Virgin River Field Trip

I have been thinking about different field trips and I was wondering about a field trip to the Virgin River. It is the main river drainage for our area and I think it would be a great way for students to see a real habitat. I am teaching fourth grade this coming year and would like to do this. I know it would cover part of our core but I'm not sure of how to tie it in for the students to really focus on the content. If any of you have any lesson plans or ideas about this please let me know?