EM 1110-2-1100 (Part II)
30 Apr 02
(a) Horizontal currents can modify surface gravity waves by stretching or shrinking features of a wave
train. This distortion can produce a "Doppler Shift" in wave period. Wave orthogonal, crest, and ray
directions are modified (see Part II-1 for definitions). Also, a current modifies surface waves by causing an
exchange of energy between wave and current. The pressure field accompanying the wave also is modified.
Predicting current-modified wave energy, heights, directions, and pressures is typically a complex procedure
still under research; however, a graphical method presented by Herchenroder (1981) based on work by
Jonsson et al. (1970), can be used to estimate the effect of current on wave height HA, where this is wave
height without current.
Using the equation:
H ' (RH) HA
(II-6-29)
(b) Figure II-6-34 may be used to determine RH, the wave height factor, which depends on:
Figure II-6-34. Contours of dimensionless wave height factor RH given by Equation II-6-29.
Waves cannot propagate for values of F and Ω lying in the forbidden region (boundary line F
= FM)
II-6-40
Hydrodynamics of Tidal Inlets
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