The evolution of a hump-like density disturbance in a collisionless plasma is considered. The effect caused by the initial shape of the disturbance is demonstrated. In the case of cold ions the development of a collisionless shock wave is observed over a long period of time. The formation of separate ion-acoustic solitons, their reflection from a wall and passage through each other are described. Also the ion temperature effect on the flow is studied. The ion reflection and the formation of a two-stream structure are illustrated.