1

Vulnerability and Adaptation Assessments Hands-On Training Workshop

for the Africa Region

Global Sea-Level Rise: Analytical Approaches

Maputo, Mozambique18-22 April 2005

Julie Richards and Robert NichollsUniversity of Southampton, UK

julie.richards@soton.ac.uk

2

OutlineSea-level rise (SLR)

PredictionsScenariosGlobal processesLocal uncertaintiesImpacts

Shoreline management and adaptationMethods to assess impacts of SLR

Levels of assessmentScreeningVulnerability Planning

Review of African region situationModelsData sources

3

Current Global Predictions of Sea-Level Rise

TAR range for global-mean rise in sea level is between 9 cm and 88 cm by 2100

Change outside this range is possible, especially if Antarctica becomes a significant source

There is a “commitment to sea-level rise”even if atmospheric greenhouse gas concentrations are stabilised

4

Global-Mean Sea-Level Rise1990 to 2100 (SRES scenarios)

5

Processes Controlling Sea-LevelChange

Relative sea-level changes

6

Global Components of Sea-Level Rise

Ocean volume controlled by:Ocean temperature – thermal expansion

Melting of land-based iceSmall glaciersGreenlandAntarctica

The hydrological cycle (including human influence)

7

Uncertainty in Local Predictions

Relative SLR: global and regional components plus land movement

Land uplift will counter any global SLRLand subsidence will exacerbate any global SLROther dynamic oceanic and climatic effects cause regional differences (oceanic circulation, wind and pressure, and ocean-water density differences add additional component)

8

Sea-Level Rise at New York City1850 to 2100

6

8 S

ea L

evel

(m)

1850 1900 1950 2000 2050 2100 Time (yrs)

Observations Scenarios

IPCC TAR range due to SRES emission scenarios

9

Land Subsidence

10

Other Climate Change(Hurricane Andrew)

11

Impacts of Sea-Level Rise

Why is SLR important?

Physical impacts

Socio-economic impacts

Impact assessment

12

Elevation and Population Density Maps for Southeast Asia

13

Population and Population Density vs. Distance and

Elevationin 1990

14

Coastal Megacities (> 8 million people)Forecast for 2010

Istanbul

LagosLima

Buenos Aires Rio de JaneiroMadras

KarachiJakarta

Calcutta

MumbaiBangkok

ManilaShanghai

Osaka

Tokyo

Seoul

TianjinDhaka

New York

Los Angeles

15

National Vulnerability Profiles

ANTIGUA

WITH MEASURES

WITH MEASURES

NO MEASURES

NO MEASURES

peopleaffected

peopleaffected

protectioncosts

protectioncosts

peopleat risk

peopleat risk

wetlandat loss

wetlandat loss

landat loss

landat losscapita l

valueat loss

capita lvalueat loss

peopleat risk

peopleat risk

ARGENTINA

NIGERIA

VENEZUELA

based on expert judgement

based on analyses

LOW

Vulnerability profile classes

MEDIUMHIGHCRITICAL

URUGUAY

TONGA

SEYCHELLES

SENEGAL

POLAND

NEVIS

NETHERLANDS

MAURITIUS

MARSHALLS

KIRIBATI

JAPAN

GUYANA

EGYPT

BENIN

BANGLADESH

16

Biogeophysical Effects of Sea-Level Rise

Displacement of coastal lowlands and wetlands

Increased coastal erosion

Increased storm and flood damage

Salinisation of surface and ground waters

Plus others

17

Socio-Economic Impacts

• Loss of property and land• Increased flood risk / loss of life • Damage to coastal protection works and other

infrastructure• Loss of renewable and subsistence resources• Loss of tourism, recreation and coastal habitats• Impacts on agriculture and aquaculture through

decline in soil and water quality

18

Definition of Impacts

Potential impacts

Sea-level rise

Initial impacts

Residual impacts

Reactive adaptation

Anticipatory adaptation

19

Shoreline Management and Adaptation

No active intervention(Project appraisal methods)

(Flood plain mapping and flood warnings)

Improving awareness and preparedness

Reversing maladaptive trends

Managed realignmentRetreatEnhancing adaptability

Advance the lineAccommodateIncreasing flexibility

Hold the lineProtectIncreasing robustness

Shoreline Management (Defra)

Coastal Adaptation (IPCC)

Proactive Adaptation

20

Responding to Coastal Change(including sea-level rise)

Retreat

Accommodation

Protect SoftHard

21

Shoreline Management and Adaptation

No active intervention(Project appraisal methods)

(Flood plain mapping and flood warnings)

Improving awareness and preparedness

Reversing maladaptive trends

Managed realignmentRetreatEnhancing adaptability

Advance the lineAccommodateIncreasing flexibility

Hold the lineProtectIncreasing robustness

Shoreline Management (Defra)

Coastal Adaptation (IPCC)

Proactive Adaptation

22

Methods to Assess Impacts of Sea-Level Rise

Develop SLR scenariosLevels of assessmentScreening assessmentVulnerability assessment

ErosionFloodingCoastal wetland loss

Planning assessment

23

Coastal Vulnerability andRisk Assessment

Three levels of assessmentScreening assessment (3-6 months)Vulnerability assessment (1-2 years)Planning assessment (ongoing)

24

Screening AssessmentRapid assessment to highlight possible impacts of a SLR scenario and identify information/data gapsQualitative or semi-quantitativeSteps

1. Collection of existing coastal data2. Assessment of the possible impacts of a 1-m

SLR3. Implications of future development4. Possible responses to the problems caused by

SLR

25

Step 1: Collection of Existing Data

Topographic surveysAerial/remote sensing images – topography/land coverCoastal geomorphology classificationEvidence of subsidenceLong-term relative SLRMagnitude and damage caused by floodingCoastal erosionPopulation densityActivities located on the coast (cities, ports, resort areas and tourist beaches, industrial and agricultural areas)

26

Step 2: Assessment of Possible Impacts of 1-m SLR

Four impacts are considered1. Increased storm flooding

2. Beach/bluff erosion

3. Wetland and mangrove inundation and loss

4. Salt water intrusion

27

Step 3: Implications of Future Developments

New and existing river dams and impacts on downstream deltas

New coastal settlements

Expansion of coastal tourism

Possibility of transmigration

28

Step 4: Responses to the SLR Impacts

Planned retreat (i.e., setback of defences)

Accommodate (i.e., raise buildings above flood levels)

Protect (i.e., hard and soft defences, seawalls, beach nourishment)

29

Screening Assessment Matrix Biophysical vs. Socio-Economic Impacts

Erosion

Flooding

Human Health

Fisheries

Socio-economic impacts

Others?

Salinisation

Inundation

Others?Financial Services

Water Supply

AgricultureHuman Settlements

Tourism

Biophysic-al Impact of Sea-Level Rise

30

Vulnerability Assessment

Susceptibility Resilience/Resistance

AutonomousAdaptation

Planned Adaptation

Natural Vulnerability

Biogeophysical Effects

Impact Potential Ability toPrevent or Cope

AutonomousAdaptation

PlannedAdaptation

Socio-EconomicVulnerability

Residual Impacts

AcceleratedSea-Level Rise

OtherClimatic and Non-Climatic

Stresses

Socio-Economic System

Natural System

31

BOUNDARYCONDITIONS

NATURAL SYSTEM

SENSITIVITY ADAPTIVE CAPACITY

SOCIO-ECONOMIC SYSTEM

SENSITIVITY ADAPTIVE CAPACITY

EXPOSURE

EXPOSURE

Future

Historic

The Co-Evolving Coastal System

32

Barriers to Conducting VAIncomplete knowledge of the relevant processes affected by SLR and their interactionsInsufficient data on existing physical conditionsDifficulty in developing the local and regional scenarios of future changesLack of appropriate analytical methodologiesVariety of questions raised by different socio-political conditions

33

Controls on Coastal Positionlittoral sediment

supply (±ve)sea-levelchange

antecedentphysiography

boundary conditions (external)

lower shorefacebackbarrier

uppershoreface

bypassingcr

oss-

shel

f

transportinlet

resuspension & inlet bypassingfluvial-delta inlet bypassing

coastal tract

B

DC

A

inner-shelf sand

mid-shelf mud

marine sand wedge

lagoon basin mud

34

Erosion70% of world’s sandy beaches lost

Integral response to changes in coastal system sediment budget

Use of the Bruun Rule

Limitations of the Bruun Rule

35

An Atoll

36

Bruun Rule

37

Bruun Rule (2)R=G(L/H)S

where: H = B + h*

R = shoreline recession due to a sea-levelrise S

h* = depth at the offshore boundaryB = appropriate land elevation L = active profile width between boundariesG = inverse of the overfill ratio

38

Limitations of the Bruun Rule

Only describes one of the processes affecting sandy beaches

Indirect effect of sea-level rise Estuaries and inlets maintain equilibrium Act as major sinksSand eroded from adjacent coastIncreased erosion rates

Response time – best applied over long timescales

39

FloodingIncrease in flood levels due to rise in sea level

Increase in flood risk

Increase in populations in coastal floodplain

Adaptation Increase in flood protectionManagement and planning in floodplain

40

Coastal Flood Plain

41

Global Incidence of Flooding No Sea-Level Rise

0

10

20

30 P

eopl

e Fl

oode

d (M

illion

s/yr

)

1990 2020s 2050s 2080sTime (years)

42

Vulnerable RegionsMid-estimate (45 cm) by the 2080s

C

A

C

B

PEOPLE AT RISK(millions per region)

> 50 million

10 - 50 million

< 10 million

region boundary

vulnerable island region

Pa cificOcea nSMALLISLANDS

Caribbea n

IndianOcea nSMALL ISLANDS

CBA

43

Reference (1990)Land unavailable for arable Agriculture (% cell)

Low climate change High climate change

Impacts of Flooding on Arable Agriculture in 2050 – No Adaptation

44

0

20

40

60

No Sea-Level Rise

Unmitigated Emissions

Kyoto Protocol

20% Emissions Reduction

30% Emissions Reduction

Global Impacts of Flooding in 2050 Effects of Mitigation

People flooded (Millions/yr)

45

The Thames Barrier

46

Flood Methodology

Relative Sea-LevelRise Scenarios

Raised Flood Levels

Global Sea-levelRise Scenarios

Size of Flood Hazard Zones

People in theHazard Zone

Subsidence

Storm SurgeFlood Curves

Coastal Topography

PopulationDensity

Protection Status(1in 10, 1 in100, etc.)

Average AnnualPeople Flooded,

People to Respond

(“EXPOSURE”)

(“RISK”)

Relative Sea-LevelRise Scenarios

Raised Flood Levels

Global Sea-levelRise Scenarios

Size of Flood Hazard Zones

People in theHazard Zone

Subsidence

Storm SurgeFlood Curves

Coastal Topography

PopulationDensity

Protection Status(1in 10, 1 in100, etc.)

Average AnnualPeople Flooded,

People to Respond

(“EXPOSURE”)

(“RISK”)

47

Ecosystem LossInundation and displacement of wetlands

E.g., mangroves, saltmarsh, intertidal areas

Areas provideFlood protectionNursery areas for fisheriesImportant for nature conservation

Loss of valuable resources, tourism

48

KEY: mangroves, o saltmarsh, x coral reefs

Coastal Ecosystems

49

(a) no hard defences (b) hard defences

Sea-Level Rise

Coastal Squeeze (of coastal wetlands)

50

Mangrove Swamp

51

Areas Most Vulnerable to Coastal Wetland Loss

52

Present day loss rate

High Climate Change

Low ClimateChange

Saltmarsh Losses to 2050

53

Wetland Loss Model Structure

Relative Rate of Sea Level

Rise Scenarios

Rate of Sea Level Rise Scenarios

Vertical Wetland

Response

Wetland Loss

Tidal Range

NoLoss

Coastal Geomorph

-ology

Migration Potential

Corrected wetland loss

Coastal Population

Density

Horizontal Migration Assessment

54

Wetland Vertical Response Model

RSLR* = RSLR/TRwhere:

RSLR = the rate of relative sea-level rise(meters/century)

TR = the mean tidal range on spring tides in meters

RSLR* > RSLR*crit lossRSLR* ≤ RSLR*crit no loss

55

Planning AssessmentOngoing investigation and formulation of policy

Requires information onRole of major processes in sediment budget

Including human influencesOther climate change impacts

Example of assessment from the UK

Combined flood hazard and erosion assessment

56

The ProblemCliff Protection Has Local and Wider Effects

57

ErosionOften Exported Alongshore

58

Coastal Flood RiskExacerbated by Declining Sediment Input

Beach evolution

Defence degradation/upgrades

Socio-economic changes

Sea-level rise

Increased storminess

Changing impacts

Sediments

Changing loads

59

Goals for Planning Assessment

For future climate and protection scenarios, explore interactions between cliff management and flood risk within sediment sub-cell (in Northeast Norfolk)

In particular, quantifyCliff retreat and associated impactsLongshore sediment supply/beach sizeFlood riskIntegrated flood and erosion assessment

60

Climate Change,Sea-Level Rise

Scenarios

RegionalWave/Surge

Models

Protection,Socio-economic

Scenarios

SCAPERegional

Morphological Model

SCAPE GISData Storage

FloodRisk Analysis

(LISTFLOOD-FP)

Cliff ErosionAnalysis

Scenarios

IntegratedCell-scale

Assessment

Analysis OverallAssessment

Climate Change,Sea-Level Rise

Scenarios

RegionalWave/Surge

Models

Protection,Socio-economic

Scenarios

SCAPERegional

Morphological Model

SCAPE GISData Storage

FloodRisk Analysis

(LISTFLOOD-FP)

Cliff ErosionAnalysis

Scenarios

IntegratedCell-scale

Assessment

Analysis OverallAssessment

Overall Method

61

Nearshore sandbank

Offshore sandbank

Bathymetry and Wave Modelling

62

TidesWaves

Wave transformation

Longshoresediment transport

Q3D shore shape

Inshore waves

Cross-shore erosion

Cross-shore shape

Cliff retreat

Section n+1

Beach volume

Inshore waves

Cross-shore erosion

Cross-shore shape

Cliff retreat

Section n

Beach volume

TidesWaves

Wave transformation

Longshoresediment transport

Q3D shore shape

Inshore waves

Cross-shore erosion

Cross-shore shape

Cliff retreat

Section n+1

Beach volume

Inshore waves

Cross-shore erosion

Cross-shore shape

Cliff retreat

Section n

Beach volume

TidesWaves

Wave transformation

Longshoresediment transport

Q3D shore shape

Inshore waves

Cross-shore erosion

Cross-shore shape

Cliff retreat

Section n+1

Beach volume

Inshore waves

Cross-shore erosion

Cross-shore shape

Cliff retreat

Section n

Beach volume

TidesWaves

Wave transformation

Longshoresediment transport

Q3D shore shape

Inshore waves

Cross-shore erosion

Cross-shore shape

Cliff retreat

Section n+1

Beach volume

Inshore waves

Cross-shore erosion

Cross-shore shape

Cliff retreat

Section n

Beach volume

SystemMorphologicalModel

SCAPE Model of Cliff Retreat

63

Future PolicyMaintain Defences, 6 mm/yr Sea-Level Rise

-150 -100 -50 00

5

10

15

20

25

30

355 year s tages

Reces s ion dis tance

Dis

tanc

e al

ong

base

line,

km

0 0.5 1 1.5 2 2.50

5

10

15

20

25

30

35Average over 50 years

Reces s ion rate (m/A)

H

B

M

T

O

C

S Sheringham

Cromer

OverstrandTrimmingham

Mundesley

Bacton

Happisburgh

64

-150 -100 -50 00

5

10

15

20

25

30

355 year s tages

Reces s ion dis tance

Dis

tanc

e al

ong

base

line,

km

0 0.5 1 1.5 2 2.50

5

10

15

20

25

30

35Average over 50 years

Reces s ion rate (m/A)

H

B

M

T

O

C

S

Do NothingOpen Coas t

Sheringham

Cromer

OverstrandTrimmingham

Mundesley

Bacton

Happisburgh

Future PolicyAbandon All Defences, 6 mm/yr Sea-Level Rise

65

-150 -100 -50 00

5

10

15

20

25

30

355 year s tages

Reces s ion dis tance

Dis

tanc

e al

ong

base

line,

km

-150 -100 -50 00

5

10

15

20

25

30

355 year s tages

Reces s ion dis tance

Dis

tanc

e al

ong

base

line,

km

Hold existing defences

Abandon all defences Sheringham

Cromer

OverstrandTrimmingham

Mundesley

Bacton

Happisburgh

Policy ComparisonMaximum Retreat at Abandoned Defences

66

Erosion Visualisation Protection Abandoned (10 year time steps)

67

Conclusions45 sea-level/wave/protection scenario combinations assessed

Used to assess implications for flood risk

Data management, visualisation, and stakeholder involvement used

Further improvements to the overall method are being developed

68

Review of African RegionCoast relatively undeveloped

Coastal hazards a concern

Rapidly growing coastal population

Data availability issues

Lack of long-term sea level data

69

Impacts and Costs for 1m Sea-Level Rise (1990)

>400 >41118 121350 25230 0.2Benin

>1400 >417000 523200 418000 2Nigeria

>1000 >21>500 >12>110 >1 6000 3.1Senegal

Adaptation/ protection costsMillion US$ %GNP

Capital value lossMillion US$ %GNP

Population affected1000s %

Land LossKm2 %

Country

70

The Nile Delta

71

ModelsDIVA: Dynamic and Interaction Vulnerability Assessment

Project: DINAS-Coast

RegIS2 : Development of a metamodel tool for regional integrated climate change managementCOSMORamCo

72

73

74

Data SourcesIPCC Data Distribution Centre

Sea level dataPermanent service for mean sea levelGLOSS – Global Sea-Level Observing System

Remotely sensed dataLand Processes Distributed Active Archive Centre (NASA)Shuttle radar topography mission

75

GLOSS Tide Gauges

76

GTOPO30Global Digital

Elevation Model

77

SRTM Data – Morocco and Gibraltar(vertically exaggerated)

78

Data Sources (2)Local observational data

Sea level measurementsElevation/topography Wave recordingAerial photographyHabitat mapping

79

Concluding RemarksSea-level rise could be a serious problem, but the uncertainties are largeImpacts are strongly influenced by human choiceReducing greenhouse gas emissions reduces but does not avoid sea-level rise impactsPreparing to adapt would seem prudent, in the context of multiple stresses and managing existing problems