Such oscillations not only present hazards to navigation and shoreline communities but also play important roles in the dynamics of benthic communities.
Seiches can cause water bodies to oscillate at different wavelengths known as modes.
The period of a seiche harmonic is approximately equal to the fundamental seiche period divided by the number of nodes in the harmonic. If the fundamental mode shown in the top diagram has a period of 120 seconds, the harmonic modes shown in the center and the buttom diagrams have periods of approximately 60 and 40 seconds, respectively. Whether a maneuvering vessel runs aground during a seiche or moves laterally off course depends on wind speed and direction, vessel dimensions and performance, water depth, and the magnitude and timing of the seiche. It also depends on the vessel's position relatve to the composite pattern of seiche nodes and antinodes that is created when the fundamental mode is superimosed on its harmonics.