The horizon

Is it necessary to draw the ground for the reader to identify that a person is walking? The answer is no. This means that drawing the horizon is giving us redundant information. We already know that there is a floor in the moment we see a character walking. If we want to give other information, such as that he is walking on water, we will have to draw the water, because otherwise the reader will know that the character is walking on a ground. If we choose to draw it, it will be to indicate some extra information, which completes the information of the scene. What kind of sky, what kind of soil....

Also the choice to draw it or not can contribute to giving or taking weight to the figure. When the character draws the ground, he is between gravity and the sky and the horizontal force of the ground.