Coriolis effect

I think this would have made a better video than a still. After a heavy downpour, the water coming down the upper parking lot (car park) came down the channel to the drain. At which time it rotated anti-clockwise, more by aim than force.

noun: Coriolis effect; noun: Coriolis force; plural noun: Coriolis forces

an effect whereby a mass moving in a rotating system experiences a force (the Coriolis force ) acting perpendicular to the direction of motion and to the axis of rotation. On the earth, the effect tends to deflect moving objects to the right in the northern hemisphere and to the left in the southern and is important in the formation of cyclonic weather systems.