The head of flow refers to the vertical distance between the water surface and a specific point in the soil. The uplift pressure in soil increases with an increase in the head of flow. This is because a higher head of flow exerts more pressure on the soil particles, leading to an increase in the buoyant force acting on the soil. As a result, the uplift pressure on the soil also increases, which can have consequences for the stability and performance of underground structures such as foundations and retaining walls.«Soil pressures on pile shaft due to spudcan penetration in clay»