area covered by a river along with its tributaries is called what
uk/bitesize/ks3/geography/physical_processes/rivers_flooding/revision/3 / This may help you.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
http://www.bbc.co.uk/bitesize/ks3/geography/physical_processes/rivers_flooding/revision/3/
This may help you.