high water volume in wet seasons does most of the downcutting in the main canyon. these flood events are responsible for transporting most of the 3 million short tons (2.7 million metric tons) of rock and sediment that the virgin river transports yearly. the virgin cuts away its canyon faster than its tributaries can cut away their own streambeds, so tributaries end in waterfalls from hanging valleys where they meet the virgin. the valley between the peaks of the twin brothers is a notable example of a hanging valley in the canyon.