Striking A Balance: Implications of Shoreline Change Along the South Carolina Coast The Physical Environment

Transcription

1 Striking A Balance: Implications of Shoreline Change Along the South Carolina Coast The Physical Environment Paul T. Gayes Burroughs and Chapin Center for Marine and Wetland Studies Coastal Carolina University South Carolina s Changing Shoreline: Implications for the Future Workshop - Wednesday, November

2 The Issues Coney Island, New York 1941 Reprinted From Coastal Erosion Manual USACE (2006) after Time Magazine August 10, 1987; Time Inc. Demographic Shift to the Shore Landward Migrating Shoreline

3 Rising Seas and landwards shift of the shoreline into An increasingly Massive but static infrastructure The beach, an important public resources, is compressed between the two colliding trends Coastal Infrastructure and Economies at risk Garden City Beach, 2001 Myrtle Beach, 2005

4 Sediment Supply Responds to Drivers Drivers of Shoreline Change Coastal Responses Implications Waves Currents Agents of Change Coastal Systems Are Tied to Sea Level and Associated Change Sea Level Defines Location of the Conflict 1.3 feet / century

5 Landscape Change Waties Island BEACH FILL Garden City Photo by Tabby Shelton MB Pavilion Area 1929 Curt Teich Postcard

6 Long Term vs. Short Term Chronic / Episodic / Cyclic Global / Regional / Local Sea Level is the large long term driver Sea level indictors Fossil beaches / marshes Avg Ice Extent ~400 feet Jez o Hare - Source NASA.gov Fairbanks, 1989 Nature

7 Sea Level Rise - Landward Shift in Environments Tied to Sea Level Beaches, Inlets, Marshes, Estuaries, Wetlands Tree Stumps and fragments Within old flood plain of Pee Dee River 15 miles of modern Murrells Inlet Radiocarbon age 12,000 years From Barnhardt et al, 2008, Coastal Change Along the Shore of Northeastern South Carolina: The South Carolina Coastal Erosion Study; U.S. Geological Survey Circular 1339.

8 SEA LEVEL CHANGE Century to Millennial Trends/Variability Compiled by Horton et al., 2009 New work funded by SC Sea Grant Gayes, van de Plassche and Springer Murrells Inlet and Winyah Bay

9 1 Foot Decadal Trends/Variability Annual Trends/Variability 1.3 feet / century At Myrtle Beach Springmaid Pier Tide Gauge Average Annual Variability Present Springmaid Pier Tide Gauge Physical Measurement of Sea Level Myrtle Beach Present

10 EPISODIC Hurricane Storm Surge Level Open Water CAT 1 USACE Projections for Horry and Georgetown County CAT 2 CAT 3 CAT 4 CAT Yr FLood

11 Maximum Storm Surge in Katrina ~ 31 feet Hurricane Hugo This Building is 43 feet above sea level Surfside Beach Chandeleur Islands Folly Beach Source USGS.gov

12 CYCLIC- Inlet By-Passing SC CORM Classifies and Manages as Inlet Hazard Zones Courtesy of Chris Mack- Dewberry Engineering

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14 Coastal Response Constantly Adjusting Large Long Term Sea Level Change Annual/Seasonal Fair-Foul Weather

15 Nourishment Coastal Erosion River Input ~ 0 SEDIMENT BUDGET Grand Strands Largest Natural Source of Sediment is from Erosion Erosion Rates feet/year Loss Alongshore Loss to Tidal Deltas Loss Offshore

16 PROTECT STRUCTURES Seawalls Sand Bags Garden City Beach Pre-1998 Nourishment Sullivans Island 2008 Groins RESTRICT LONG SHORE TRANSPORT Isle of Palms Sand Bags Groins Garden City Lengthen time to renourish DEFEND?

17 Debordieu Hunting Island DEFEND SOME AREAS / RETREAT IN OTHERS?

18 Hunting Island Retreat?

19 IMPLICATIONS South Carolina Primary Defense from Sediment Budget Deficit Beach Nourishment Costs Some Win / Some Lose Sand Borrow Sources Environmental Use Conflict 2005 Folly Beach Renourishment

20 South Carolina Beach Nourishment Area Year Length Cost Sand Volume (miles) (cubic yards) Seabrook Island $1,500, ,000 Debidue Beach $1,000, ,000 Hilton Head Island $10,000,000 2,000,000 Hunting Island $2,900, ,000 Folly Beach $15,000,000 2,500,000 Edisto Beach $1,500, ,000 Grand Strand $54,000,000 5,000,000 Hilton Head Island $11,000,000 2,000,000 Sullivans Island $200,000 35,000 Debidue Beach $1,500, ,000 Pawleys Island $1,200, ,000 Daufuskie Island $6,000,000 1,400,000 Sea Pines-HHI $1,200, ,000 Folly Beach $12,500,000 2,300,000 Debidue Beach $5,600, ,000 Edisto Beach $8,000, ,000 Hunting Island $4,300, ,000 Hilton Head Island $19,000,000 2,700,000 Folly Beach $7,500, ,000 Grand Strand $40,700,000 2,900,000 Isle of Palms $9,900, ,00 21 Projects $194,150,000 27,700,000

21 Sediment Starved Inner Shelf Critical Habitat

22 Sand Resources v. Area of Demand Transportation Costs Costs will Increase Unintended consequences Federal v. State Resources Conflict with Other Uses Wind Farms, Ocean Disposal etc.

23 Scale and Periodicity Function of Storm patterns Sea Level Economics Planning Design Construction Maintain Natural Losses Storm Events $$$ Financial Storms

24 International Panel on Climate Change Projections of Future Sea Level No Change from Present Rate

25 Recent North Carolina Tracing of Marsh Rise Similar work repeated along US East Coast Shows Similar Trends Presently Refining Murrells Inlet and Hilton Head Sea level Records From Kemp et al., 2009

26 Garden City Beach

27 Flooding in the usual places at the time of High Tide Sea Levels Rose Two Feet This Summer in U.S. East Brian Handwerk for National Geographic News September 10, 2009 Sea levels rose as much as 2 feet (60 centimeters) higher than predicted this summer along the U.S. East Coast, surprising scientists who forecast such periodic fluctuations. June 23, 2009 Photos from Atlantic Avenue in Garden City June 23, 2009

28 IMPLICATIONS Sea Ranch Hotel Kill Devil Hills NC Most Recent Nov 12 th Nor easter NC Spent > $98 Million Maintaining Repairing Road IGCP Conference Hoisted at CCU

29 CONCLUSIONS SEA LEVEL IS RISING Directly Measured Over Last Years and longer term Pressure on Beaches, Drainage Systems, Groundwater, Wetlands There are many reasons to expect an acceleration in future is real STORMS HAPPEN Waves/Currents/Winds/Rainfall/Temperature over time is CLIMATE Climate and Weather Change We may Influence but won t stop it. This summers slight shift in pressure and winds resulted in an anomalous 1-2 foot higher than normal sea level along the entire east coast COASTAL ROADS and LOW LYING COMMUNITIES IN SC DID FLOOD ABSENT A SIGNIFICANT STORM SEA LEVEL & STORMS CHALLENGE US DIFFERENTLY Renourishment Doesn t Increase Elevation of Property Hugo was NOT the Big One in the Grand Strand or Charleston We Will Not Fair Well In A Katrina While Risk Is Small Any Given Year There Is A BAD Day Somewhere Out There That We As Not Prepared For

30 SOCIETY CAN ENGINEER SOLUTIONS TO MAINTAIN STATUS QUO New Orleans Was Not Initially Settled Below Sea Level The Scale Of Protection At New Orleans Clearly Insufficient It Is Unlikely We Will : 1) Be Able To Afford Them For All / Many Areas 2) Find Resulting Environmental Changes Acceptable SOCIETY MUST ACTIVELY WORKS AGAINST THE NATURAL SYSTEM MAINTAIN / STOP CHANGE Nature Is: More Persistent Than We Are Doesn t Need Bond Issues Or Tax Revenue And Has Better Credit Doesn t Need Votes and Consensus to Act Chooses The Time/Location Of Battles = Is the Home Team UNDERSTANDING AND MANAGEMENT OF COASTAL SYSTEMS SHIFTING TO REGIONAL PERSPECTIVE Waves And Sediment Don t Care Where Jurisdictional Boundaries Are

31 Whatever Policy / Action Taken Today will Likely look Successful Tomorrow What Is or Is Not Implemented Today Will Be Tested in the Future Some Areas Will Arrive At the Future Sooner Than Others (NO, Hunting Island etc.) A Great Deal Of Focus Presently on Federal/ State and Local Levels- There is Need For Information, Data and Objective Analysis to Provide Best Guidance