What causes a river to flow backward sometimes?

A river can flow backward when something pushes water the other way, just like when you push a toy boat in a bathtub.

Rivers usually go from high to low, like how water runs off your hands when you wash them. But sometimes, big events, like heavy rain or melting snow, add so much water that it pushes the river backward. It's like if you poured a whole bucket of water into a small stream; suddenly, the water might splash back up instead of just going forward.

Sometimes, a river goes backward not because there’s too much water, but because it wants to go somewhere it already knows. Imagine drawing a line with your finger on a piece of paper, then erasing part of it and redrawing it in the opposite direction. That's what happens when a river changes path: it flows backward for a while until it finds its way again.