Tidal-fluvial Processes at the Outlets of Delta Distributaries: A Multi-cruiseObservational Study

Ji, X.-M.; Yang, Y.; Fang, Y.-J., and Zhang, W., 2020. Tidal-fluvial processes at the outlets of delta distributaries: A multi-cruise observational study. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1449-1453. Coconut Creek (Florida), ISSN 0749-0208.The hydrodynamics in delta distributaries has tremendous impact on sediment transport, water quality and deltaic ecosystems; yet many processes acting at the riverine-esturarine interface of a delta are not well understood. This contribution investigates the interplay between riverine runoff and tidal motions at the outlets of delta distributaries. We focus on the tidal-fluvial processes at eight outlets of three main distributaries of the Pearl River Delta, China. The field measurements of water levels, discharges, velocities at the eight outlets were conducted synchronously for five times, with three times in wet season during spring, moderate and neap tides, respectively, and once in normal season, once in dry season. The observations reveal that the tidal asymmetry in the Pearl River Estuary is largely influenced by river discharge. The tidal velocity amplitudes depend mainly on the river discharge and tidal prism. To be specific, while during low discharge conditions the presence of a river discharge decreases tidal velocity amplitudes, during very high flow regimes the effect of tides at the distributary outlets is magnified with a noteworthy increase in tidal velocity amplitudes.