1) Bottom 2) Creek bed 3) It holds running water 4) Rock locale 1) Wadi 
The channel being occupied or formerly occupied by a stream.
any long, narrow, sloping depression on land that is shaped by flowing water. Streambeds can range in width from a few feet for a brook to several ... [5 related articles]
The channel through which a natural stream of water runs or used to run, as a dry streambed.
[n] - a channel occupied (or formerly occupied) by a stream
creek bed noun a channel occupied (or formerly occupied) by a stream
the channel in which a stream flows or formerly flowed.