Jason M. Evans, PhD Environmental Policy Program

Carl Vinson Institute of Government

http://www2.wsav.com/mgmedia/image/294/0/26340/viewer_sends_photos_of_tybee_flooding/

http://3.bp.blogspot.com/_UZCeUDMh1X4/SxV0euA9iAI/AAAAAAAADak/9kl5bAkCgdk/s400/Tybee+Roads.jpg

October 28, 2013 Local Government Challenges in Dealing with Rising Seas

Yulee, FL

Most densely developed barrier island in Georgia

~3000 year round residents

~2000 seasonal residents

Popular tourist beach for Savannah area

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1935 1945 1955 1965 1975 1985 1995 2005

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Sea level rise at Ft. Pulaski

1935 - 2010

Data source: Natural Environment Research Council Data authority: National Oceanographic and Atmospheric Administration http://www.psmsl.org/data/obtaining/stations/395.php

Local trend of approximately 1 foot rise over 100 years

Primary funding

• NOAA Sea Grant Community Climate Adaptation Initiative (February 2012 – January 2014)

Partners

• City of Tybee Island

• Georgia Sea Grant (PI – Chuck Hopkinson)

• Carl Vinson Institute of Government • Lead facilitation and GIS-based benefit/cost modeling

• UGA College of Environment and Design

• UGA Marine Extension Services

• Catalysis Adaptation Partners • Facilitation support and technical support for adaptation costing

• Georgia DNR Coastal Resources Division

• Chatham-Savannah Metropolitan Planning Commission

http://www.swedishwaterhouse.se/galleries/images/blog2012/Ven-Diagram.jpg?__scale=c:transparent,t:4,r=0,q=70,w:396,h:252

Virtue Pragmatism

Current sea level 1 foot rise

Current sea level 3 feet rise

US80 to Tybee Island

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Infrastructure Design life Sea level rise range

Municipal water distribution

30 – 60 years 0.4 – 2.7 feet

Wastewater and stormwater pipes

30 – 60 years 0.4 – 2.7 feet

Sewage treatment facilities

~ 50 years 0.5 – 2.3 feet

Bridges 75 years or more 0.75 – 4.0 feet

Right of ways (highways and utilities)

100+ years 1.0 – 6.0 feet

Adapted from Deyle 2009

Front island beach erosion ◦ Loss of tourism

◦ Decreased storm surge buffer

Flooding of US80 ◦ Decreased tourism access

◦ Increased potential for stranding in emergency situations

Back island erosion and tidal flooding ◦ Increased flooding of marsh front yards and homes

◦ Stormwater drainage problems in SW island at high tides

Protect, or “Stand and Defend” ◦ Sea walls, levees, storm surge gates

Accommodate, or “Buy Some Time” ◦ Beach renourishments, elevate infrastructure

Avoid, or “Stay Out of the Way” ◦ Zoning setbacks, build outside of hazard zones

Retreat, or “Get Out of the Way ◦ Rolling easements, buy outs, abandon unusable

infrastructure Adapted from Deyle 2009

Sea walls and levees ◦ Very expensive to

permit and construct

◦ Maintenance expenses will increase over time

◦ Radically alter beach and marsh dynamics

http://sav-cdn.com/sites/default/files/imagecache/superphoto/6792890.jpg

http://www.wired.com/images/article/magazine/1701/ff_dutch_delta_levees_f.jpg

Dutch example

Beach renourishment ◦ Expense, scaling,

potential environmental concerns

Elevate infrastructure

◦ Expense, scaling, potential environmental concerns

US 80 (May 6, 2012, 9:50pm) http://coastalnewstoday.com/wp-content/uploads/2011/11/Tybee-Island-Renourishment-Plan.jpg

http://climatetechwiki.org/sites/climatetechwiki.org/files/images/teaser/media%20image%201.jpg

Zoning setbacks to avoid future hazards ◦ Uncertainty in sea

level rise projections create difficulties for long range planning

◦ Creates conflicts with vested property rights

Rolling easements as sea encroaches

No rebuild in high hazard zone after disaster strikes

Adapted from Deyle 2009

Hurricane Opal, Florida panhandle 1995 Deyle 2009

Decision 1: What rate of sea level rise does the City want to plan for?

Plan for rate of 2060 sea level rise equivalent to

2.3 feet (High)

1.3 feet (Intermediate)

We also included linear trend sea level rise:

0.6 feet (Low)

Raise water well facilities above 100 year flood height

Raise US80 to 3 feet above current grade

Continue renourishing beaches to keep up with sea level rise

Upgrade drainage infrastructure in southwest island

Build 4 foot sea wall over current MHHW in southwest island

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Benefit/Cost Results for

Adaptation Actions

Image Source: NOAA Sea Level Rise Viewer http://www.csc.noaa.gov/slr/viewer/#

3 feet sea level rise

Predicted tidal flood extent with 9.6 ft MLLW tide (Ft. Pulaski reference)

Approximate annual

“king tide flood” currently

Inundation model

Predicted tidal flood extent with 10.1 ft MLLW tide (Ft. Pulaski reference)

Annual “king tide flood” at 6 inches sea level rise

Inundation Model

Assessed structures in Tybee Island City Limits (excluding docks)

King tide flood with 6 inches sea level rise

Pipe Flow Model

(Based on Georgia Coastal LiDAR Elevation DEM at 3ft cell size)

November 14-15, 2012

Constructed 2011, ~$450,000

King tide flood 6 inches sea level rise

Tide Gate Model

(Based on Georgia Coastal LiDAR Elevation DEM at 3ft cell size)

Sea Level Rise by 2060 Avoided building

damages and economic

activity loss

(Net Present Value)

Approximate year that

annual bank overflow

begins (~0.75 feet of sea

level rise)

Linear Trend (0.6 feet) $2,100,000 2060 - 2070

Intermediate (1.3 feet) $3,500,000 2040 - 2050

High (2.3 feet) $3,300,000 2030 - 2035

All values from saltwater flooding of buildings only With additional benefits from freshwater flood mitigation and avoided losses to salt intolerant landscaping, likely a close to “no regrets” action under any scenario

Estimated ~4600 feet of engineered sea wall at 4 feet above MHHW

Sea Level Rise Avoided property damages

and economic activity loss

through 2060

(Net Present Value)

~Year that annual bank

overflow begins (0.75 feet

of sea level rise)

Linear Trend (0.66 feet) $1,300,000 2067

Intermediate (1.3 feet) $1,100,000 2042

High (2.3 feet) $840,000 2033

Sea Level Rise Avoided structure

damage and

economic activity

loss through 2060

from sea wall

(Net Present Value)

Estimated cost *

($3500 /linear foot

and 2.5% annual

maintenance)

Benefit:Cost Ratio

Linear Trend

(0.6 ft)

$510,000 $25,000,000 0.02

Intermediate

(1.3 ft)

$6,500,000 $25,000,000 0.26

High

(2.3 ft)

$26,000,000 $25,000,000 1.04

*Permitting and potential mitigation costs not directly factored

Local “patch up” of existing private bulkheads may provide similar benefits for at least two decades

King tide at 1 foot of sea level rise

Argument for “duct tape” adaptation?

Total Annual Property Flood Loss = $5.1 million (Present Values)

Total Annual Property Flood Loss = $4.9 million (Present Values)

February 28 sea level rise workshop in St. Marys:

125 attendees – including several elected and appointed local officials from Brunswick and St. Marys

Successful application for Community Climate Adaptation Initiative 2013

Benefit-cost method can be adapted for more complex land use change and zoning scenarios