dredging
幹法塗搪; 疏濬
Dredge v. t. [imp. & p. p. Dredged p. pr. & vb. n. Dredging.] To catch or gather with a dredge; to deepen with a dredging machine.
Dredging machine, a machine (commonly on a boat) used to scoop up mud, gravel, or obstructions from the bottom of rivers, docks, etc., so as to deepen them.