Environmental Impact of Tidal Bores in Tropical Rivers

A tidal bore impacts significantly on the estuarine ecosystem, although little is known on the flow field, mixing and sediment motion beneath tidal bores. In the absence of detailed field measurements, a quasi steady flow analogy was applied to investigate an undular tidal bore with inflow Froude numbers 1.6 and 1.25. Experimental results indicated that rapid flow redistributions occur beneath the free-surface undulations, with significant variations in bed shear stress between wave crests and troughs. Dynamic similarity was used to predict detailed flow characteristics of tidal bores with inflow Froude number between 1.3 and 1.6. The effects of periodic loading on river sediments, scour of the riverbed and flow mixing behind the bore were investigated. A better understanding of these processes will contribute to better management practices in tidal bore affected rivers, including the Styx, Daly and Ord rivers in tropical Australia.