Diverting a stream may be done for a variety of different reasons. During heavy rains, a large amount of water could suddenly form its own stream through your yard or your house, causing damage to your landscaping or a structure. A stream may also need to be diverted so something can be built beside it, like a garden. Or maybe you just want to see if you can change the natural course of flowing water on your own. Whatever the reason may be, you can effectively divert a stream to flow, at least temporarily, in a different direction using only shovels.
Dig Beside the Stream
As a stream of water is surprisingly powerful and will try to flow in the direction that is has flowed in the past, the easiest way to divert a stream is to dig into the Earth beside it, below the current level of the stream itself. Make sure the water has somewhere to flow. This means the ditch should either reconnect with the original stream or should find a new path downhill due to the ditch you just dug. Dig this lower level ditch first, without any water flowing into it.
Observe How the Water Flows
Break down the barrier between your new ditch and the flowing water. Observe how it flows into the ditch and if it is going to go where you want it to or if it will simply pool and flood the area. If the latter happens, you can always dig the stream back to where it was originally flowing nearby. If the stream seems to have been effectively diverted then pile soil, stones or other objects along the bank of the new ditch to give it strength against the constantly flow of water.
Build Up the Old Stream
With the Earth you have dug up from the diversion ditch, pile it onto the area where the stream formerly flowed over. This will give the diversion ditch you have just dug strength and keep the stream from returning to where it flowed in the past.