Peculiarities of the coastal flows in a water reservoir are mainly conditioned by a bottom geometry and coastal curvatures. The periods of conducting water layer cooling initiate an intensive vertical exchange which in turn generates a complex structure near the coastal flow. Such a mechanism of generation of flows is connected with evolution of the convective instability in a reservoir and significantly differs from the known mechanisms of wind and wind wave flows. The numerical modeling of the convective mode involves a necessity of direct reproduction of coherent structures stochastic ensemble. For this purpose an eddy resolving model of the upper mixed water layer with allowance for bottom roughness is used. The model results are used in solving the problem of the oil admixture transport in conditions of intensive surface cooling.