On the nature of “periodic” river bends

The formation of bends (meanders) can be described by a simple physical model, according to which, water flow in a gentle valley with gentle slopes, once deflected by a random obstacle, starts oscillating from one slope to another, while keeping moving down the valley. The sinuosity of the river (the ratio of the path along its channel to the direct path along the valley) depends on the ratio of the steepness of the slopes and the valley; the mean sinuosity is close to 1.5 in accordance with the available geographic data.