The growth of the bulge near a river mouth

Abstract

Freshwater plumes released under various geomorphologic conditions were investigated numerically. When the initial Froude numbers are fixed in the investigation of the effects of geomorphologic variations, the boundary conditions are controlled by changing depths, bottom slopes and widths of the river channel. Depending on these various conditions, plumes diverge around the river mouth into via several paths to up and down the streams and in an offshore direction. In particular, upstream propagation of a plume is produced by the secondary bulge which rccirculates next to the river mouth, with the bulge appearing to move away from the coastal line with increasing depth, which causes the formation of the main bulge. The growth of the main bulge also depends on the geomorphologic conditions, and its differing patterns can be shown using a series of numerical experiments. To examine the effects of the channel width and other variables on the stratification in this study, the overall Froude numbers were compared to the Rossby numbers. A comparison of the Froude number with the plume surface area also confirmed that with a fixed river channel width, the surface area of a plume increases with increasing the Froude number. As the river becomes wider, the stronger stratification enhances the dispersion of freshwater to a wider area.