A mathematical model was developed to study how water moves through rock slopes during rainfall. By using a computer program, researchers found that rain quickly saturates the surface and deeper areas of the slope, with water moving downwards. The pressure of the water changes from high to low and then back to high as it flows through the slope. Negative pressure decreases over time, and the water pressure continues to rise even after the rain stops. The highest water pressure is reached a couple of days after the rain ends. This model can help engineers analyze slope stability and design drainage systems for slope projects.