Coastal Zone Management, Study notes of Engineering

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Coastal Zone Management

C O - C H A I R S

J. Gilbert (New Zealand)

P. Vellinga (Netherlands)

• PREFACE C O A S T A L Z O N E M A N A G E M E N T
• E X E C U T I V E SUMMARY
• PROPOSAL O F T H E C Z M - C H A I R M E N FOR F U T U R E ACTIVITIES
• 5.1 I N T R O D U C T I O N
  • 5.1.1 Importance of the Coastal Zone
  • 5.1.2 Existing Problems
  • 5.1.3 Global Climate Change
  • 5.1.4 Ecological Impacts of Sea Level Rise
  • 5.1.5 Social and Economic Impacts of Sea Level Rise
• 5.2 ADAPTIVE RESPONSES
  • 5.2.1 Coastal Management
  • 5.2.2 Retreat
  • 5.2.3 Accommodation
  • 5.2.4 Protection - 5.2.4.1 Hard Structural Options
    • 5.2.4.2 Soft Structural Options
• 5.3 E N V I R O N M E N T A L IMPLICATIONS O F ADAPTIVE RESPONSES
  • 5.3.1 Introduction
  • 5.3.2 Retreat
  • 5.3.3 Accommodation
  • 5.3.4 Protection
    • 5.3.4.1 Hard Structures
      • 5.3.4.2 Soft Structures
• 5.4 E C O N O M I C IMPLICATIONS
  • 5.4.1 Introduction
  • 5.4.2 Retreat
  • 5.4.3 Accommodation
  • 5.4.4 Protection - 5.4.4.1 Cost Estimates for Protection
• 5.5 SOCIAL A N D C U L T U R A L IMPLICATIONS 132 I P C C RESPONSE STRATEGIES WORKING GROUP REPORTS - 5.5.1 Introduction - 5.5.2 Retreat - 5.5.3 Accommodation - 5.5.4 Protection
  • 5.6 L E G A L A N D INSTITUTIONAL IMPLICATIONS
    • 5.6.1 Introduction
    • 5.6.2 Retreat and Accommodation
    • 5.6.3 Protection
  • 5.7 PRIORITIES F O R A D A P T I V E RESPONSES
    • 5.7.1 Introduction
    • 5.7.2 Priorities for Adaptation
      • 5.7.2.1 Science/Monitoring
      • 5.7.2.2 Information
      • 5.7.2.3 Planning
      • 5.7.2.4 Education and Community Participation
      • Developing Countries 5.7.3 Priorities for Implementing Adaptive Options in
      • 5.7.3.1 Retreat
      • 5.7.3.2 Accommodation
      • 5.7.3.3 Protection
    • 5.7.4 Criteria for Allocation of Resources
    • R E F E R E N C E S

PREFACE

A C K N O W L E D G M E N T S

The focus of the Coastal Zone Management Sub- group (CZMS) is on options for adapting to sea level rise and other impacts of global change on coastal areas. The C Z M S held workshops in Miami, Florida, and in Perth, Western Australia, to gener- ate information on available adaptive response op- tions and their environmental, economic, social, cultural, legal, institutional, and financial implica- tions. The countries that contributed to the work of the C Z M S by sending experts to these workshops are listed below. Special acknowledgments are ad- dressed to the United States and Australia for host- ing these workshops. The writing of this report was entrusted to Messrs. J. Dronkers, R. Misdorp, P. C. Schroder (the Netherlands), J.J. Carey, J.R. Spradley, L. Vallianos, J. G. Titus, L. W. Butler, Ms. K. L. Ries(UnitedStates), J. T. E. Gilbert, J. Camp- bell, Ms. J. von Dadelszen (New Zealand), M r. N. Quin, and Ms. C. McKenzie and Ms. E. James (Australia). We wish to recognize and thank all of the partici- pants and reviewers who contributed their time, energy, and knowledge to the preparation of this report. We hope that the report will help nations in beginning to prepare for the potential impacts of global climate change on their coastal areas.

P A R T I C I P A T I N G C O U N T R I E S

Algeria, Antigua and Barbuda, Argentina, Austra- lia, Bahamas, Bangladesh, Barbados, Benin, Brazil, Brunei, Canada, Chile, China, Colombia, Costa

Rica, Denmark, Egypt, Fiji, France, Fed. Rep. of Germany, Ghana, Greece, Guyana, India, Indo- nesia, Iran, Italy, Ivory Coast, Jamaica, Japan, Kenya, Kiribati, Liberia, Maldives, Mauritius, Mexico, Micronesia, the Netherlands, New Cal- edonia, N e w Zealand, Nigeria, Pakistan, Papua N e w Guinea, Philippines, Poland, Portugal, Sene- gal, Seychelles, South Korea, Spain, Sri Lanka, St. Pierre and Miquelon, St. Vincent and the Grena- dines, Thailand, Tonga, Trinidad and Tobago, Tu- nisia, Turkey, Tuvalu, United Kingdom, United States, USSR, Vanuatu, Venezuela, Vietnam, West- ern Samoa, Yugoslavia.

P A R T I C I P A T I N G I N T E R N A T I O N A L O R G A N I Z A T I O N S

Greenpeace, International Oceanographic C o m - mission ( I O C ) , Organization for Economic Coor- dination and Development ( O E C D ) , South Pacific Regional Seas Programme (SPREP), United N a - tions Environment Programme ( U N E P ) , United Nations Educational, Scientific and Cultural Orga- nization ( U N E S C O ) , World Meteorological Orga- nization ( W M O ).

— J. T. E. GILBERT & P. V E L L I N G A The Hague, A p r i l 1990

EXECUTIVE SUMMARY

R E A S O N S F O R C O N C E R N

Global climate change may raise sea level as much as one meter over the next century and, in some areas, increase the frequency and severity of storms. H u n - dreds of thousands of square kilometers of coastal wetlands and other lowlands could be inundated. Beaches could retreat as much as a few hundred meters and protective structures may be breached. Flooding would threaten lives, agriculture, live- stock, buildings, and infrastructures. Saltwater would advance landward into aquifers and up estu- aries, threatening water supplies, ecosystems, and agriculture in some areas. Some nations are particularly vulnerable. Eight to ten million people live within one meter of high tide in each of the unprotected river deltas of Ban- gladesh, Egypt, and Vietnam. Half a million people live in archipelagoes and coral atoll nations that lie almost entirely within three meters of sea level, such as the Maldives, the Marshall Islands, Tuvalu, Kiribati, and Tokelau. Other archipelagoes and is- land nations in the Pacific, Indian Ocean, and Ca- ribbean could lose much of their beaches and arable lands, which would cause severe economic and so- cial disruption. Even in nations that are not, on the whole, partic- ularly vulnerable to sea level rise, some areas could be seriously threatened. Examples include Sydney, Shanghai, coastal Louisiana, and other areas eco- nomically dependent on fisheries or sensitive to changes in estuarine habitats. As a result of present population growth and development, coastal areas worldwide are under in- creasing stress. In addition, increased exploitation

of non-renewable resources is degrading the func- tions and values of coastal zones in many parts of the world. Consequently, populated coastal areas are becoming more and more vulnerable to sea level rise and other impacts of climate change. Even a small rise in sea level could have serious adverse effects. The Coastal Zone Management Subgroup has ex- amined the physical and institutional strategies for adapting to the potential consequences of global climate change. Particular attention was focused on sea level rise, where most research on impacts has been conducted. The Subgroup also has reviewed the various responses and has recommended actions to reduce vulnerability to sea level rise and other impacts of climate change.

R E S P O N S E S

The responses required to protect human life and property fall broadly into three categories: retreat, accommodation, and protection. Retreat involves no effort to protect the land from the sea. The coastal zone is abandoned and ecosystems shift landward. This choice can be motivated by exces- sive economic or environmental impacts of protec- tion. In the extreme case, an entire area may be abandoned. Accommodation implies that people continue to use the land at risk but do not attempt to prevent the land from being flooded. This option includes erecting emergency flood shelters, elevat- ing buildings on piles, converting agriculture to fish farming, or growing flood- or salt-tolerant crops.

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136 I P C C^ RESPONSE^ STRATEGIES^ WORKING^ GROUP^ REPORTS

Protection involves hard structures such as seawalls and dikes, as well as soft solutions such as dunes and vegetation, to protect the land from the sea so that existing land uses can continue. The appropriate mechanism for implementation depends on the particular response. Assuming that land for settlement is available, retreat can be imple- mented through anticipatory land-use regulations, building codes, or economic incentives. Accom- modation may evolve without governmental action, but could be assisted by strengthening flood prepa- ration and flood insurance programmes. Protection can be implemented by the authorities currently responsible for water resources and coastal protec- tion. Improving scientific and public understanding of the problem is also a critical component of any response strategy. The highest priorities for basic research are better projections of changes in the rate of sea level rise, precipitation, and the frequency and intensity of storms. Equally important, but more often overlooked, is the need for applied re- search to determine which options are warranted, given current information. Finally, the available in- formation on coastal land elevation is poor. Maps for most nations only show contours of five meters or greater, making it difficult to determine the areas and resources vulnerable to impacts of a one-meter rise in sea level. Except for a few countries, there are no reliable data from which to determine how many people and how much development are at risk. There are many uncertainties, and they increase as we look further into the future.

E N V I R O N M E N T A L I M P L I C A T I O N S

Two-thirds of the world's fish catch, and many marine species, depend on coastal wetlands for their survival. Without human interference, (the retreat option), ecosystems could migrate landward as sea level rises, and thus could remain largely in- tact, although the total area of wetlands would de- cline. Under the protection option, a much larger proportion of these ecosystems would be lost, especially if hard structures block their landward migration.

Along marine coasts hard structures can have a greater impact than soft solutions. Hard structures influence banks, channels, beach profiles, sediment deposits and morphology of the coastal zone. Protective structures should be designed—as much as possible—to avoid adverse environmental impacts. Artificial reefs can create new habitats for marine species, and dams can mitigate saltwater in- trusion, though sometimes at the cost of adverse environmental impacts elsewhere. Soft solutions such as beach nourishment retain natural shore- lines; but the necessary sand mining can disrupt habitats.

E C O N O M I C I M P L I C A T I O N S

N o response strategy can completely eliminate the economic impacts of climate change. In the retreat option, coastal landowners and communities would suffer from loss of property, resettlement costs, and the costs for rebuilding infrastructure. Under ac- commodation, there would be changing property values, increasing damage from storms, and costs for modifying infrastructure. Under the protection option, nations and communities would face the costs of the necessary structures. The structures would protect economic development, but could adversely affect economic interests that depend on recreation and fisheries. A n annex of the Coastal Zone Management Sub- group Report shows that if sea level rises by one meter, about 360,000 kilometers of coastal defenses would be required at a total cost of U.S.$500 billion by the year 2100. (This sum only reflects the mar- ginal or added costs and is not discounted.) This value does not include costs necessary to meet pres- ent coastal defense needs. The estimate does not include the value of the unprotected dry land or ecosystems that would be lost, nor does it consider the costs of responding to saltwater intrusion or the impacts of increased storm frequency. Therefore the overall cost will he considerably higher. A l - though some nations could bear all or part of these costs, other nations—including many small island states—could not. To ensure that coastal development is sustain- able, decisions on response strategies should be

138 I P C C^ RESPONSE^ STRATEGIES^ WORKING^ GROUP^ REPORTS

infrastructure and coastal defenses should in- clude consideration of sea level rise and other impacts of climate change. It is sometimes less expensive to incorporate these factors into the initial design of a structure than to rebuild it later. Actions in particular need of review in- clude river levees and dams, conversions of mangroves and other wetlands for agriculture and human habitation, harvesting of coral and increased settlement in low-lying areas.

4. Emergency preparedness and coastal zone re- sponse mechanisms need to he reviewed and strengthened. Efforts should be undertaken to develop emergency preparedness plans for re- ducing vulnerability to coastal storms, through better evacuation planning and the development of coastal defense mechanisms that recognize the impact of sea level rise.

I N T E R N A T I O N A L C O O P E R A T I O N

5. A continuing international focus on the im- pacts of sea level rise needs to be maintained. Existing international organizations should be augmented with new mechanisms to focus awareness and attention on sea level change and to encourage nations of the world to de- velop appropriate responses.

6. Technical assistance for developing nations should be provided and cooperation stimu- lated. Institutions offering financial support should recognize the need for technical assis- tance in developing coastal management plans, assessing coastal resources at risk, and increas- ing a nation's ability—through education, training, and technology transfer—to address sea level rise.

7. International organizations should support national efforts to limit population growth in coastal areas. In the final analysis, rapid pop- ulation growth is the underlying problem with the greatest impact on both the efficacy of coastal zone management and the success of adaptive response options.

R E S E A R C H , D A T A , A N D I N F O R M A T I O N

8. Research on the impacts of global climate change on sea level rise should be strength- ened. International and national climate re- search programmes need to be directed at understanding and predicting changes in sea level, extreme events, precipitation, and other impacts of global climate change on coastal areas.

9. A global ocean-observing network should be developed and implemented. Member na- tions are strongly encouraged to support the efforts of the I O C , W M O , and U N E P to establish a coordinated international ocean- observing network that will allow for accu- rate assessments and continuous monitoring of changes in the world's oceans and coastal areas, particularly sea level change.

10. Data and information on sea level change and adaptive options should be made widely available. A n international mechanism should be identified with the participation of the parties concerned for collecting and ex- changing data and information on climate change and its impact on sea level and the coastal zone, and on various adaptive op- tions. Sharing this information with develop- ing countries is critically important for preparation of coastal management plans.

P R O P O S A L O F T H E C Z M C H A I R M E N F O R F U T U R E A C T I V I T I E S

Based on the views of the delegates and the recom- mendations of the Miami and Perth I P C C - C Z M S workshops, the chairmen of the C Z M Subgroup and their advisers have undertaken the task to facili- tate the implementation of the C Z M actions. They suggest that three parallel efforts be undertaken:

1. Data Collection. Efforts to build a current global data base on coastal resources at risk due to sea level rise need to be vigorously pursued. The I P C C - C Z M Subgroup has de- veloped a questionnaire that can serve as a first step in the collection of this information and in identifying the countries where additional work needs to be done. It is also suggested that a data base or monitoring system be set up which would provide access to and informa- tion on adaption techniques, and which could be maintained in an international or regional "clearing house."

2. International Protocol. Efforts should com- mence immediately on the development of an international protocol to provide a framework for international and multinational coopera- tion in dealing with the full range of concerns related to impacts of sea level rise and climate change impacts on the coastal zone. A proto- col is needed to both establish the interna- tional frames of reference as well as to establish a clear set of goals and objectives.

Possible elements contained in such a protocol are outlined in Table 5.1.

3. Organizational Requirements. A process should be set in motion to guide and assist countries, particularly developing countries in carrying out the I P C C - C Z M actions. For this purpose I P C C could consider the forma- tion of a small advisory group to assist in the development of more specific guidelines. Such an advisory group could be formalized at a later stage to support the secretariat for the parties to a future protocol on C Z M and sea level rise.

The goals and actions presented in this report are based on problems common to all coastal nations; their achievement can benefit significantly from co- ordination at the international level. The three activities described above are consid- ered crucial steps in realizing the full potential of the I P C C process. The Miami and Perth workshops demonstrated very clearly that many developing na- tions will not be able to respond effectively to the needs that have been identified without some form of assistance. Additionally, and in accordance with the primary action for the development of comprehensive coastal zone management plans, a timeline (Table 5.2) of essential actions for the formulation of such plans is suggested. Countries that do not currently have coastal management plans could use this timeline as a basis for their own planning process over the next decade.

T A B L E 5. 2 : Suggested Ten-Year Timeline for the Implementation of Comprehensive Coastal Zone Management Plans 1991 Designate (a) national coastal coordinating bodies, (b) national coastal work teams, and (c) an interna- tional coastal management advisory group to support the I P C C - C Z M Subgroup and assist national work teams

1991--1993^ Develop preliminary national coastal management plans; begin public education and involvement

1991--1993 (^) Begin data collection and survey studies of key physical, social, and economic parameters assisted by international advisory group. For example:

• Topographic information • Tidal and wave range
• Land use • Population statistics
• Natural resources at risk

1992 Adoption of a "Coastal Zone Management and Sea Level Rise" protocol, with a secretariat of the parties, supported by the international coastal management advisory group

1992--1995 Begin development of coastal management capabilities, including training programmes; strengthening of institutional mechanisms

1995 Completion of survey studies, including identification of problems requiring immediate solution and of possible impacts of sea level rise and climate change impacts on the coastal zone

1996 Assessment of the economic, social, cultural, environmental, legal, and financial implications of response options

1997 Presentation to and the reaction from public and policymakers on response options and response selection

1998 Full preparation of coastal management plans and modifications of plans as required

1999 Adoption of comprehensive coastal management plans and development of legislation and regulations necessary for implementation

2000 Staffing and funding of coastal management activities

2001 Implementation of comprehensive coastal zone management plans

T A B L E 5. 3 : Operational Costs for Implementation of CZM-Actions 1, 6, 10 Estimated funding to provide the necessary support to meet the year 2000 coastal zone management plan proposal: 1 120 consultant-months @ U.S.$10,000 per month = U.S.$ 1,200, Expenses and travel = U.S.$

= U.S.$

800,

2,000,

2 Training of 100 in-countries personnel to strengthen coastal zone technical and planning capabilities 100 people @ U.S.$30,000 each = U.S.$^ 3,000,

3 Expenses for secretariat and advisory group = u. s. $ 3,000,

4 Conferences & workshops = u. s. $ 1,000,

5 Contingency = u. s. $ 1,000,

Total for 5 years, 1992-1997 = U.S.$1 0,000,

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144 I P C C^ RESPONSE^ STRATEGIES^ WORKING^ GROUP^ REPORTS

have further suggested that extreme events may be- come more frequent as a result of climate change.^7 For example, increased ocean temperatures may re- sult in changes in the frequency, duration and inten- sity of tropical storms. Moreover, the effect of storm surges could be intensified by higher sea levels. Inundation of coastal areas is already com- mon during tropical storms and any increases in the extent or frequency of inundation may render nu- merous heavily populated areas marginal or unin- habitable. Because the global climate system is complex, our understanding of it may progress slowly. The exist- ing system for monitoring global sea level cannot yet detect significant changes. Considerable uncer- tainties remain about the nature, timing, and magni- tude of future sea level rise, and the local, national, and regional impacts of human-induced global cli- mate changes.

5.1.4 E C O L O G I C A L IMPACTS O F SEA L E V E L RISE

Working Group II^8 suggests that a rise in sea level could: (1) increase shoreline erosion; (2) exacerbate coastal flooding; (3) inundate coastal wetlands and other lowlands; (4) increase the salinity of estuaries and aquifers; (5) alter tidal ranges in rivers and bays; (6) change the locations where rivers deposit sedi- ment; and (7) drown coral reefs. Estuaries, lagoons, deltas, marshes, mangroves, coral reefs, and seagrass beds are characterized by tidal influence, high turbidity (except coral reefs) and productivity, and a high degree of human activ- ity. Their economic significance includes their im- portance for fisheries, agriculture, shipping, recreation, waste disposal, coastal protection, bio- logical productivity, and diversity. The direct effect of sea level rise in shallow coastal waters is an increase in water depth. Intertidal zones may be modified; mangroves and other coastal veg- etation could be inundated and coral reefs could be drowned. In turn, this may cause changes in bird life, fish spawning and nursery grounds, and fish and shellfish production. For example, coastal wet- lands provide an important contribution to com- mercial and recreational fisheries, with an annual economic value of over $10 billion in the United States alone.^9 Equally important is the contribution

of wetlands to commercial and subsistence fisheries in many coastal and island states. Table 5.4 lists the areas of coastal wetlands of "international impor- tance" for major regions of the world. In general, the effects on shallow coastal ecosys- tems are strongly determined by local conditions. A good understanding of the physical and biological processes and topography is required to forecast local impacts. But if the accumulation of sediments cannot keep pace with rising waters, or if inland expansion of wetlands and intertidal areas is not possible1 0^ (because of infrastructure or a steeply rising coast), major impacts could occur. The estuarine response to rising sea level is likely to be characterized by a slow but continually adjust- ing environment. With a change in estuarine vegeta- tion there could be an adjustment in the animal species living in and around the wetlands. Climate change may also provoke shifts in the hydrological regimes of coastal rivers and lead to increased dis- charge and sediment yields and, consequently, to increased turbidity. These changes, together with a rise in sea level, could modify the shape and location of banks and channels. If no protective structures are built, wetlands can migrate inland; however, a net loss of wetlands would still result.

5.1.5 S O C I A L A N D E C O N O M I C IMPACTS O F S E A L E V E L RISE

Many developing countries have rapid rates of pop- ulation growth, with large proportions of their pop- ulations inhabiting low-lying coastal areas. A one- meter rise in sea level could inundate 15 percent of Bangladesh,1 1^ destroy rice fields and mariculture of the Mekong delta, and flood many populated atolls, including the Republic of Maldives, Cocos Island, Tokelau, Tuvalu, Kiribati, the Marshall Islands, and Torres Strait Islands.1 2^ Shanghai and Lagos, the largest cities of China and Nigeria, lie less than two meters above sea level, as does 20 percent of the population and farmland of Egypt.1 3 Four highly populated developing countries, In- dia, Bangladesh, Vietnam, and Egypt, are especially vulnerable to sea level rise because their low-lying coastal plains are already suffering the effects of flooding and coastal storms. Since 1960, India and Bangladesh have been struck by at least eight tropi- cal cyclones, each of which killed more than 10,

T A B L E 5. 4 : Areas of Coastal Wetlands of International Importance* (^) in Sq km and As Percentage of Country Areas

in Sq km and As

A R E A O F (^) W E T L A N D A S % O F REGION WETLANDS I N K M (^2) T O T A L C O U N T R Y A R E A

1. North America, excluding Canada and USA 32330 1.
2. Central America (^25319) 0.
3. Caribbean Islands 24452 9.
4. South America Atlantic Ocean Coast (^158260) 1.
5. South America Pacific Ocean Coast 12413 0.
6. Atlantic Ocean Small Islands (^400) 3.
7. North and West Europe 31515 0.
8. Baltic Sea Coast 2123 0.
9. Northern Mediterranean 6497 0.
10. Southern Mediterranean 3941 0.
11. Africa Atlantic Ocean Coast 44369 0.
12. Africa Indian Ocean Coast 11755 0.
13. Gulf States 1657 0.
14. Asia Indian Ocean Coast 59530 1.
15. Indian Ocean Small Islands
16. South-East Asia 122595 3.
17. East Asia 102074 0.
18. Pacific Ocean Large Islands, excluding Australia and New Zealand 89500 19.

19. Pacific Ocean Small Islands — —

20. USSR 4191 0.

TOTALS 732921 0.

Source: " A Global Survey of Coastal Wetlands, Their Functions and Threats in Relation to Adaptive Responses to Sea Level Rise." Paper by Dutch Delegation to I P C C - C Z M Workshop, Perth, Australia, February 1990. '•' Based on: Directories of Wetlands, issued by I U C N / U N E P (1980-90), 120 countries, excluding among others Australia, Canada, New Zealand, USA.

Coastal Zone Management (^) 147

- Accommodation: Continued occupancy and use of vulnerable areas. - Protection: Defense of vulnerable areas, espe- cially population centers, economic activities, and natural resources.

5.2.2 R E T R E A T

Options for retreat include:

1. Preventing development in areas near the coast.

2. Allowing development to take place on the condition that it will be abandoned if necessary (planned phase out).

3. No direct government role other than through withdrawal of subsidies and provision of i n - formation about associated risks.

Governmental efforts to limit development gen- erally involve land acquisition, land-use restric- tions, prohibited reconstruction of property dam- aged by storms, and reductions of subsidies and incentives for development in vulnerable areas. Many nations have purchased large areas on the coast and designated them as nature reserves. Pre- venting development can reduce future expendi- tures for adaptation. India, Sri Lanka, Tonga, Fiji, Mauritius, Austra- lia, and the United States already require new build- ings be set back from the sea. These regulations could be modified to consider the future impacts from a rising sea level, but most nations would re- quire compensation for coastal property owners.1 7 The second option gives the government a more limited role, in that it lays out the "rules of the game"—the eventual transgression of the sea.1 8^ In- vestors are accustomed to evaluating uncertainty and can determine whether development should proceed, given the constraint. This approach can be implemented through (a) regulations that prohibit private construction of protective structures, or (b) conversion of land ownership to long-term or con- ditional leases that expire when the sea reaches a particular level or when the property owner dies. The third option would be to depend on the workings of the private market. Productive crop

and timber lands may be left to slowly and progres- sively deteriorate as a result of salt intrusion into the groundwater or by surface flooding. Wells and sur- face water exposed to saltwater intrusion would gradually be abandoned. Natural resources, such as mangroves, marshes, and coral reefs, would be left to their natural processes as sea level rises. Under this option, governments could take the more limited role of ensuring that all participants in potentially vulnerable areas have full knowledge about the expected sea level rise and its associated uncertainties. Development would presumably not occur if developers, lenders, and insurers were not willing to accept the risks. However, if people con- tinue to build in vulnerable areas, governments must be prepared to take the necessary actions to ensure public safety. For small island states, retreat does not offer a broadly applicable alternative. There would be little or no land for resettlement, in addition to loss of heritage and cultural upheaval.

5.2.3 A C C O M M O D A T I O N

The strategy of accommodation, like that of retreat, requires advanced planning and acceptance that some coastal zone values could be lost. Many coastal structures, particularly residential and small commercial buildings, could be elevated on pilings for protection from floods. To counter surging wa- ter and high winds, building codes could specify minimum floor elevations and piling depths, as well as structural bracing. Drainage could be modified. Storm warning and preparedness plans could be instituted to protect the affected population from extreme events. Where saltwater damages agri- cultural lands and traditional crops, salt-tolerant crops may be a feasible alternative. Fundamental changes in land use may be desirable, such as the conversion of some agricultural lands to aqua- cultural uses. Human activities that destroy the natural protec- tion values of coastal resources can be prohibited. Perhaps the most important controls would be to prohibit filling wetlands, damming rivers, mining coral and beach sands, and cutting mangroves. U n - developed land with sufficient elevation and slope can be set aside to accommodate natural re- establishment of wetlands and mangroves. Within

148 I P C C^ RESPONSE^ STRATEGIES^ WORKING^ GROUP^ REPORTS

deltaic areas, natural processes can be maintained by diverting water and sediment. In response to sa- linity intrusion into groundwater aquifers, manage- ment controls can be implemented to regulate pumping and withdrawal practices. Requiring private insurance coverage in vulner- able areas is an important method to compensate injuries and damages caused by natural disasters. It forces people to consider whether risks are worth taking and provides the necessary funds to repair damages and compensate victims.

5.2.4 P R O T E C T I O N

This strategy involves defensive measures and other activities to protect areas against inundation, tidal flooding, effects of waves on infrastructure, shore erosion, salinity intrusion and the loss of natural resources.1 9^ The measures may be drawn from an array of " h a r d " and "soft" structural solutions.2 0 They can be applied alone or in combination, de- pending on the specific conditions of the site. There is no single or generic "best solution," as each situation must be evaluated and treated on its particular merits. However, there are some basic steps in the selection of measures likely to produce the highest economic returns. First, those charged with planning, design or management respon- sibilities in the coastal zones should be cognizant of the potential for future sea level rise. Moreover, proposed plans should leave options open for the most appropriate future response. F o r example, many protection structures can be planned and de- signed with features that allow for future incremen- tal additions that, if needed, could accommodate increased water levels and wave action. This can often be done without significant additional costs in the initial investment. It should be noted that the capital costs associated with the " h a r d " set of options may prove a barrier to consideration of this option by developing coun- tries and small island states.

5.2.4.1 Hard Structural Options

Dikes, Levees, and Floodwalls are raised embank- ments or walls constructed for flood protection purposes. Depending on circumstances, internal

drainage may be accomplished by gravity flow, tide gates, or pumping systems.

Seawalls, Revetments, and Bulkheads protect i n - land properties from the direct effects of waves and storm tides. Seawalls and heavy revetments (sloping armored surfaces) are constructed along open coast areas to defend areas against severe wave attack. Lighter revetments and bulkheads usually serve as secondary lines of defense along open coast areas, or as first lines of defense along more sheltered interior shores with low to moderate wave exposure.

Groins are structures placed perpendicular to the shoreline. They generally extend from the land into the near shore zone and trap sediment moving along the shore in order to widen the beach or prevent it from eroding.

Detached Breakwaters are robust structures placed offshore, usually parallel to the shoreline, for the purpose of dissipating the energy of incoming waves to reduce both erosion and damage from storms.

Raising Existing Defensive Structures may be facili- tated through the incorporation of such a possibility in the initial design. Some dikes, levees, floodwalls, seawalls, revetments, and breakwaters can be easily raised and strengthened in the event of sea level rise or increased storm exposure.

Infrastructure Modifications may involve the eleva- tion of piers, wharves, bridges, and road and rail beds; modifications to drainage systems; reloca- tions of various facilities and the institution of flood-proofing measures.

Floodgates or Tidal Barriers, which are adjustable, dam-like structures, can be placed across estuaries to prevent the upstream flooding from storm tides. Such barriers are usually left open to avoid interfer- ing with existing flows.

Saltwater Intrusion Barriers in surface water streams can consist of locks or dams that directly block upstream penetration of saline water. Dams upstream of a salt penetration zone may be operated so that water released from the reservoirs at appro- priate times can act to minimize the upstream move-