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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)
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Sea-Level Rise at New York City1850 to 2100
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8 S
ea L
evel
(m)
1850 1900 1950 2000 2050 2100 Time (yrs)
Observations Scenarios
IPCC TAR range due to SRES emission scenarios
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Land Subsidence
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Other Climate Change(Hurricane Andrew)
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Impacts of Sea-Level Rise
Why is SLR important?
Physical impacts
Socio-economic impacts
Impact assessment
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Elevation and Population Density Maps for Southeast Asia
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Population and Population Density vs. Distance and
Elevationin 1990
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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
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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
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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
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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
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Definition of Impacts
Potential impacts
Sea-level rise
Initial impacts
Residual impacts
Reactive adaptation
Anticipatory adaptation
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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
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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
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Coastal Vulnerability andRisk Assessment
Three levels of assessmentScreening assessment (3-6 months)Vulnerability assessment (1-2 years)Planning assessment (ongoing)
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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
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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)
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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
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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
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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)
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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
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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
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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
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An Atoll
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Bruun Rule
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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
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Coastal Flood Plain
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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
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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
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