Evaluation of sediment transport formulae for estuary conditions: Boyne Estuary: case study

The problem of sediment transport and sedimentation in estuaries is examined in relation to the Boyne Estuary situated on the Central Queensland Coast. Bottom material characteristics are examined and the most appropriate formulae for prediction of sediment transport are identified.. Estuaries are natural resources that play an important role in the economic and social development of nations. They offer habitat for fish, sites for harbours, industries, and recreational activities. Sediment transport into estuaries, and the subsequent shoaling of estuaries are important estuarine processes that impact upon the physical condition (shape, depth etc) of the estuary, and therefore the uses to which the estuary can be put. As such, estuaries represent important and complex engineering problems. The sediment transport aspect of these estuarine processes is examined in this thesis with a view to quantifying the sediment transport rate in the Boyne Estuary on the Central Queensland coast of Australia. The estuary was characterised into five distinct zones using the particle size distribution of the bottom materiaL A null point, at which the velocity of the river current is effectively balanced by the velocity of the incoming tidal and coastal current was identified in one of the five zones. Analyses of the sediment transport rate were carried out using the depth of flow, mean velocity of flow, bottom roughness and characteristics of the bottom material ofthe Boyne Estuary. Sediment transport formulae reported in the literature are reviewed for this purpose with six formulae, namely, the Ackers-White formula, the Engelund-Hansen formula, the Inglis-Lacey formula, the Van Rijn formula, the Ranga Raju formula, and the Zanke formula, being selected for detailed study. Three of the six formulae (the Van Rijn formula, the Ranga Raju formula, and the Zanke formula) predict the components of the total sediment transport, namely, the bed load transport, and suspended load transport separately. The other three formulae predict the total sediment transport without any detail on the components. Wash load transport is not considered in any of the formulae. The Van Rijn formula was selected as the reference sediment transport formula and three other sediment transport formulae, namely, the Ackers-White, the Engelund-Hansen, and the Inglis-Lacey, that predict close results with the reference formula were found to be suitable for the evaluation of sedimenttransport rate in the Boyne Estuary.