Changed channels, in a way

• Sprinkled with flour
• Scraped (river bottom)
• Saved from obscurity, with "up"
• Dipped in flour
• Brought (up), as from the distant past
• Made deeper, as a shipping lane
• Scraped the bottom of
• Coated in flour

Wiktionary Word definitions in Wiktionary
vb. (en-past of: dredge )