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