Whitewater Rapids

We're Scotty, Kohner, Rasheed, and JB, and we're taking our first rafting trip down the American River. We know that parts of the river are calm, but other parts have some rockin' rapids with crazy names like Satan's Cesspool. We want to figure out how the river is going to push our raft around, so we can get through safely. Our question: How does the elevation change in the river relate to the difficulty of the rapids, and how should we paddle in those tough spots?

How would you investigate this question?
Decide how to measure river properties such as elevation, elevation change, and flow rate. What about special features in the river, such as large boulders, or places where the river narrows or widens? How does the water flow in each of these places? Devise a way to test your ideas with a model. Describe your ideas in your notebook. Then discuss them with your teacher, or go to Whitewater Rafting to learn how Scotty, Kohner, Rasheed, and JB did their river investigation.