Where two streams (or rivers) join, the smaller one is called the tributary. The place where the two streams join is called the confluence.

These pictures shows a tributary coming under a bridge, through a pipe, to join the Bourn Brook.

Where lots of streams join together they form a network of streams, or a 'stream network'. This map shows how the Bourn Brook joins with a number of other streams.

When enough streams have joined together they form a larger channel, called a river. Rivers join together to form a 'river network'. This map shows that the Bourn Brook flows into the River Rea and then the River Tame.

The River Tame flows into the River Trent, which eventually flows into the sea.