Source : Webster's Revised Unabridged Dictionary (1913)

Aggrade \Ag*grade"\, v. t. [imp. & p. p. {Aggraded}; p. pr. &
   vb. n. {Aggrading}.] (Phys. Geog.)
   To bring, or tend to bring, to a uniform grade, or slope, by
   addition of material; as, streams aggrade their beds by
   depositing sediment.

Source : WordNet®

aggrade
     v : build up to a level by depositing sediment [ant: {degrade}]