South Florida Sea Level Rise Projections and Flood Risk Concerns

Transcription

1 South Florida Sea Level Rise Projections and Flood Risk Concerns MIAMI MIAMI Biscayne Bay Glenn B. Landers, P.E. Planning and Policy Division Jacksonville District EVERGLADES NATIONAL PARK USACE Flood Risk Management and Silver Jackets Workshop August 16, 2011 Nashville, TN Florida Bay

2 Presentation Outline Geologic Info on Sea Level Change through Time SLR Projections for South Florida SLR Concerns and Examples for Everglades Restoration and South Florida Flood Risk Management Next Steps

3 Florida Through Time Sea Level Change Happens! 120,000 years ago 18,000 years ago Today + 6 meters (20 )* meters (420 ) *~ ½ from Greenland *~ ½ from Antarctica Credit: Dr. Harold R. Wanless; University of Miami, Department of Geological Sciences; co-chair of Miami-Dade Climate Change Task Force

4 Rate of SLR (mm/yr) Sea-level rise rates since the Last Glacial Maximum mwp-ia 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) Thousands of 14 C years before present (Slide courtesy of Rob Thieler, USGS) (SLR rate based on Fairbanks, 1989)

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

6 United Kingdom Climate Adaptation Approaches: Precautionary versus managed adaptive Figure courtesy of Jonathan Simm, HR Wallingford, UK

7 NOAA Tide Stations in Florida Key West has the longest non-continuous U.S. tide station record with 130+ years. Per EC , a Compliant Tide Station is a station currently being monitored and having at least 40 years of continuous prior record. Compliant Tide Stations in Florida are: Key West, Vaca Key, Naples, St. Petersburg, Cedar Key, Apalachicola, Pensacola, Mayport and Fernandina Beach. There are also other currently monitored NOAA tide stations in Florida with less than 40 year or non-continuous records. Most of Florida is very stable geologically, so sea level change is similar around the state.

8 Relative Rise (feet) Relative Rise (meters) Planning Scenarios for Sea Level Change Impacts Assessment and Adaptation Studies in Florida U.S. Army Corps of Engineers EC Relative Sea Level Rise Projections 100 year 50 year 20 year United Nations Climate Change Science Compendium, m to 2.0 meters (2.62 to 6.56 feet) by 2100 Key West, Vaca Key, Mayport, St. Petersburg Apalachicola Year

9 Relative Rise (feet) Relative Sea Level Rise Scenarios for South Florida Notes: Projections are for historic, modified NRC Curve I and modified NRC Curve III rates of sea level change developed for South Florida per USACE Engineering Circular (EC) This EC is based on guidance in the National Research Council (NRC) report, Responding to Changes in Sea Level; Engineering Implications dated September, The projection is developed using the historic rate of sea level rise at Key West as reported by NOAA (2.24 mm/yr). The dashed line indicates that the EC equation is being used past the year The underlying documents supporting the EC do not address dates beyond yr Planning Horizon Year Elapsed Time, years Relative Sea Level Rise, inches Historic Modified NRC Curve I Modified NRC Curve III yr Planning yr Horizon Year

10 Sea Level Rise (FT) 90% of County below 10 ft MSL Cumulative Percent of Brevard and Miami-Dade Counties Impacted versus Sea Level Rise Elevations Credit: Peter W. Harlem, Florida International University, Southeast Environmental Research Center

11 Sea Level Rise in South Florida A little less than 1 foot during the past century measured at Key West A 2 foot rise would have significant effects

12 Sea Level Rise in South Florida A little less than 1 foot during the past century measured at Key West A 4-5 foot rise would have dramatic impacts MHHW +120 cm (4 ft) rise MHHW +150 cm (5 ft) rise

13 CERP Drainage Patterns Historic Flow Current Flow Future Flow (USACE, 2010)

14 Everglades Restoration Restore natural hydrologic conditions in the remaining 50% of historic Everglades Water quantity, quality, timing and distribution Maintain or enhance existing services in developed areas Flood Risk Reduction, Water Supply, and other for +/- 6.5 M people Use Adaptive Management to adjust over time Sustain ecosystem benefits for future generations Opportunities to develop Project and Watershed (sub-regional) Adaptation Strategies

15 SLR Impacts on CERP areas Ocean Avenue, A1A Direct Impacts (storm surge) Flood Protection (urban flooding) Water Supply (saltwater intrusion) Natural System (coastal ecosystems) (SFWMD, 2011) 2008) (FAU,

16 SLR Impacts NATURAL SYSTEM Southern Everglades Natural System Relocation and possible reduction of mangrove forests Forced migration of wading birds northward Potential peat collapse, coastal erosion, and redistribution of sediments Salinity intrusion into freshwater marshes can: discharge toxic hydrogen sulfide, cause coastal fish kills, and increase habitat loss (SFWMD, 2011)

17 SLR Impacts DIRECT IMPACTS INUNDATION OF BARRIER ISLANDS AND COASTAL INFRASTRUCTURE COASTAL FLOODING & ECOSYSTEM CHANGES BEACH EROSION (FAU, 2008) (SAHA, FIU, 2011)

18 FLOOD DAMAGE REDUCTION reduced discharge from coastal structures SLR Impacts (Heimlich, FAU, 2009) (SFWMD, 2011)

19 Flood Damage Concerns Sea level rise will reduce effectiveness of gravity drainage canals and increase flood frequency The population of South Florida is 6.5 million and growing

20 Flood Damage Concerns FLOW Sea level rise will reduce effectiveness of gravity drainage canals The population of South Florida is 6.5 million and growing

21 Flood Risk vs Water Supply Concerns Conceptual diagram of hydrologic system of south Florida (Langevin, USGS, 2000) Shallow wells are the primary source of drinking water in South Florida communities Continued sea level rise will cause saltwater intrusion into wells and create a need for new freshwater sources --- OR --- Protecting water supply wells with higher canal stages will increase flooding in many low elevation communities

22 Climate Change Concerns for South Florida Sea Level Rise Salinity changes in coastal bays Shoreline retreat with natural habitat changes/losses Increasing flooding in coastal areas Saltwater intrusion in water supply wells, OR higher canal stages and flood risks Uncertainties and risks in rate and depth of sea level rise Warmer Temperatures Evaporation losses up; water supply down Stresses on plant, animal, and marine ecosystems Changes in growing season and migratory patterns Changes in water quality Hydrologic Pattern Changes Potential for less frequent and more intense rain events Potential increased tropical storm intensity or frequency

23 Scenarios for Sea-Level Rise U.N. Climate Change Science Compendium to 2.0 meters (2.62 to 6.56 feet) by 2100 Use GIS to develop flooded area maps in +1ft increments to +6ft of SLC

24 Biscayne Bay Coastal Wetlands Project Area Miami Close-up Area In Next Slides Turkey Point Nuclear Power Plant And Cooling Pond Mean High High Water

25 Biscayne Bay Coastal Wetlands Southern Portion A A Mean High High Water

26 Biscayne Bay Coastal Wetlands Project Section A-A Conceptual Drawing Not to Scale A A Spreader Canal South of S-711 L-31 E MSL + 2 feet MSL + 1 foot Riser Culvert Flap Gate MSL 3 Depth Required For Fish Nursery

27 Mean High High Water Plus 0.5 ft

28 Mean High High Water Plus 1.0 ft

29 Mean High High Water Plus 1.5 ft

30 Mean High High Water Plus 2.0 ft

31 Coastal Flood Risk Frequency Future changes in coastal flood risks depend on: Amount and rate of relative sea level rise Storm tide elevation and frequency Flood threshold or stage elevation at which damages occur Rising relative sea level will allow future storm tides to: Reach higher elevations than past storms Exceed flood stage more frequently than past storms Future storm damages will occur to geographic areas not previously impacted by elevated sea levels Credit: Dr. David L. Kriebel, PE, U.S. Naval Academy,

32 Visual of Existing Sea Level Rise Trends Scale in millimeters per year does not convey a threat from sea level rise Credit: Dr. David L. Kriebel, PE, U.S. Naval Academy, kriebel@usna.edu

33 Visual of Future Sea Level Scenarios Does not convey much threat to infrastructure higher than about 1 m or 1.5 m above current sea level Credit: Dr. David L. Kriebel, PE, U.S. Naval Academy, kriebel@usna.edu

34 Display SLR plus Storm Effects Combine past tidal fluctuations with future SLR trends Dr. Chip Fletcher and students at Univ of Hawaii Step 1: De-trend tide gage records Step 2: Develop future SLR trends Credit: Dr. David L. Kriebel, PE, U.S. Naval Academy,

35 Tide Level above STND (ft) One Interpretation of Results Average Frequency of Flooding Flood once every 10 years Flood threshold for USNA Engineering Building Flood once every 5 years Annapolis, MD Flood once per year Flood every other month or 6 months per year Flood every month or 12 times per year Previous MSL Trend 1 month 2 month 9 1 yr 8 5 yr MSL reaches building 10 yr 50 yr Diurnal Range Years from present Credit: Dr. David L. Kriebel, PE, U.S. Naval Academy, kriebel@usna.edu

36 Next Steps USACE Sea Level Change Guidance should address storm events as agents that cause damage in an era of rising sea level Storm tides, not mean sea level itself, are responsible for flooding and structural loading Analyze historical storm tides relative to past sea level trends Fit probability curves to de-trended past storm tides Couple past storm probabilities with future SLC scenarios Subject to limiting assumptions about storm climatology Compare future storm tide probabilities to coastal flood stage to define probability of flooding Flood stage = MHHW + 3 ft (+2 in Gulf?) Results are sensitive to flood stage USACE projects may require analysis with actual elevations in each reach Credit: Dr. David L. Kriebel, PE, U.S. Naval Academy, kriebel@usna.edu

37 South Florida Sea Level Rise Flood Risk Concerns Key Take Away Points USACE SLR projections are based on guidance from the National Research Council, are site specific and include local uplift or subsidence. Does not address wave and storm surge frequency. Sea level rise is a multi-generational upward TREND producing PERMANENT increases in flood risk frequency Leading Indicators of Sea Level Rise, such as the reduction in polar ice caps, and the recent rapid increases in the rate of glacier melting worldwide forecast significant SLR rate increases Long Term Sea Level Rise Adaptation Strategies are needed at project, community, watershed, and national scales SE FL Climate Compact 4 counties, Key West to Palm Beach, use USACE SLR 50 yr projections for adaptation planning

38 Thank you! For additional information, contact: