The document discusses the impacts of climate change on coastal areas, highlighting the inevitability of sea-level rise due to warming oceans and melting ice. It emphasizes the need for improved scientific understanding and adaptive management strategies, as well as the uncertainties surrounding future sea-level rise and its consequences. A case study in Falmouth, MA, outlines proactive measures that can be taken to mitigate coastal erosion and enhance resilience in the face of rising seas.

1. Changing Climate, Changing Coasts
Rob Thieler
U.S. Geological Survey
Woods Hole, MA

2. Outline
• Scientific and management dimensions of sealevel change
• Results and implications of recent sea-level rise
assessments
• Options and potential impacts of different
shoreline adaptation strategies
• How one town is starting to address the issue

3. The U.S. Coastal Crisis – Coastal population
and development are increasingly
vulnerable to coastal hazards
• Erosion affects all 30 coastal states
• 60-80% of coast is eroding
• Erosion caused by diverse, complex
processes
• Coastal populations have doubled
• >50% live along coasts
• Infrastructure about $9 trillion

4. We need better science* to prepare our local responses to
climate change, especially in our coastal areas.
(David Carter, Delaware Coastal Management)
*science = better understanding of processes + better situation awareness

5. Key Principles Regarding Sea-level Rise
• There is no debate over sea-level rise
When the climate warms, oceans increase in volume and
land-based ice melts
• Attribution of sea-level rise is largely irrelevant
For example, if the world stopped emitting GHGs tomorrow,
sea level would continue to rise for several centuries
• The major questions are how much, and how fast?
The answers depend in part on our future emission
pathways, and the future behavior of large ice sheets

6. Land water
storage changes
Ocean currents change
Land can
rise or sink
Warm water
expands
Ice melts into
the ocean
(IPCC, 2001)

7. Past, Current and Projected Global
Temperature
The last 10,000 years have been ideal for
the development of human societies.
This has been a unique time during
which climate varied very little and
enabled humankind to flourish.

8. Sea-level rise rates since the Last Glacial
Maximum
mwp-Ib
Global delta initiation
(Stanley and Warne, 1994)
U.S. Atlantic, U.K.
wetland initiation;
barrier island stability
(Shennan and Horton, 2002;
Engelhart et al., 2009)
Rate of SLR (mm/yr)
mwp-Ia
Thousands of 14C years before present
(SLR rate based on Fairbanks, 1989; ice extent from Dyke, 2004)

9. “Projections”
(Rahmstorf, 2007)
“Geologic past”
(Fairbanks, 1989;
Horton et al. 2009)
“Instrumental record”
(Church and White, 2006)
Years before present
Rate of SLR (mm/yr)
Past, present, and potential future rates of
sea-level rise

10. Projected Sea-level Rise
Recent expert assessment
(n=90 experts)
0.4-0.6 m for RCP 3-PD
0.7-1.2 m for RCP 8.5
IPCC AR5
(Horton et al., 2013)
(modified after Rahmstorf, 2007; AR4 data from Bindoff, 2007)
(courtesy Aslak Grinsted; AR5 projections from IPCC, 2013)

11. Mid-Atlantic Assessment of Potential
Dynamic Coastal Responses to Sea-level Rise
Bluff erosion
Overwash
Island Breaching
(Gutierrez et al., 2009)
Threshold Crossing

12. Dynamic Equilibrium of Beaches
Sediment supply
Relative sealevel change
Location and
shape of the
beach
Wave energy
(after Pilkey and Thieler, 1992)

13. Common responses to an eroding coastline
Hard stabilization
• Seawalls, groins,
breakwaters, etc.
Soft stabilization
• Beach nourishment
Relocation or retreat
• Move back from
eroding shorelines
(after Pilkey and Thieler, 1992)

14. Hard stabilization
• Advantages
• Most dependable way to save
beachfront property
• Disadvantages
•
•
•
•
Degrades the recreational beach
Reduces beach access
Costly
Unsightly
(after Pilkey and Thieler, 1992)

15. Modes of beach loss by seawalls
Placement
• Seawall built on
the beach
Passive
• Beach continues to
retreat and
narrows in front of
the seawall
Active
(after Pilkey and Thieler, 1992)
• Seawall directly
causes erosion

16. Two alternative scenarios for longterm shoreline change
(Pilkey and Thieler, 1992)

17. Related impacts of hard stabilization
Changes to alongshore
sediment transport
Reduction in sediment
delivery to beach system

18. Informing Decisions in a Changing Climate
National Research Council (2009)
The end of “Climate Stationarity” requires that
organizations and individuals alter their standard
practices and decision routines to take climate
change into account. Scientific priorities and
practices need to change so that the scientific
community can provide better support to
decision makers in managing emerging climate
risks.
• Decision makers must expect to be surprised
because of the nature of climate change and
the incompleteness of scientific
understanding of its consequences.
• An uncertainty management framework
should be used because of the inadequacies
of predictive capability.

19. Sea-level rise impacts: A multivariate problem with
uncertainties everywhere
Driving
Forces
Climate Change
&
Sea Level
Rise
Groundwater
Impact
Habitat Loss
Wetland Loss
Physical
& Biological
Processes
Potential
Impacts
Coastal Erosion
Initial
Conditions
Safety
Inundation
Management
Decisions

20. Some things to consider…
• Options that maintain future flexibility
• Magnitude and timing of future climate change and our responses to it are
uncertain
• Holistic examination of potential impacts
• Geologic, biologic, economic, social...
• Expectations of your coastal zone (resources, tourism, aesthetics,
navigation, etc.)
• Time horizon
• How long should something last? Forever? Until you have a better plan to
address the problem? The next big storm? Two feet of sea-level rise?
• Risk tolerance
• Scale with size, value, time
• Implications of failure or over-planning/building
• Protocols for what happens after large events
• Because there will be a "next time"

21. Understanding Where We Are, and
Where We Could Go
www.falmouthmass.us/depart.php?depkey=coastal

22. Sediment Source Area
Longshore Transport
Eastern Limit of Moraine
0
1
2
kilometers
Falmouth South Shore
USGS 1995 photography
3

23. Groins
Rapid
erosion
Jetties
Groins,
overwash
Armored
bluffs
Falmouth South Shore
USGS 1995 photography
0
1
2
3
kilometers
About 50% of south coast parcels are armored. Half are Town parcels.
There are 70 groins, 10 jetties, and 94 revetments on the south coast.

24. ~1950s
Nobska Point
(NOAA)
(courtesy RJNick, www.noticetoairmen.com)
2000s

25. Falmouth Heights, 1897
Falmouth Heights, 2000

26. Falmouth South Shore Erosion Rates
0.5
Erosion Rate (ft/yr)
0.0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
1845-1890
1800s-1948
Year Interval
1975-1994

27. Green Pond
Shoreline Change
Since 1845
~130 ft
~550 ft
• Sediment supply
decreased
• Uplands armored,
beaches narrowed
• Barrier has
migrated into the
pond

28. Vision for Falmouth’s Coast
(for the next 50-100 years)
• Beaches and dunes wide enough for protection from storms and public
access and use.
• Sufficient sand in the coastal system.
• Sustained and enhanced water quality, habitat and fisheries resources.
• A minimum of hard structures (groins, seawalls, etc.).
• Public infrastructure will be relocated from the immediate coast.
• A proactive approach to shoreline management to prevent problems and
provide a response protocol when shoreline damage occurs.

29. Achieving the Vision
for Falmouth’s Coast
• Acquire coastal land for open space.
• Move or change vulnerable public infrastructure. Plan future
infrastructure (e.g., roads, sewers) wisely.
• Conduct beach nourishment experiments at key “source” locations.
• Remove unnecessary, hazardous, or damaging coastal armoring
structures.
• Create effective sand management systems.
• Improve regulations to protect coastal systems and beaches.
• Encourage protection of valuable coastal assets such as unarmored
bluffs.

30. Summary
• The coast as we know it today is a product of sea-level
rise
• Major changes are coming to the coast, ecosystems,
and resources
• Future sea-level rise is a certain impact
•
We have already made a commitment to several centuries of rise
• Future sea-level rise is an uncertain impact
•
•
Rates and magnitudes poorly constrained
Societal response unknown
• Informed preparation is important