-induced subsidence at the locallevel; and

l Adaptation (to sea level)dreducing the impacts of sea-level rise viabehavioral changes This includes a range of changes from individualactions to collective coastal management policy, such as upgraded defencesystems, warning systems, and land management approaches

Coastal adaptation to sea-level rise has been considered for the last

25 years (Barth and Titus, 1984;IPCC CZMS, 1990), building on the sive experience in adapting to climate variability and other stresses Despitethis, the uncertainties about the success or failure of adaptation remain large,contributing significant uncertainty to the overall consequences of sea-levelrise for society (Nicholls et al., 2014a)

exten-The chapter is structured as follows First the coast is considered as asystem comprising natural and socioeconomic components, to provide anappropriate framework to analyze coasts, sea-level rise, and adaptation.Second, climate change and sea-level rise are considered in more detail,including the important distinction between global-mean and relative sea-levelrise (RSLR) Then the impacts of sea-level rise are briefly considered from aphysical and a socioeconomic perspective, including drawing on experiencefrom subsiding cities This is followed by a brief review of mitigationapproaches for sea-level rise and a more detailed consideration of adaptation.This demonstrates the complexity of adaptation and the multiple factors thatneed to be considered This is followed by a discussion/conclusion, includingresearch needs.

9.2 COASTAL SYSTEMS

Sea-level rise and the need to adapt to it does not happen in isolation: coastsare changing significantly due to more local factors such as urbanization andchanging water/sediment inputs due to river regulation and watershed land useand land cover change (Crossland et al., 2005; Valiela, 2006; Syvitski et al.,

2009) These types of problems require a systems approach to analyze the fullrange of interacting drivers, including feedbacks such as adaptation.Figure 9.1

presents a simplified systems model of the impacts of sea-level rise on thecoastal zone (Klein and Nicholls, 1999; Nicholls and Klein, 2005) This modelhighlights the varying implicit and explicit assumptions and simplificationsthat are necessary within all the available assessments of coastal impacts ingeneral, including their limitations It characterizes the overall coastal system

as interacting natural and socioeconomic systems, which have the potential toconstrain each other’s evolution Both systems can be characterized by theirexposure, sensitivity and adaptive capacity to change, both from sea-level rise,related climate change, and nonclimate stresses Collectively, sensitivity andadaptive capacity, combined with exposure, determine the vulnerability tosea-level rise and other changes

A range of drivers may influence the boundary conditions (Figure 9.1).Sea-level rise is only one aspect of climate change for coastal areas, and allclimate change drivers interact with other nonclimate stresses, often exacer-bating impacts (see Table 9.1) Lastly, the socio-economic system is notpassive as it influences the natural system through deliberate changes such asconstruction of sea dykes, destruction of wetlands, and building of port andharbor works, as well as unintended changes such as reductions of sedimentand water fluxes due to the building of dams Hence, the socioeconomicsystem is shaping the future of the coastal system as much, if not more than,the natural system and issues such as sea-level rise are shaping the socio-economic system This raises the prospect of the coast as a coevolvingsystem where the natural system shapes the socioeconomic system and vice

versa, with adaptation playing an important role in this aspect It raises a newway of thinking about the future of coasts, which requires further investigation(Lazarus et al., 2014).

9.3 GLOBAL-MEAN AND RSLR

Human-induced climate change is expected to cause a profound series ofchanges including rising sea level, rising sea-surface temperatures, andchanging storm, wave, and run-off characteristics (Wong et al., 2014) Here wewill focus on climate-induced sea-level rise, which is mainly produced by (1)thermal expansion of seawater as it warms and (2) the melting of land-basedice, comprising components from (a) small glaciers, (b) the Greenland icesheet, and (c) the West Antarctic ice sheet (Church et al., 2010; Gornitz, 2013;Pugh and Woodworth, 2014) A global rise in sea level of 17 cm was observedthrough the twentieth century (i.e., 1.7 mm/year) This observed rise is almostcertain to continue and will very likely accelerate through the twenty-firstcentury with a rise of 1 m or more being plausible if the large ice sheetsmake a large positive contribution (Church et al., 2013) From an impact andadaptation perspective, coastal policymakers are especially concerned aboutthe high end of possible changes (Nicholls et al., 2014b) While the probability

of high-end rise is unknown, the large potential impacts make them highlysignificant in terms of climate risks and policy There is also concern about

FIGURE 9.1 The coastal system comprises interacting natural and socioeconomic sub-systems which in turn are influenced by changing boundary conditions, such as sea-level rise, climate change, and large-scale nonclimatic stresses.

Interacting Factors Which Could Offset or Exacerbate These Impacts Are Also Shown Some Interacting Factors (e.g., SedimentSupply) Appear Twice as They Can Be Influenced both by Climate and Nonclimate Factors Adaptation Options are Coded:

PdProtection (Hard or Soft); AdAccommodation; RdRetreat

Natural System Effect

Possible Interacting Factors

Possible Adaptation Options

1 Inundation/flooding a Surge (flooding from

the sea)

Wave/storm climate, erosion, sediment supply

Sediment supply, flood management, erosion, land reclaim

Dikes/surge barriers/closure dams [Pdhard], nourishment, including dune construction [Pdsoft], ecosystem-based barriers (e.g., mangrove afforestation) [Pdsoft], building codes/flood-proof buildings [A], land use planning/hazard mapping [A/R], planned migration [R].

b Backwater effect (flooding from rivers)

and land use

sediment supply, migration space

Sediment supply, migration space, land reclaim (i.e., direct destruction)

Gabions/breakwaters [Pdhard], nourishment/sediment management [Pdsoft], land use planning [A/R], managed realignment/forbid hard defences [R].

wave/storm climate

Sediment supply Coastal defences/seawalls/land claim

[Pdhard], ecosystem-based barriers (e.g., mangroves) [Pdsoft], nourishment [Pdsoft], building setbacks/rolling easements [R].

TABLE 9.1 The Main Natural System Effects of Relative Sea-Level Rise and Examples of Adaptation Options Potential

Interacting Factors Which Could Offset or Exacerbate These Impacts Are Also Shown Some Interacting Factors (e.g., SedimentSupply) Appear Twice as They Can Be Influenced both by Climate and Nonclimate Factors Adaptation Options are Coded:

PdProtection (Hard or Soft); AdAccommodation; RdRetreatdcont’d

Natural System Effect

Possible Interacting Factors

Possible Adaptation Options

(over-extraction), land use

Saltwater intrusion barriers [P], desalination [A], move water abstraction upstream [R].

utilization

Insert impermeable barriers [P], freshwater injection [P], change water abstraction [A/R].

5 Impeded drainage/higher water tables Rainfall, run-off Land use, aquifer

utilization, catchment management

Drainage systems/polders [Pdhard], change land use/crop type [A], land use planning/hazard delineation [A/R].

Adapted from Nicholls (2010), see also Linham and Nicholls (2010).

higher extreme sea levels due to more intense storms superimposed on meanrise in sea level, but this is much less certain (Church et al., 2013).

When analyzing sea-level rise impacts and responses, it is fundamental thatimpacts are a product of relative (or local) sea-level rise (RSLR) rather thanglobal changes alone (Nicholls et al., 2014b) Relative sea-level changeconsiders the sum of global, regional, and local components of sea-levelchange: the underlying drivers of these components are (1) climate change,

as already discussed, and changing ocean dynamics and (2) nonclimate landlevel change (i.e., uplift/subsidence) processes such as tectonics, glacialisostatic adjustment (GIA), and natural and anthropogenic-induced subsi-dence For large ice sheet changes, gravitational effects due to mass redistri-bution of melting ice also need to be considered Hence, RSLR is only partly aresponse to climate change and varies from place to place (Figure 9.2) Wherecoasts are subsiding, such as Grand Isle in the Mississippi Delta, Louisiana,RSLR exceeds the global rise Most populated deltaic areas and alluvial plainsare threatened by enhanced subsidence (Ericson et al., 2006; Syvitski et al.,2009; Chaussard et al., 2013) Most dramatically, subsidence can be enhanced

by human activity on susceptible soils due to drainage and withdrawal ofgroundwater as shown in Bangkok (Figures 9.2 and 9.3) Dramatic RSLR hasoccurred in many coastal cities built on deltas and alluvial plains due to thiscause Over the twentieth century, the parts of Tokyo and Osaka built ondeltaic areas subsided up to 4 m and 3 m, respectively, a large part of Shanghaisubsided up to 3 m, and the center of Bangkok subsided up to 2 m Human-induced subsidence can be mitigated by stopping shallow sub-surface fluidwithdrawals and managing water levels, but natural “background” rates of

1900 1920 1940 1960 1980 2000 2020

Helsinki Sydney New York Grand Isle Bangkok Nezugaseki

FIGURE 9.2 Selected relative sea-level observations since 1900, illustrating different trends (offset for display purposes) Helsinki shows a falling trend (2.0 mm/year) as the land is rising, Sydney shows a gradual rise (0.9 mm/year), New York is subsiding slowly (3.1 mm/year), Grand Isle is on a subsiding delta (9.1 mm/year), Bangkok (Station: Fort Phrachula Chomklao) is also on

a delta and includes the additional effects of human-induced subsidence (18.9 mm/year from 1962

to 2012), and Nezugaseki shows an abrupt 150e2000 mm rise due to an earthquake Data from Holgate et al (2013); PSMSL, 2014.

subsidence that are typical of deltas (1e5 mm/year and maybe more) willcontinue and RSLR will still exceed global trends in these areas The fourcities mentioned above have all implemented mitigation policies to varyingdegrees of success, combined with the provision of improved flood defenceand pumped drainage systems to avoid submergence and/or frequent flooding.(In Bangkok, subsidence has been greatly reduced in the center of the city, but

at the site of the measurements shown inFigure 9.2, which is 20 km to thesouth, no reduction is evident.) In contrast, other cities such as Jakarta andMetro Manila continue to subside substantially, with maximum subsidence of

4 and 1 m over the last few decades, respectively (Kaneko and Toyota, 2011).Flooding and waterlogging are common and growing problems There is littlesystematic policy response to date despite these direct impacts, or the expe-rience described in other cities This suggests that the problems of enhancedsubsidence are likely to be widely repeated in susceptible coastal cities

FIGURE 9.3 Subsiding and potentially subsiding coastal cities (adapted and updated from Nicholls (2010), Hallegatte et al (2013), with additional data from Kaneko and Toyota (2011), Dang et al (2014)) The maximum observed subsidence (in meters) is shown for cities with populations exceeding 5 million people, where known Maximum subsidence is reported as data on average subsidence is not available.

through the twenty-first century It is important to emphasize that only somecities are prone to this problem: of the 136 coastal cities with a populationabove 1 million considered by Hallegatte et al (2013), only 32 have anappropriate geological setting to experience enhanced subsidence as these arecities wholly or partly built in deltaic or alluvial settings (Figure 9.3) Note theconcentration of large cities in south, South-East or East Asia.

Greater appreciation of the importance of subsidence is urgently needed

to promote responses, including planning and adaptation for RSLR In much

of the developed world quality data is limited However, new measurementsystems permit analysis and quantification, including satellite measurements(Chatterjee et al., 2006) and differential Global Positioning System (DGPS)(Teatini et al., 2005) Beyond this, the political will to tackle these issues isalso necessary as discussed byRodolfo and Siringan (2006) for Manila, thePhilippines

9.4 SEA-LEVEL RISE AND RESULTING IMPACTS

Relative sea-level rise causes more effects than simple submergence (the

“bath-tub” effect); the five main effects are summarized inTable 9.1 ing/submergence, ecosystem change, and erosion have received significantlymore attention than salinization and rising water tables Along with rising sealevels, there are changes to all processes that operate around the coast Theimmediate effect is submergence and increased flooding of coastal lands, aswell as saltwater intrusion into surface waters Longer term effects also occur

Flood-as the coFlood-ast adjusts to the new environmental conditions, including wetlandloss and change, erosion of beaches and soft cliffs, and saltwater intrusion intogroundwater These lagged changes interact with the immediate effects of sea-level rise and generally exacerbate them For instance, erosion of saltmarshes,mangroves, sand dunes, and coral reefs degrades or removes natural protectionand increases the likelihood of coastal flooding

A rise in mean sea level also raises extreme water levels Changes in stormcharacteristics could also influence extreme water levels For example, anincrease in the intensity of tropical cyclones will generally raise extreme waterlevels in the areas affected (Church et al., 2013) Extratropical storms may alsointensify in some regions, although this effect is uncertain An improvedunderstanding of these changes is an important research topic to supportimpact and adaptation assessments

Changes in natural systems resulting from sea-level rise have manyimportant direct socio-economic impacts on a range of sectors, with theseimpacts being overwhelmingly negative (Table 9.2) For instance, flooding candamage coastal infrastructure, ports and industry, the built environment, andagricultural areas In the worst case, flooding leads to significant mortality, asrecently demonstrated by Hurricane Katrina (USA) in 2005, Cyclone Nargis(Myanamar) in 2008, Storm Xynthia (France) in 2010, and Cyclone Sandy

(USA) in 2012 Erosion can lead to the loss of beachfront/cliff-top buildingsand other infrastructure, and have adverse consequences for sectors such astourism and recreation In addition to these direct impacts, there are potentialindirect impacts such as mental health problems triggered by floods, or eco-nomic effects that cascade through the whole economy These indirect impactsare poorly understood, but will have economic consequences in terms of thedamages caused (and/or the diversion of investment to fund the adaptation toavoid them) Thus, sea-level rise has the potential to trigger a cascade of directand indirect human impacts.

Importantly, sea-level rise does not occur in isolation and coasts arechanging significantly due to nonclimate-induced drivers (Crossland et al.,2005; Valiela, 2006; Wong et al., 2014) Potential interactions of such changeswith sea-level rise are indicated inTable 9.1(column entitled “Potential Inter-acting Factors”) and need to be considered when assessing sea-level rise impactsand adaptation responses For instance, a coast with a positive sediment budgetmay not erode given sea-level rise and vice versa Hence, coastal change ideallyrequires an integrated assessment approach to analyze the full range of inter-acting drivers, including the feedback of policy interventions (i.e., adaptation)

9.5 RECENT IMPACTS OF SEA-LEVEL RISE

Over the twentieth century, global sea level rose about 17 cm (or1.7 mm/year) While this change may seem small, it has had many significant

TABLE 9.2 Summary of Sea-Level Rise Impacts on Socioeconomic Sectors

in Coastal Zones (© Reprinted with permission fromNicholls, 2010) TheseImpacts Are Overwhelmingly Negative

Impeded Drainage

effects, such as reducing the return periods of extreme water levels (Zhang

et al., 2000; Mene´ndez and Woodworth, 2010) and promoting an erosivetendency for coasts (Bird, 1985, 2000) However, linking sea-level risequantitatively to impacts is difficult as the coastal zone has been subjected tomultiple drivers of change over the twentieth century (Nicholls et al., 2009;Wong et al., 2014) Good data on rising sea levels has only been measured in

a few locations, and growing coastal populations and infrastructure haveincreased the exposure available to damage In addition, adaptation hasoccurred and, for example, flood defences have often been upgraded sub-stantially, especially in those (wealthy) places where there are long-termsea-level measurements (e.g., Ruocco et al., 2011) Most of these defenceupgrades coincide with the expanding populations and wealth in the coastalflood plain and changing attitudes to risk Hence, RSLR may not have beenconsidered in the design Equally, impacts can be promoted by processesother than sea-level rise (Table 9.1) For example, widespread humanreduction in sediment supply to the coast must contribute to the observederosional changes around the world and this probably dominates erosion inmany locations (Bird, 1985; Syvitski et al., 2009) Hence, while globalsea-level rise is a pervasive process, other processes obscure its link toimpacts, except in some special cases; most coastal change in the twentiethcentury was a response to multiple drivers of change

There have certainly been impacts from RSLR resulting from subsidence(Nicholls, 2010) Notable sites include the iconic city of Venice, which willshortly be protected by the MOSES storm surge barriers (see Horn, in thisvolume), and the Mississippi delta where thousands of square kilometers ofintertidal coastal marshes and adjacent lands were converted to open water inthe last 50 years There are also significant impacts of RSLR in and aroundsubsiding coastal cities (e.g.,Figure 9.3), in terms of increased waterlogging,flooding and submergence, and the resulting need for adaptation/managementresponses

These empirical observations also provide lessons for adaptation ing areas with a low population density were often abandoned, such as aroundGalveston Bay, Texas, and south of Bangkok, Thailand However, most of themajor developed areas that were impacted by RSLR have been defended andcontinue to experience population and economic growth (Nicholls, 2010) Thisincludes areas where the change in RSLR was rapiddseveral meters overseveral decades However, there are exceptions such as New Orleans (Grossiand Muir-Wood, 2006); its population peaked in 1965 at more than 625,000immediately before Hurricane Betsy flooded part of the city Before HurricaneKatrina in 2005, its population was about 500,000 Subsequently, the popu-lation has yet to recover to pre-Katrina levels, even though US$15 billion hasbeen invested to significantly upgrade defences (completed 2011) The future

Subsid-of New Orleans will be instructive: Does it prosper or continue to declinebehind the new defences and what are the reasons?

Observations since 1900 reinforce the importance of understanding theimpacts of sea-level rise in the context of multiple drivers of change; this willremain true under more rapid rises in sea level RSLR due to human-inducedsubsidence is of particular interest, but this remains relatively unstudied using

a systems approach Observations also emphasize the ability to protect againstRSLR, especially for the most densely populated areas, such as the subsidingAsian megacities or urban areas around the southern North Sea

9.6 FUTURE IMPACTS OF SEA-LEVEL RISE

The future impacts of sea-level rise will depend on a range of factors,including: (1) the magnitude of sea-level rise, (2) the coastal physiography, (3)the level and manner of coastal development, and (4) the success (or failure) ofadaptation Assessments of the future impacts of sea-level rise have takenplace on a range of scales from local to global They all suggest large potentialimpacts consistent withTable 9.1, especially increases in inundation, flooding,and storm damage (e.g.Nicholls et al., 2008) Recent studies of flood risk (i.e.,expected annual damages) under sea-level rise all emphasize that impactscould be catastrophic when assuming no adaptation (Hallegatte et al., 2013;Hinkel et al., 2014) However, if defences are upgraded and other adaptationtakes place, problems are more limited and possibly almost totally avoided.This stresses the importance of understanding adaptation

In absolute numbers, East, South-East and East Asia, and Africa appear to

be most threatened by sea-level rise (Figure 9.4) Vietnam and Bangladeshappear especially threatened due to large absolute and relative populations inlow-lying deltaic plains There are also large absolute threatened populations

in India and China In Africa, Egypt (the Nile Delta) and Mozambique are twopotential hotspots for impacts due to sea-level rise Hotspots also exist outsidethese regions, such as Guyana, Suriname, and French Guiana in SouthAmerica There will be significant residual risk in other coastal areas of theworld, such as around the southern North Sea, and major flood disasters arepossible in many coastal regions Small island regions in the Pacific, IndianOcean, and Caribbean stand out as being especially vulnerable to sea-level riseimpacts (Nurse et al., 2014) The populations of low-lying island nations, such

as the Maldives, Kiribati, or Tuvalu, face the real prospect of increasedflooding, submergence, salinization, and forced abandonment

9.7 MITIGATION OF SEA-LEVEL RISE

Climate mitigation can slow the global rise in sea level and reduce its impacts.Given the strong inertia of sea-level rise, mitigation stabilizes the rate

of sea-level rise (rather than stabilizing sea level itself) (Wong et al., 2014).Hence, even with mitigation, sea-level rise will continue and remain a challengefor generations to come (Church et al., 2013) This has been termed

the “commitment to sea-level rise,” which leads to a “commitment to adapt

to sea-level rise” with fundamental implications for long-term human use of thecoastal zone (Nicholls et al., 2007) Hence, adaptation and mitigation arecomplimentary policy responses for climate change in coastal areas.The fundamental goal of mitigation in the context of coastal areas is to reduce therisk of passing irreversible thresholds concerning the breakdown of the twomajor ice sheets of Greenland and Antarctica, thus constraining the commitment

to sea-level rise to a rate and ultimate rise which can be adapted to at a reasonableeconomic and social cost This requires consideration of sea-level rise beyond

2100, which is increasingly being investigated (Church et al., 2013) However,appropriate mixtures of mitigation and adaptation remains to be assessed.More locally, mitigation of human-induced subsidence also needs to beconsidered in susceptible areas, as already discussed This translates intomeasures to control/reduce groundwater extraction and manage water levels,which have been successfully implemented in a number of cities to date, such

as Shanghai, Osaka, and Tokyo (Kaneko and Toyota, 2011) This expertiseneeds to be transferred more widely to actively subsiding areas such as Jakarta,

or sites where these issues are likely to emerge However, while subsidencecan be largely reduced as with climate-induced sea-level rise, it cannot beentirely avoided, and some adaptation to subsidence will be required

9.8 ADAPTATION TO SEA-LEVEL RISE

Adaptation to sea-level rise involves responding to both mean and extremerise It is a complex process with multiple dimensions that different authorscharacterize differently The overall field of climate adaptation is also evolving

FIGURE 9.4 Regions most vulnerable to coastal flooding and sea-level rise At highest risk are coastal zones with dense populations, low elevations, appreciable rates of subsidence, and/or inadequate adaptive capacity From Nicholls and Cazenave (2010).

rapidly (e.g., Klein et al., 2014), and this is influencing coastal adaptation,even though coastal adaptation is one of the more mature sectors It isimportant to distinguish autonomous (or spontaneous) adaptation versusplanned adaptation One can also distinguish proactive versus reactive plannedadaptation Given the large and rapidly growing concentration of people andactivity in the coastal zone, autonomous adaptation processes alone will not beable to cope with sea-level rise Further, adaptation in the coastal context iswidely seen as a public rather than a private responsibility (Klein et al., 2000).Therefore, all levels of government have a key role in developing and facili-tating appropriate adaptation measures (Tribbia and Moser, 2008).

It is worth noting that society has tended to react to coastal events anddisasters rather than anticipate them In adapting to sea-level rise we are trying

to promote proactive adaptation, where appropriate There is significant scopefor anticipatory adaptation on coasts as many adaptation decisions have long-term (10e100 years) implications (e.g., Hallegatte, 2009) Examples ofanticipatory adaptation in coastal zones include upgraded flood defences anddrainage systems, higher elevation designs for new coastal infrastructure such

as fill levels for land claim and coastal bridges, building standards/regulations

to promote flood proofing and resilience, and building setbacks to preventdevelopment in areas threatened by erosion and flooding

The following section considers adaptation strategies and options, tation frameworks, adaptation selection, and adaptation experience

adap-9.8.1 Adaptation Strategies and Options

Adaptation can be classified in a variety of ways: one of the most widelyfollowed approaches is the Intergovernmental Panel on Climate Change(IPCC) typology of planned adaptation strategies (IPCC CZMS, 1990; Bijlsma

et al., 1996; Linham and Nicholls, 2010) (Figure 9.5):

l (Planned) Retreatdall natural system effects are allowed to occur andhuman impacts are minimized by pulling back from the coast via land useplanning, development controls, planned migration, etc (e.g.,Figure 9.6);

l Accommodationdall natural system effects are allowed to occur and man impacts are minimized by adjusting human use of the coastal zone viachanging land use/crop types, flood resilience measures, warning systems,insurance, etc (e.g.,Figure 9.7);

hu-l Protectiondnatural system effects are controlled by soft or hard barriers(e.g., nourished beaches and dunes, or seawalls), reducing human impacts

in the zone that would be impacted without protection (e.g.,Figure 9.8).Individually, there are a huge number of potential adaptationoptions Examples linked to each natural system impact are provided inTable 9.1.The concept of “attack” has been suggested as a strategy againstsea-level rise (e.g.,RIBA and ICE, 2010) This is consistent with land claim and