This often indicates either a barrier in the way of your progress or a situation you are passing through or even trapped in. The edge of the canyon can be a threat of death if you fall, and so you are meeting whatever feelings you have about dying. See: Death.
If there is water running through the canyon it shows there are emotions involved – either calm or powerful depending on the dream See: Valley.
Occasionally the canyon is a place of beauty you are exploring, and this shows you meeting the healing natural feelings within you.
Useful questions:
What is my relationship with the canyon and how am I meeting that in life?
Is this about something blocking my progress, or something I can’t find a way out of?
If there is a flood, what emotions am I facing at the moment?
