Sea Level Rise and Climate Change Impacts on Stormwater Management Facilities in South Florida

1. Sea Level Rise and Climate Change Impacts on Stormwater Management Facilities in South Florida Frank E. Marshall, PhD PE Frank Marshall Engineering, PL New Smyrna Beach, FL Southeast Florida Regional Climate Change Compact RCAP Stormwater Workshop January 22, 2015

2. What is Sea Level Rise (SLR)? • SLR is an increasing trend in the average elevation of the surface of the world’s oceans • The two main mechanisms are: • thermal expansion of ocean water (no additional water mass) • melting of major stores of land ice like glaciers and ice sheets (additional water mass) • SLR is one of several lines of evidence supporting the hypothesis that the global climate has recently warmed

3. From IPCC 2013 From: Global Sea Level Rise Scenarios for the United States National Climate Assessment, NOAA Technical Report OAR CPO-1, 2012 Three Global SLR Estimates

4. Local SLR ProjectionsFrom Southeast Florida Regional Climate Change Compact

5. What is Climate Change? • A significant and lasting change in the average and range of weather conditions over the last 50-100 years • First recorded usage of term is fairly recent, 1980-85 • Primarily related to an increase in the average atmospheric temperature - 2014 warmest on record • Includes changes in global or regional climate patterns, particular rainfall and evaporation • A subject that has largely been ignored by politicians, except in South Florida

6. Expected Changes to Sea Level and Climate in South Florida by 2050 from SFWMD (2011) and Regional Climate Change Compact (2011) • SLR: 6-17 inches higher • Temperature – increase of 1 – 2 degrees C • Rainfall - +/- 5%, -3 to +2 inches • more heavy precipitation • increase in frequency and duration of dry spells • Evaporation / transpiration – 3 – 6 inches • higher uncertainty in evaporation changes • Tropical Storms – fewer but more powerful storms

7. Why is Southeast Florida So Vulnerable to SLR and Climate Change? • Long shoreline = high exposure to SLR effects • Relatively low elevation of landscape • The largest number of people, dwellings, and infrastructure in the coastal region of US • Presence of regional water management system that provides conduit for inland connectivity • High groundwater levels and porous substrate • Numerous drainage wells

8. What are Potential Impacts of SLR and CC to Stormwater Management Facility Functions? • Increase in groundwater levels will reduce efficiency of French drains/ exfiltration trenches • Reduction of infiltration and soil storage capacity • Increased runoff • Reduction of discharge capacity of outfalls • Drainage wells that become artesian • Brackish water entering system from seawall overtopping

9. Recommendations for Stormwater Management Related to SLR and CC • Sustainability Planning: SP-2, SP-3, SP-4, SP-5, SP-6, SP-7, SP-10, SP-12 • Water Supply: WS-4, WS-12, WS-17 • Regional Resilience RR-1, RR-6, RR-7 • Public Outreach: PO-6, PO-10 • Public Policy: PP-1 • 17 recommendations out of 110 total

10. How Do You Assess Stormwater Management Infrastructure Vulnerability? • Perform a vulnerability analysis - See Dr. Nancy Gassman presentation (following) • Prepare or upgrade stormwater master plan – use stormwater utility funding • The areas affected by SLR will primarily be: • areas adjacent to the coast • areas affected by storm surge • areas with elevations less than ~12ft NGVD29 or ~10ft NAVD88 • areas with drainage wells • areas with French drains or exfiltration trenches • areas with direct connection to C&SF Project • Assessment must include hydrologic drivers affected by climate change • rainfall • evaporation • occurrence and strength of tropical storm activity and extreme events

11. Example of SLR / CC Assessment Approach • Step 1 – Characterize site or region using field data, existing maps, topography (LIDAR), aerial maps/Google Earth, and infrastructure inventories • Step 2 – Identify potentially vulnerable areas • Step 3, two parts – assemble data: • For SLR, use local tide, Key West, or other long-term tide data; use regression models as-needed; include appropriate increases and storm surge estimates • For climate change use: • existing hydrologic data (weather records) with appropriate increases/decreases • tropical storm data, including storm surge • climate indices • Step 4 – Evaluate and analyze the accumulated information • Step 5 -Formulate an appropriate engineering response • Step 6 – Present the results in stormwater master plan and to decision-makers

12. Assessment Matrix from Florida Bay SLR / Climate Change Assessment SLR Effects From Marshall, Cosby, and Nuttle (2014) for Everglades national Park Climate Change Effects

13. How Should Results be Presented?Stop Light Format is Proven Method to Get Message Across to Decision-makers From Marshall, Banks, and Cook. 2014. Ecological Indicators 44 (2014) 81–91

14. Stormwater Management OpportunitiesLocal Example: City of Delray Beach Marina Historic District ‘King’ high tide Nov 2014 • Sustainability Officer and SLR Task Force on-board • In early phases of getting a handle on vulnerability • On the highest tides flooding already occurs in lowest areas • Areas with a direct connection to the ocean or ICW • Areas adjacent to ICW where overtopping of seawall can occur – ex: Marine Way • Opportunities for adaptation: Atlantic Crossing – large private redevelopment project - opportunity for private/public partnership in an area susceptible to flooding - excellent opportunity to use LIDS (see talks this afternoon) Veterans Park – Excellent opportunity to promote demonstration of climate-change resistant stormwater management practices Marina Historic District – street floods frequently, narrow R/W, low elevations, City/resident cooperation is needed

15. Local Example: City of Ft LauderdaleSLR / Climate Change Initiatives • Significant issues: • Low elevation areas • Areas influenced by tide • Private seawalls below Building Code elevation • Water coming from western areas outside of City • Additional impervious areas being added to existing development • Hard to address water quality issues associated with pumping • Solutions: installing/constructing bio-swales and flap valves on City facilities, upgrading design storm for new development (requires more on-site storage) • City-wide model of stormwater systems being developed • Opportunity: River Oaks Preserve – 13 acres, natural vegetation, water storage and water quality benefits

16. Local Example: Village of Wellington • Demonstration project by Streamline Technologies, Inc. • Wellington is west of Atlantic Coastal ridge • Drainage actively pumped into C-51 regional system canal • Initial modeling objectives • 100-Year Flood Levels • Levee Breach Analysis • Additional SLR/CC analysis investigated increased GWT • ICPR-4: engineering model • groundwater layer • 1-d and 2-d surface features • Sea Level Rise is incorporated into boundary conditions • Climate change is incorporated into precipitation and ET • Model can be applied throughout 4-county area Model Extents Pumped Drainage to C-51 WCA 1 Simulated Levee Breach Location

17. Initial GWT: 12’ NGVD29 Initial GWT: 13’ NGVD29 Simulation Hour 56 Impact: Inundation Occurs Several Hours Sooner with a Higher Initial Water Table

18. Local Example: Miami Beach • Bad press forced action – South Beach, for example • Existing drainage wells go artesian on highest tides • Insurance companies are concerned about flooding • Primary level of service – maintain property values • A number of large pump stations already installed • 2 South Beach pump stations were brought on-line for 2014 ‘King’ tide – successful operation • 50-70 pump stations ultimately • Price tag on order of $300 million + • FDOT also involved • See Bruce Mowry presentation in afternoon

19. Final Thought for Stormwater Infrastructure Assessments in South Florida Be aware of elevation datum – NGVD29 or NAVD88? • There is 1.2 – 1.5 ft difference on east coast of Florida • Older survey and inventory data are NGVD29 • More recent information is NAVD88 • Very, very important

20. Summary and Conclusions • Sea level rise (SLR) and climate change are occurring and on the radar screen in South Florida • SLR ~ 9 – 24 inches by 2060 • Temperature – increase of 1 – 2 degrees C • Rainfall - +/- 5%, -3 to +2 inches • more heavy precipitation • increase in frequency and duration of dry spells • Evaporation / transpiration – 3 – 6 inches • higher uncertainty in evaporation changes • Tropical Storms – Higher potential for strong storm development; fewer but more powerful storms

21. Summary and Conclusions • South Florida stormwater infrastructure is highly vulnerable to the effects of SLR and climate change • The 4-County Compact: effectively assisting communities in assessing the effects of SLR and CC on stormwater infrastructure • A stormwater system vulnerability assessment should be a part of the sustainability program for all South Florida governments • How to implement? Upgrade/update stormwater master plans • Have I mentioned datum?

22. Thank You! Frank Marshall Engineering, PL New Smyrna Beach, FL 386.451.9381 clfinc@earthlink.net