CSE Capabilities

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2007 NCBIWA Conference
SLR Impacts on Beaches and Coastal
Wetlands Problems You May Not Know
Timothy W. Kana Ph.D. Bart J. Baca Ph.D.
Peak Annual Tide North Inlet
C o a s t a l S c i e n c e E n g i
n e e r i n g
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NCBIWA 2007
Presentation Outline

• EPA SLR Impacts Case Studies Still Relevant!
• Charleston Physical Impacts
• Charleston Wetlands Impacts
• New Jersey Wetlands Impacts
• Impacts - Storm Tide Levels
• Impacts - Barrier Beaches
• Impacts Tidal Wetlands
• Impacts Daily Life!

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NCBIWA 2007
US EPA-sponsored research Case Study Charleston
SC Physical Impacts Beaches Storm Tides Kana,
Michel, Hayes Jensen 1984 (in Barth Titus
1984) Case Study Charleston SC Wetlands Kana,
Baca Williams 1986 EPA Report
230-10-85-014 Case Study Little Egg Harbor
NJ Wetlands Kana, Eiser, Baca Williams
1988 EPA Report 230-05-86-013
Scenarios Prepared By Goddard Institute for
Space Studies c/o Dr. James Hansen
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Methods

• Existing Conditons Mapped
• DTM Developed
• Key Elevations
• MHW
• 10-yr Storm Surge
• 100-yr Storm Surge
• gt 100-yr Surge

SLR Scenarios 100 years Baseline 25 cm (0.8
ft) Low 90 cm (2.9 ft) Middle 160 cm (5.2
ft) High 230 cm (7.6 ft)
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NCBIWA 2007
20th Century Annual Rates of Relative SLR
(mm/yr)
Wilmington Charleston 19 24 cm/century
In Charleston Eustatic _at_ 0.12 cm/yr
Subsidence _at_ 0.13 cm/yr
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Charleston DTM Modeling Shift Of Flood
Boundaries
Baseline SLR Rises _at_ Same Rate
Low Scenario SLR Rises _at_ 2.5X Rate
Mid To High Scenario SLR Rises _at_ 7X Rate
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NCBIWA 2007
Charleston Battery
Urban Centers Will Armor Shoreline Just As They
Have For Centuries. (Until When?)
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Beach Response To SLR
Application of Bruun (1962) Rule
By Hands 1981
Pawleys Is Post HUGO
yrX/Z(RA)
Equilibrium Profile Volumes Allow Projection Of
Shoreline Displacement Under SLR
Kana 1993
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NCBIWA 2007
Barrier Island Formation Theories Submergence
As Sea Level Rises
In-place Drowning Of Coastal Ridges
Early Proponent W J McGee (1890)
Other Advocates J H Hoyt (1967) - Based on
Georgia Studies!
Diagram Based on Hoyt, 1967 - Fig 5.
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NCBIWA 2007
Barrier Island Movement
Sediment Supply vs SLR
gt Accretion
ltErosion - Washover
Stable
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NCBIWA 2007

• Baseline SLR _at_ 0.8 ft
• Scattered losses of 1st Row Homes
• Inlet Bypassing Continues Natural Replenishment
  of Beaches
• Low Scenario SLR _at_ 2.9 ft
• -Begin to lose some 2nd Row Homes
• -220 to 400 ft of Shoreline Retreat
• -Causeways Flooded Regularly

Results for Sullivans Island
Isle of Palms
Sullivans Island
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NCBIWA 2007
Many Causeways To Coastal Property Are lt 2 ft
above Peak Yearly Tide Levels
Hey Joe, Do you Know a short cut I can take to
work instead of the causeway?
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Sea Level Controls On Wetlands Zonation
To Assess Potential Impacts to Tidal Wetlands
Need Site-Specific Elevation Ranges
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NCBIWA 2007
Principal Inter-tidal Habitat Controls -Tidal
Flooding Frequency -Substrate Elevation
Salt Marsh
Sheltered Mud Flats
Open Water - Oyster Mounds Mud Flats Marsh
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Case Studies Charleston and New Jersey
NJ case more applicable to NCs tide range!
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NCBIWA 2007
Different Tide Ranges Similar Species Zonation!
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NCBIWA 2007
Yellow is Low Marsh Spartina alterniflora!
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NCBIWA 2007
Maintaining Marshes Will Depend On Available Land
Area That is _at_ MHW SLR
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SLR Impacts That Will Matter To Most People
More Private Shore Protection Structures At Edge
Of Marsh That Individuals Have To Pay For
Themselves
More Frequent Inconveniences!
More Causeways Lost
More Commuting Delays - Waiting On Normal Tides!
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Action Needed But When?
Q. How Often Are You Willing to Wait For A Peak
Flood Tide To Get Off The Causeway Before You Get
Home From Work?

• Once per year is no big deal.
• Once per month, and Ill just Buy A Hummer.
• Once per week, And Ill call my Congressman to
  Fix The problem.
• Once per day and Ill demand the government buy
  my property.
• Are there any other choices?

Were still at A in Most Places!