Made deeper, as a shipping lane

• Sprinkled with flour
• Deepened, as a canal
• Brought (up), as from the distant past
• Dipped in flour
• Scraped (river bottom)
• Saved from obscurity, with "up"
• Scraped the bottom of
• Unearthed (with "up")
• Hauled up (from depths)

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