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Long period oscillations in the longshore current on a sandy, barred coast investigated with singular spectrum analysis

100%
Kaczmarek J., Rozynski G., Pruszak Z.
Oceanologia
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2005
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tom 47
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nr 1
The presence of infragravity waves in nearshore regions can be sought in the records of both water levels and wave-driven longshore currents. For this reason, time series of such currents in close proximity to the shoreline were analysed using Singular Spectrum Analysis (SSA). Simultaneously, the results obtained with this method were confronted with the output of Discrete Wavelet Transform (DWT), which had previously been applied to this data. The records of longshore currents were collected on a daily basis during field experiments in the autumns of 2002 and 2003 with sampling rates of 3 Hz and 0.5 Hz. This produced a large data set that allowed for the use of an advanced signal processing technique, capable of extracting patterns characteristic of low-, medium- and high-frequency bands. It provided similar evidence to that produced by DWT for the existence of infragravity waves along a dissipative coast with multiple bars. The study also demonstrated the utility of SSA for studies on coastal hydrodynamics. It also showed up the better user-friendliness of DWT in terms of pattern extraction and interpretation. On the other hand, SSA demonstrated a higher precision of pattern extraction once the DWT output was known, which is a manifestation of the synergy of the two methods when applied jointly.
2
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Coastal processes of Central Tamil Nadu, India: clues from grain size studies

100%
Angusamy N., Rajamanickam G. V.
Oceanologia
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2007
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tom 49
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nr 1
The sediments of the beaches along the central coast of Tamil Nadu from Pondicherry to Vedaranyam were studied for their textural variation. 108 sediment samples collected from the low-, mid-, and high-tidal zones, as well as the berms and dunes of different beach morpho-units were analysed. The study area was divided into three sectors (northern, central and southern) on the basis of prevailing energy conditions and oceanographic parameters. The poorly sorted, negatively skewed, coarser sediments of the northern sector are indicative of denudational processes taking place there. Medium-to-fine, moderately-to-well sorted, positivesymmetrically skewed sediments dominate the central sector, probably as a result of the influence of palaeo-sediments deposited by rivers from inland as well as by waves and currents from offshore. Fine, poorly sorted, positive-symmetrically skewed sediments dominate the southern sector, highlighting depositional processes. Linear Discriminant Function Analysis (LDF) of the samples indicates a shallow marine environment origin for all the three sectors. These results show that reworked sediments, submerged during the Holocene marine transgression, are being deposited on present-day beaches by waves, currents and rivers in the study area.
3
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Morphological and lithodynamic conditions in the marine coastal zone of the Vistula Spit (Gulf of Gdansk, Baltic Sea)

84%
Kobelyanskaya J., Bobykina V. P., Piekarek-Jankowska H.
Oceanologia
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2011
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tom 53
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nr 4
The paper presents a lithodynamic interpretation of the Polish-Russian morpholog- ical and lithological research project along the marine coastal zone of the Vistula Spit, carried out between July and September 2008. 78.4% of the coastal zone is characterized by a balanced environment, with fractional transport of sediments as bed and suspended load. Deposition was observed in 8.2% of the study area. A dynamic environment with a deficit of bed material, local turbulences and erosive trends were found in 13.2% of the coastal zone. The critical erosive current velocities vary from 16 to 20–26 cm s−1.
4
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Relationships between coastal processes and properties of the nearshore sea bed dynamic layer

84%
Ostrowski R., Pruszak Z.
Oceanologia
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2011
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tom 53
|
nr 3
The paper discusses the notion of a layer of sandy sediments overlying a substratum of cohesive deposits in the coastal zone. This layer of sand is generally more mobile and is therefore conventionally referred to as the dynamic layer. Its parameters are important to coastal lithodynamic and morphodynamic processes caused by waves and currents. On the other hand, the dynamic layer is formed by nearshore hydrodynamic impact. The variability of the features of the dynamic layer on the southern Baltic dune and cliff shores in Poland is analysed on the basis of selected geological data supported by local seismo-acoustic field investigations. It appears that the conventional notion of the dynamic layer makes sense only in specific geomorphologic conditions. In such cases, mostly related to cliff shores, theoretical modelling of sediment transport should take the properties of the dynamic layer into account.
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