Influence of river discharge on tidal and subtidal flows in a microtidal estuary: Implication on velocity asymmetries

•River discharge shows evident effects on the tidal propagation, subtidal flows, and velocity asymmetries within the Caloosahatchee River Estuary.•The upper part of the estuary responds differently from the lower estuary to changes in freshwater discharge. With increased river discharge, baroclinic circulations are enhanced in the lower estuary and suppressed along the river channel.•Modifications of subtidal flows and velocity asymmetries triggered by the increase of freshwater discharge, exhibit three-dimensional characteristics.•We present a modification of the method proposed by Nidzieko (2010) to account for the effect of subtidal flows on the velocity skewness.•Primary contributors to velocity asymmetries are identified and manifested as decreased interactions between semidiurnal and diurnal constituents and increased interactions between semidiurnal tides and subtidal flows.