EM 1110-2-1100 (Change 1)
31 Jul 03
INTERNAL WAVES
Waves that occur within a fluid whose density changes with depth, either abruptly at a sharp surface of
discontinuity (an interface), or gradually. Their amplitude is greatest at the density discontinuity or, in the case of a gradual
density change, somewhere in the interior of the fluid and not at the free upper surface where the surface waves have their
maximum amplitude.
INTERTIDAL
The zone between the high and low water tides.
IRREGULAR WAVES
Waves with random wave periods (and in practice, also heights), which are typical for natural wind-induced waves.
IRROTATIONAL WAVE
A wave with fluid particles that do not revolve around an axis through their centers, although the particles
themselves may travel in circular or nearly circular orbits. Irrotational waves may be PROGRESSIVE, STANDING,
OSCILLATORY, or TRANSLATORY. For example, the Airy, Stokes, cnoidal, and solitary wave theories describe
irrotational waves. Compare TROCHOIDAL WAVE.
ISOBATH
A contour line connecting points of equal water depths on a CHART.
ISOPACHYTE
Line connecting points on the seabed with an equal depth of sediment.
ISOVEL PATTERN
See HURRICANE WIND PATTERN.
ISTHMUS
A narrow strip of land, bordered on both sides by water, that connects two larger bodies of land.
Appendix A Glossary of Coastal Terminology
A-41
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