Transcript 21-MET

2.1 Overview of Coastal Vulnerability Assessment
Level of
assessment
Timescale Precision
required
Prior
Other scenarios in
knowledge addition to SLR
Strategic level
(Screening
assessment)
2-3 months
Lowest
Low
Direction of change
Vulnerability
assessment
1-2 years
Medium
Medium
Likely socio-economic
scenarios and key
scenarios of key
climate drivers
Site-specific
level (Planning
assessment)
Ongoing
Highest
High
All climate change
drivers (often with
multiple scenarios)
Level of Assessment: Screening Assessment (I)
 Rapid assessment to highlight possible impacts of a sea level rise scenario and
identify information/data gaps
 Qualitative or semi quantitative
 Steps
1.
Collation of existing coastal data
2.
Assessment of the possible impacts of a 1-m sea level rise
3.
Implications of future development
4.
Possible responses to the problems caused by sea level rise
Step 1: Collation of Existing Data
 Topographic surveys
 Aerial/remote sensing images – topography/ land cover
 Coastal geomorphology classification
 Evidence of subsidence
 Long-term relative sea level rise
 Magnitude and damage caused by flooding
 Coastal erosion
 Population density
 Activities located on the coast (cities, ports, resort areas and tourist beaches,
industrial and agricultural areas)
Step 2: Assessment of Possible Impacts of 1m Sea Level Rise

Four impacts are considered

(i) Increased storm flooding

(ii) Beach/bluff erosion

(iii) Wetland and mangrove inundation and loss

(iv) Salt water intrusion
(i) Increased Storm Flooding
 Describe what is located in flood-prone areas;
 Describe historical floods, including location, magnitude and damage, the response
of the local people, and the response of government. How have policies toward
flooding evolved?.
(ii) Beach/bluff Erosion

Describe what is located within 300 m of the ocean coast.

Describe beach types.

Describe the various livelihoods of the people living in coastal areas such as
commercial fishers, international-based coastal tourism, or subsistence
lifestyles.

Describe any existing problems of beach erosion including quantitative data.
These areas will experience more rapid erosion given accelerated sea level rise.

For important beach areas, conduct a Bruun rule analysis (Nicholls, 1998) to
assess the potential for shoreline recession given a 1 m rise in sea level. What
existing coastal infrastructure might be impacted by such recession?
(iii) Wetland and Mangrove Inundation

Describe the wetland areas, including human activities and resources that
depend on the wetlands. For instance, are mangroves being cut and used, or do
fisheries depend on wetlands?

Have wetlands or mangroves being reclaimed for other uses, and is this likely to
continue?

Are these wetlands viewed as a valuable resource for coastal fisheries and
hunting or merely thought of as wastelands?
(iv) Salt Water Intrusion

Is there any existing problem with water supply for drinking purposes?

Does it seem likely that salinization due to sea level rise will be a problem for
surface and/or subsurface water?
With 1 m of sea-level rise,
most of the Hawaiian shoreline will
look like this
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
Step 4: Responses to the Sea Level Rise Impacts
 Planned retreat (i.e. setback of defenses)
 Accommodate (i.e. raise buildings above flood levels)
 Protect (i.e. hard and soft defenses, seawalls, beach nourishment)
Screening Assessment Matrix (Biophysical vs. Socioeconomic Impacts)
Biophysical Impact
of Sea
Level Rise Tourism
Inundation
Erosion
Flooding
Salinization
Others?
Socioeconomic impacts
Human
Settlements
Agriculture
Water
Supply
Fisheries
Financial
Services
Human
Health
Gender
Bruun Rule
R = G(L/H)S; where H=B + h*
R = shoreline recession due to a sea-level rise S
h* = depth at the offshore boundary
B = appropriate land elevation
L = active profile width between boundaries
G = inverse of the overfill ratio
Beach Profile in Equilibrium with Sea Level
Y
Eroded profile
X
Accreted profile
Y/X = 50 to 200….say, 100
1 m sea level rise = 100 m (~400 ft) shoreline recession
Depth of
closure
Limitations of the Bruun Rule
 Only describes one of the processes affecting sandy beaches
 Indirect effect of mean sea level rise

Estuaries and inlets maintain equilibrium

Act as major sinks

Sand eroded from adjacent coast

Increased erosion rates
 Response time – best applied over long timescales
Level of Assessment: Vulnerability Assessment (II)
Coastal Vulnerability Assessment

Vulnerability assessment (1-2 years)
 (i) Erosion
 (ii) Flooding
 (iii) Coastal wetland/ecosystem loss
 The aim of screening and vulnerability assessment is to scale
prioritization of concern and to target future studies, rather than to
provide detailed predictions
(i) Vulnerability Assessment: Beach Erosion
(ii) Vulnerability Assessment: Flooding
 Increase in flood levels due to rise in sea level
 Increase in flood risk
 Increase in populations in coastal floodplain
 Adaptation

Increase in flood protection

Management and planning in floodplain
Coastal Flood Plain
Flood Methodology
Global Sea-level
Rise Scenarios
Subsidence
Storm Surge
Flood Curves
Coastal
Topography
Relative Sea-Level
Rise Scenarios
Raised Flood Levels
Population
Density
Size of Flood
Hazard Zones
Protection Status
People in the
Hazard Zone
(“EXPOSURE”)
Average Annual
People Flooded,
People to Respond
(“RISK”)
(1in 10, 1 in100, etc.)
(iii) Vulnerability Assessment : Wetland/Ecosystem Loss
 Inundation and displacement of wetlands

e.g., mangroves, saltmarsh, intertidal areas

Wetland areas provide
 Flood protection
 Nursery areas for fisheries
 Important for nature conservation
 Loss of valuable resources, tourism
Areas Most Vulnerable to Coastal Wetland Loss
Coastal wetland Loss (Mangrove Swamp)
Coastal Squeeze (of coastal wetlands)
Coastal squeeze under sea-level rise: impact of development (Image: DCCEE, 2009)
Coastal Ecosystems at Risk
KEY:
mangroves, o saltmarsh, x coral reefs
Planning Assessment (III)
 On-going investigation of an specific area and formulation of policy

Requires information on
 Role of major processes in sediment budget
 Including human influences
 Other climate change impacts
 Combined flood hazard and erosion assessment
How do beaches respond to sea level rise?
…they erode…
How do people respond to eroding beaches?
…they armor…
…and how do beaches respond to armoring?
…they disappear…
3. Do Not Armor Public Lands
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, quantify

Cliff retreat and associated impacts

Longshore sediment supply/beach size

Flood risk

Integrated flood and erosion assessment
Method for Planning Assessment
Scenarios
Climate Change,
Sea-Level Rise
Scenarios
Protection,
Socio-economic
Scenarios
Overall
Assessment
Analysis
Regional
Wave/Surge
Models
SCAPE
Regional
Morphological
Model
Flood
Risk Analysis
(LISTFLOOD-FP)
SCAPE GIS
Data Storage
Cliff Erosion
Analysis
Integrated
Cell-scale
Assessment