Practical Application of Theory for Tidal‐Intrusion Fronts

Abstract

A simple theoretical model was applied to interpret the characteristics of an estuarine front that forms at the early stage of each flood tide off Newport News Point, in the lower James River, Virginia. The observed depths of diving of denser water at the front, and the upriver movement of the front are explained theoretically. The construction of a man‐made island to facilitate port expansion was proposed for downriver of the front. Its effect on the flood current approaching the front is quantified with a vertically averaged two‐dimensional numerical model. The theory is used to predict the impact of the proposed island on the frontal characteristics, particularly with respect to the entrainment and transport of oyster larvae to the lower portion of the water column, where net transport is upriver toward seed‐oyster beds. Applications of the front theory, results of the numerical model, and oyster‐larvae studies indicate that the transport capacity of the front would be markedly reduced by island construction at the proposed sites.