Energy Attenuation & Hybrid Living Shorelines: A Viable Tool for Coastal Resilience

Transcription

1 Energy & Hybrid Living Shorelines: A Viable Tool for Coastal Resilience Hot Topic Session Delaware Estuary Science & Environmental Summit Balancing Progress & Protection 10 Years of Science in Action January 25-28, 2015 Cape May, New Jersey Douglas Janiec Natural Resources Program Manager & Senior Restoration Ecologist Sovereign Consulting, Inc. Photograph provided by Living Shoreline Solutions, Inc.

2 What does a Hybrid Living Shoreline do? A Hybrid Living Shoreline creates a multi-step wave energy attenuation system by mimicking natural processes. They provide the following benefits: Supports LS Projects in Moderate to High Energy Systems Sediment Conservation Cost Saving for Dune and Nourishment Projects Infrastructure Protects Resilience (50+ years) Barrier Reefs Oyster Habitat Stabilizes Beaches for Horseshoe Crab and Migratory Birds EFH Uplift Sea grass/sav Restoration Page 2

3 Natural Energy System (concept cross section) Existing Beach (mixed dune/beach/marsh/flat system) Arrows Represent Wave Energy MHW Dune, high marsh edge, forest, or other supratidal feature Step 3 (severe storm) Natural Accretion Zone (may be beach, marsh, intertidal bars, and/or SAV) Step 2 (lower energy) Bottom w/o Irregular Feature Feature (i.e. land, sand bar, reef, wide shallows, structure) Step 1 (higher energy) MLW Example of Spacing (ft)

4 Hybrid Energy System (concept cross section) Targeted Resilient Shoreline (mixed dune/beach/marsh/flat system) Existing Beach MHW Existing supratidal feature gets hammered Most or all of Step 2 is absent Existing Bottom Step 1 is gone MLW Step 3 (severe storm) Step 2 (lower energy) Step 1 (higher energy) Example of Spacing (ft)

5 Hybrid Energy System (concept cross section) Targeted Resilient Shoreline (mixed dune/beach/marsh/flat system) Existing Beach MHW Created or existing supratidal feature Passive accretion and/or optional nourishment (may be beach, intertidal bars, and/or some SAV) Existing Bottom Hybrid Structure (n.t.s.) MLW Step 3 (severe storm) Step 2 (lower energy) Step 1 (higher energy) Example of Spacing (ft)

6 Wave Constructive (in phase) Conditions & Destructive Wave (out of phase) Conditions In Phase Out of Phase Page 6

7 Some Wave Basics The longer the wind blows - the bigger the waves The stronger the winds the higher the waves The longer the fetch - the bigger the waves Substrate depth and slope affect wave type and break Relative to the Delaware Bay, these factor limit wave size and energy. Page 7

8 How Wave Energy Interacts with Objects (BBW) Reflection (bouncing) Refraction (bending) Diffraction (wrapping) Page 8

9 An Example Shoreline Erosion Area Constructive Wave Energy Redirectioning and Focusing Destructive Wave Condition Wave Diffraction Apollo Bay, AU

10 Breakwaters & Hybrid Living Shorelines Are Functionally Different Breakwaters provide a complete or partial linear barrier to redirect (manipulate) concentrated wave energy. New hybrid living shorelines allow the wave to pass through the structural array as the wave attenuates (breaks up) and creates a destructive wave environment. Page 10

11 Examples of Breakwaters Erosion Patterns (not accretion patterns). Although some attenuation occurs, much of the energy is still concentrated. Fights with nature.

12 Example of Energy : Cupped Wave Spreader Loop Canal, Bethany Beach, DE Concentrated energy Log Cups Gap Logs Unconcentrated energy; suspended particuates drop out of column Red is refractions over logs Purple is diffraction around logs Cumulatively, the combined wave manipulations result in energy cancellation and attenuation Thank you, Delaware Center for the Inland Bays for sharing Page 12

13 Other Structural Energy Manipulations Energy Focusing/Defocusing Baffled opening in structures Strategic constrictions and enlargements Strategic placement of structures Energy Redirectioning X-Y Planar energy deflections (horizontal vector alterations) Z Planar energy deflections (vertical vector alterations) Microturbulence Page 13

14 Example of Other Manipulations Energy Focusing/Defocusing Energy Redirectioning Microturbulence Figures provided by Living Shoreline Solutions, Inc. Page 14

15 Energy Technology at Work Video provided by Living Shoreline Solutions, Inc.

16 Energy Offers a New Options for Shoreline Resilience Wayfarers (low to moderate energy) Oyster Castles (low to moderate energy) WADs (moderate to high energy)

17 Thank You Douglas Janiec Natural Resource Program Manager Sovereign Consulting, Inc A typical summer evening at the point