Journal of Oceanography and Marine Research
Open Access
ISSN: 2572-3103
+44 1300 500008
ISSN: 2572-3103
+44 1300 500008
Kiril Bahcevandziev* and Saviour P. Udo-Akuaibit
An intensive field study on near-shore infra-gravity wave motions was carried out to ascertain its oscillation patterns and effects on shoreline morphodynamics at the downdrift shoreline, east of Qua-Iboe River estuary, South-East coast of Nigeria. Time-series measurements of wave run-up swash periods over a neap-spring tidal cycle and daily beach profile surveys were made at the shoreline. Detailed analysis of the result revealed a dominance of gravity waves over infra-gravity wave oscillations in the wave spectra with average percentage frequencies of occurrence of 52.28 and 47.72 respectively. The infra-gravity wave spectrum is further filtered into first harmonic group (121 s-150 s), second harmonic group (91 s-120 s), third Harmonic group (61 s-90 s) and fourth harmonic group (31-60s) of oscillation periods. The first harmonic group of infra-gravity waves were noted as the principal agents of erosion and sedimentation on the beach. In addition, the first harmonic group scour sediment and trigger-off erosion on the shoreline while the short period harmonics of infra-gravity waves transport, spread, winnow and sort sediments accordingly. The gravity waves are responsible for compaction of sediment. Moreover, the oscillation pattern of the infra-gravity waves in the dissipative surf-zone shows regular and harmonic motions for which a full wavelength is propagated at every 2-3 minutes interval as the beat, and independent of tidal stage (flood or ebb). It also plays significant role in the self-cleansing potential of the surf-zone. An understanding of the energy radiation and transmission by the fourth harmonic group of infra-gravity wave oscillations is considered essential in the engineering design and management of shoreline protection, marinas and sea ports.
Published Date: 2024-06-30; Received Date: 2020-07-28