EM 1110-2-1100 (Part II)
30 Apr 02
II-7-5. Harbor Oscillations
(1) Harbor oscillations are long-period wave motions that sometimes disrupt harbor activities. The
oscillations are standing waves with typical periods between 30 sec and 10 min. Vertical motions are
generally small, but horizontal motions can be large. Oscillation characteristics are generally controlled by
basin size, shape, and water depth. Oscillations are most damaging when the period coincides with a natural
resonant period of the harbor. The phenomenon is also referred to as harbor resonance, surging, seiching,
and resonant oscillations.
(2) Harbor oscillations can be a significant problem for inner harbor components and moored vessels
within a harbor basin. Resonant periods characteristic of moored vessels often fall into the same range of
periods as harbor oscillations. Thus, harbor oscillations can create dangerous mooring conditions including
breaking of mooring lines, damage to fender systems, vessel collisions, and delays of loading and unloading
operations at port facilities.
(3) Processes and estimation procedures for harbor oscillations are discussed in this section. Discussion
of harbor oscillations is generally presented in terms of the characteristics in Table II-7-2.