The coastal depositional system of a small mountainous river: a perspective from grain-size distributions

• Published in: Marine geology 2000-04, Vol.165 (1), p.63-86
• Main Authors: Liu, J.T., Huang, J.-S., Hsu, R.T., Chyan, J.-M.
• Format: Article
• Language: English
• Subjects: Coastal depositional system; EOF analysis; Grain-size distribution; Marine; Morpho-textural relationship; River sediment discharge; Sediment transport; Taiwan, Tseng-Wen Estuary; Wave sorting
• ISSN: 0025-3227; 1872-6151
• DOI: 10.1016/S0025-3227(99)00131-0

Tseng-wen River is a small mountainous river on a wave-dominated coast of Taiwan. The spatial distribution patterns of 17 individual grain sizes offshore near the river mouth show strong morpho-textural relationships with the bathymetry, which also vary considerably according to the grain size. The influence of seven hypothetical factors that could affect the observed grain-size patterns were examined individually by using a methodology that combines ‘filtering’ concept and a multivariate analysis technique (EOF). These factors include the sediments discharged by the river, offshore palimpsest sediments, sediments eroded from a submarine sand ridge and the remnant river delta, the effect of wave sorting, and the northward and southward littoral drift. The study results indicate that the Tseng-wen River is the most important source for modern sediments in the study area. The reworking of offshore palimpsest sediments is also an important sediment source. The agitation by waves is an important sorting mechanism in the study area, and the net sediment transport in the study area is northward. The findings based on grain sizes are also corroborated by short-term observations of the near-bed sediment dynamics and transport during the flood season of the Tseng-wen River.