Abstract: The artificial instantaneous discharge of dredged sediments in flowing waters is usually subjected to cross-flow action In shallow waters the initial discharge and cross-flow conditions are significant for the deposition pattern.T he determination of the characteristics of this problem is thus important before environmental impact assessment can be made.In the present study,a series of laboratory experiments are carefully conducted to investigate the transport and mixing of an isolated sand cloud in cross-flow.The results show that the sediment cloud is dispersed under the forces of buoyancy,gravity,drag force and turbulence of cross-flow The cross-flow is the main driving source for the advection of sediment cloud.The turbulence of cross-flow increases the mixing of sediment cloud and the ambient flowing water,and destroys the double vortices occurring in the stagnant water Thus the vertical frontal position and longitudinal width increase The analysis of experimental data gives the empirical constants and their variance,which can be used to determine the relationships of non-dimensional vertical frontal position and time,longitudinal width and time,and vert ical frontal position and longitudinal width All these results can be used to assess the environmental impact of dumping projects.