Buoyant river plumes and mud deposition in a rapidly extending tropical delta

Abstract

The Solo river, East Java, Indonesia, is a typical monsoonal river. The major part of river discharge and sediment transport is realized during the four or five months of the wet season. River outflow essentially has the character of a buoyant jet. The buoyancy of the effluents gives rise to the development of buoyant river plumes. The properties and behaviour of these plumes are of fundamental importance in the depositional processes which govern delta growth. Deposition rates near the river mouth have been calculated by modelling river outflow and plume dimensions. Simulations of ‘banjir’ events (periods of high discharge) suggest that the average, areal deposition may range from 1 to 10 cm·d −1. The estimated annual changes in bed level exceed values of 1.0 m, even if consolidation is taken into account. Measured changes in bed level, as deducted from echosoundings, show good agreement with model calculations.