Net sediment transport patterns inferred from grain-size trends, based upon definition of “transport vectors”

Abstract

A new approach to the analysis of the grain-size trends, associated with net sediment transport directions in shallow marine environments, is developed here. Two specific trends, modified from McLaren and Bowles (1985) on the basis of a literature review, are used to define a grid of “trend vectors”. Such vectors are filtered and transformed into “transport vectors”. It is suggested that an ordered pattern of the transport vectors represents net transport paths. The orderliness of the derived pattern is examined on the basis of a significance test, using the average length of the transport vectors as a criterion. Both the filtering operation and the significance test procedure are based upon the assumption that the trend vectors which are not associated with net transport have the same probability of being in any direction. The technique is applied to data from Yangpu Harbour, southern China. The technique can be applied to inner continental shelf and coastal environments. For such an analysis, the area under investigation should be sampled at an interval large enough to reflect the real grain-size trends resulting from net sediment transport, but small compared with the dimensions of the sedimentary environment. The time-scale of the results depends upon the sampling depth. Applicability of the technique is likely to be somewhat limited, where the environment is highly variable over short distances. Furthermore, due to its statistical character, the analysis may fail to identify net transport patterns.