Impacts of restoration strategies on growing flood hazards, and unknowns

Transcription

1 Impacts of restoration strategies on growing flood hazards, and unknowns Philip Orton Research Assistant Professor Davidson Laboratory, Stevens Institute of Technology Funding: NOAA s RISA Program (Rosenzweig PI) Consortium for Climate Risk in the Urban Northeast Philip Orton, Stevens Institute 1 Hudson River Foundation, NYSERDA, NOAA Coastal Ocean Climate Applications (COCA)

2 Outline How have NYC coastal flood hazards changed? What is our best current estimate of flooding at various return periods? How can estuary restoration affect flood hazards? can reduce waves can reduce flood height can improve multiple layers of resilience to hazard What are the primary unknowns? Philip Orton, Stevens Institute 2

3 Historically Growing Storm Tides Talke, Orton, Jay Geophysical Research Letters 2014 Possible reasons: Climate variability (emergence from Little Ice Age) Climate change Human changes made to the harbor (e.g. elimination of wetlands, dredging channels) Annual Maximum Storm Tide (above MSL) from gauges around the New York Harbor area (map at left) 3

4 Rising 5-year and 10-year Storm Tides and Flood Elevations (with SLR) Possible reasons: Climate variability (emergence from Little Ice Age) Climate change Human changes made to the harbor (e.g. elimination of wetlands, dredging channels) 4

5 2.68 m 3.50 m 2.03 m 2.46 m FEMA 2008 Lin et al FEMA 2013 NOAA 2014; Sweet et al What is our best current estimate of flooding at various return periods? 4-year flood (25%/year): 1.75 m MSL 10-year flood (10%/year): 2.0 m MSL 100-year flood highly uncertain, perhaps even evolving studies suggest from m Philip Orton, Stevens Institute 5

6 NYC is not The Netherlands Different Hazard Profile There is no such thing as total coastal protection at NYC Focus less on vertical barriers Focus more on elevating systems Focus more on using antifragile systems that bend but don t catastrophically fail POTENTIAL RISK = 11.7 ft 6

7 How can estuary restoration affect flood hazards? Wetlands, oysters, shallowing Reversing dredging shipping channel depths Restoring wetlands and islands (below) Growing oyster reefs for breaking waves Elders East Island, Jamaica Bay, NYC, 2006 Elders East Island, Jamaica Bay, NYC, 2010 Photo credits: US Army Corps of Engineers 7

8 Collaborative coastal adaptation (Chapter 3) work done with: Hugh Roberts, Zach Cobell, at Arcadis, Inc. Scape Landscape Architecture Parsons-Brinckerhoff Dan Zarrilli; New York City Office of Long-Term Planning and Sustainability; NYC City Planning 8

9 Wetlands and Shallowing as Jamaica Bay Flood Protection Massive wetland restoration alone in Jamaica Bay only reduces Sandy plus sea level rise flood levels by ~6 inches however, they likely have wave/erosion reduction benefits in smaller storm events Wetland restoration plus channel depth reductions to 2m maximum depth reduces Sandy s water elevations for Jamaica Bay substantially (3-4 feet!) Philip Orton, Stevens Institute 9

10 Modeling & Quantifying Coastal Protection Focus project: Living, Growing Breakwaters, Staten Island and Raritan Bay Wave heights: CONTROL Wave heights: REEF EXPT 10

11 What Are the Unknowns? NEWPCC study led by Arcadis lead PI Hugh Roberts is working on a white paper laying out a research plan Response of natural systems to sea level rise Efficacy of wetlands for stopping erosion, reducing waves Storm tide modeling pretty good a primary area for improvement is in the details of waves and how they impact flows Modeling of water quality, sediment transport, ecosystems, erosion, socioeconomics higher degree of difficulty and uncertainty Philip Orton, Stevens Institute 11

12 Final Conclusions Storm tides in NY/NJ Harbor have worsened since the 1800s and first half of the 1900s Sea level rise is also making flooding higher and more frequent Shallowing unused deep dredged channels could be an effective long-term green strategy for reducing flooding Wetlands can have benefits for reducing waves and erosion We need to quantify their role in smaller more frequent storms They can only reduce flood elevations if they cover a large area; also, not if there are deep channels circumventing them Philip Orton, Stevens Institute 12

13 Sea level (inches) NYC Panel on Climate Change Draft Predictions Horton, R., and many others. A Framework for Rapid Assessment of Climate Hazards in NYC Post-Hurricane Sandy: Part 1, Atmospheric Variables and Part 2, Sea Level Rise. (in prep.) Methods follow: Kopp, R.E., and many others. Probabilistic 21st century sea-level rise projections at a global network of tide Philip gauge Orton, sites. Stevens (submitted Institute to Earth s Future) 13

14 NYC is not The Netherlands Different Hazard Profile There is no such thing as total coastal protection at NYC Focus less on vertical barriers Focus more on elevating systems Focus more on using antifragile systems that bend but don t catastrophically fail POTENTIAL RISK = 9 ft Philip Orton, Stevens Institute 14

15 Scape Team RBD Resilience Philosophy: The Layered Approach physical + social risk reduction and resilience Philip Orton, Stevens Institute 15