Answer:
You are using the Linear Perspective principle.
Step-by-step explanation:
This principle creates an illusion of depth. Instead of drawing a river with a flat appearance, you decided to create depth using lines that part from the canvas center (horizontal line), begins to separate themselves (vanishing point) and ended on both sides of the canvas (parallel lines). This simple process just works if you use its three principles: parallel lines, a vanishing point, and the horizon line.