artificial reef design for surfing by: spicer bak, m.s. stevens institute of technology this...

Artificial Reef Design for Surfing

Artificial Reef Design for Surfing

By: Spicer Bak, M.S.

Stevens Institute of Technology This material is based upon work supported by the National Science Foundation under Grant No.. NSF DGE-0742462

By: Spicer Bak, M.S.

Stevens Institute of Technology This material is based upon work supported by the National Science Foundation under Grant No.. NSF DGE-0742462

Why do this?Why do this?

• Rising Sea Levels/Wave heights

• Growing Conflict with Surfer

Groups and local

Government

• Rising Sea Levels/Wave heights

• Growing Conflict with Surfer

Groups and local

Government

Long Branch, NJ - October 2006ASBPA National Conference

Beach ProtectionBeach Protection

• Waves are a type of energy– Waves = energy– Energy moves sand– Beach gets narrower

• 2 basic causes of erosion– Longshore Sediment transport – Cross-shore erosion

• Current popular protection– Groynes - Long-shore– Breakwaters/seawalls

• Cross-shore

• Waves are a type of energy– Waves = energy– Energy moves sand– Beach gets narrower

• 2 basic causes of erosion– Longshore Sediment transport – Cross-shore erosion

• Current popular protection– Groynes - Long-shore– Breakwaters/seawalls

• Cross-shore

Groynes - Long-shore sediment transport protectionGroynes - Long-shore sediment transport protection

• Advantage: – Keeps sand– Encourages sea life

• Disadvantage– Eyesore - not pretty– Need a field to

adequately protect

• Advantage: – Keeps sand– Encourages sea life

• Disadvantage– Eyesore - not pretty– Need a field to

adequately protect

http://changingcoastline.com/dunes-edge/beach-restoration/hard-engineered-solutions/

Break waters & sea wallsBreak waters & sea walls

• Seawall– Wall at edge of water – Stops wave energy

• Breakwater– Parallel to shore – Dissipates waves

• Seawall– Wall at edge of water – Stops wave energy

• Breakwater– Parallel to shore – Dissipates waves

Galveston, Texas

Science Of Surfing Science Of Surfing

• Peel Angle

• Velocity

• Wave Classification– Vortex Ratio– Surf Similarity

Parameter

• Peel Angle

• Velocity

• Wave Classification– Vortex Ratio– Surf Similarity

Parameter

Peel AnglePeel Angle

• Used to classify the wave

• Surfer Velocity

• Used to classify the wave

• Surfer Velocity

sin

WS

VV bW ghV

Peel AnglePeel Angle

Hutt, Black and Mead (2001)Hutt, Black and Mead (2001)

BEGINNER

INTERMEDIATE

ADVANCED/EXPERT

Classification of Waves

Vortex RatioVortex Ratio

Wave parameters used for curve fitting; vortex length (l), vortex width (w), angle (θ), and wave height (H), orthogonal seabed gradient (X’)

821.0'065.0 XY

cos' XX

Vortex ratio (Y) = Vortex length to width ratio

Mead and Black (2001)

Surf Similarity ParameterSurf Similarity Parameter

ob

b

LH

tan

Surf Similarity Parameter

ξb > 2.0 0.4 < ξb < 2.0 ξb < 0.4

Breaker Type Surging or collapsing Plunging Spilling

Surfing Terminology

‘Unsurfable’ wave ‘Tubing’ or ‘hollow’ wave

‘Full’, ‘fat’, or ‘mushy’ wave

Surging/Collapsing Plunging Spilling

Example ClassificationsExample Classifications

Mead and Black (2001)

Reefs Reefs

• Advantages– Out of sight– Design to protect against

long- shore/cross-shore– Provides:

• Capability for design for surf

• Adds marine life habitat

• Sheltered swimming

• Diving

– Comparable Cost

• Advantages– Out of sight– Design to protect against

long- shore/cross-shore– Provides:

• Capability for design for surf

• Adds marine life habitat

• Sheltered swimming

• Diving

– Comparable Cost

• Disadvantages– Construction difficult– Time consuming– Still an emerging

technology– Mostly proprietary (as

of right now)

• Disadvantages– Construction difficult– Time consuming– Still an emerging

technology– Mostly proprietary (as

of right now)

Refraction - EnergyRefraction - Energy

o

o

sinsin

C C

o

o

sinsin

C C

• Wave straightens out

• Snell’s Law

( – measured w.r.t. shore normal)

• E=1/8 * g * H2

• Wave straightens out

• Snell’s Law

( – measured w.r.t. shore normal)

• E=1/8 * g * H2

Unprotected Unprotected

Coastal protectionCoastal protection

DesignDesign

• Giant Sand bags– Placed then filled

• V - Shaped pattern

• Giant Sand bags– Placed then filled

• V - Shaped pattern

Narrow Neck - AusNarrow Neck - Aus

• Both Right and left– Beginners wave on

inside

• Both Right and left– Beginners wave on

inside

ASRASR

• design overview

• india goes off

• design overview

• india goes off