PPT Slide
Notes:
In the canyon downstream, rapid downcutting of the main channel has caused rapid incision of valley walls and side canyons, introducing large boulders that mostly mantle the bedrock below the channel. Clearly this locally-derived coarse sediment must be eroded before appreciable further downcutting of the main channel can occur. Thus there can be a negative feedback between channel incision and further erosion, in that the incision results in importing coarse debris from valley sides and steep headwalls that must also be eroded before further downcutting.