Meandering channels typically deposit sediments near their inner bank
to form point bars. Laboratory experiments with narrow sharp bends sho
w that under identical flow conditions the configuration of point bars
depends on particle size. Explanation to this grain-size effect is fo
und in a three-dimensional particle stability. Despite favorable secon
dary currents, coarse grains tend to move toward the thalweg and coars
e-grained point bar deposits are eroded as the side-slope angle approa
ches the angle of repose of the bed material. Calculated results coinc
ide with experimental observations. Point bars are considerably smalle
r for coarse-sand deposits than fine sands.