NEARSHORE CURRENT SYSTEMS

Water Motion Under Waves vs.. Water DepthWave Base Water Particle Movem ent SHALLOWER WATER Nielsen and Nielsen, 1978 Java: Uni.. of Texas Animated Demos Stokes' 2nd order Wave Theory...

Water Motion Under Waves vs Water Depth

Wave Base

Water Particle

Movem ent SHALLOWER WATER

Nielsen and Nielsen, 1978

Java:

Uni of Texas

Animated Demos

Stokes' 2nd order Wave Theory

Komar, 1976

Radiation Stress

Radiation stress = ”The excess flow of momentum due to

the presence of the waves” (Longuet-Higgins & Stewart 1960)

0

2

0

xx

kh

kh



1

yy

kh

kh

Rip Currents & Cell Circulation

Shallow water

2

xx

S  E   gH

Momentum balance in cross-shore direction:

xx

xx

S

x





h x





H

Komar, 1976

Edge Waves & Cell Circulation

Komar, 1976

Shoals & Cell Circulation

8

xy

n







Longshore component of wave forcing = (1)

where

2

y f m l



Frictional drag on flow = (2)

α b

v l

(1) = (2)

*

5 tan

16

f

C

(Komar and Inman 1970)

(Longuet-Higgins 1970)

Longshore Currents & Oblique Breaking Waves

Longshore current profiles (solid line - no lateral

mixing; dashed lines - with lateral mixing)

(Longuet-Higgins 1970)

Shinnecock Inlet, Long Island, NY

50 km

Tidal Currents

Open-Coast Tidal Currents

Tidal-Inlet Influenced Currents

Ebb-tidal Current

x

Longshore Component of Tidal Current (x)

Time (hr)

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

Channel/10

12 m

140 m

Open-Coast Ti dal Currents Tidal -I nl et Influenced Currents

x Flood

Ebb

Komar, P.D and Inman, D.L 1970 ”Longshore Sand Transport on

Beaches,” J Geophys Res., (75):5914-5927.

Komar, P.D 1976 ”Beach Processes and Sedimentation,” Prentice Hall, NJ.

Nielsen, J and Nielsen, N 1978 ”Kystmorfologi,” Geografforlaget,

Brederup, Denmark (in Danish)

Sonu, C.J 1972 ”Field Observations of Nearshore Circulation and

Meandering Currents,” J Geophys Res., (77):3234-3247.