We wanted to find out how a river is formed so we made one of our own.
First we filled some guttering full of earth, stones, brick and some twigs. We made sure the guttering was on a slope because a river always runs down hill.
Then we made a river by running water from a hose down it and saw what would happen.

We discovered that when rivers are blocked by obstacles such as boulders and dams, the water finds a way to pass going under or around it.

Where the water changed direction the water got deeper. The reason why it became deeper is that the water had to change direction because the earth and the rocks were blocking its way. It became deeper because the water that was trying to go around the brick was slowing down to change direction and the water behind it was building up and getting higher.

In this picture the water has washed away some of the earth so that it has uncovered some stones, rubble, rock etc.
In this picture the water has found a path to flow through and that has moved some earth and has made a waterfall and small tunnels to flow through.
Water is strong enough to move and carry obstacles in its way.