Final answer:
The side canyon at the western end of Unaweep Canyon does not have a specified name, but it likely shows evidence of erosion by a river. Features like canyon walls and water streams, similar to those in the Grand Canyon region, suggest a river carved the landscape.
Step-by-step explanation:
The question pertains to identifying a side canyon that connects with the Unaweep Canyon on its western end, and the evidence suggesting it was carved out by a river. Although a specific name of the side canyon is not provided, one can surmise that it is a characteristic side canyon of the Colorado Plateau, similar to those found in the Grand Canyon region, with features indicating river erosion such as smoothed rock surfaces and deep, linear cuts. The presence of water streams joining a larger watercourse, descriptions of canyon walls that display variations in shape and depth, and the geological formations, all serve as evidence for a river or water flow shaping the landscape over time.
These descriptions bring to mind the well-documented processes that have shaped the Grand Canyon, such as the Colorado River cutting through layers of sedimentary rock, visible in panoramic views of the region. The evidence of a river's work could include the presence of a main stream of water, old trails following shallow washes indicative of water flow, and cross bedding in sedimentary structures, all of which are likely found in the Unaweep Canyon's side canyons as well.