Final answer:
The gradient of a river is the vertical drop divided by the channel length, and it is typically measured in feet per mile. To calculate the gradient of the Bighorn River and its unnamed tributary, divide the vertical drop by the channel length.
Step-by-step explanation:
The gradient of a river is the vertical drop divided by the channel length and is typically measured in feet per mile. To calculate the gradient of the Bighorn River and its unnamed tributary, you would need the vertical drop and channel length of each. Once you have those measurements, you can divide the vertical drop by the channel length to determine the gradient. For example, if the Bighorn River has a vertical drop of 500 feet and a channel length of 100 miles, the gradient would be 500 feet per 100 miles.