We don't have synonyms for sheetwash yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are sheepwash and sheetwise.
(n) :
A thin layer of unchanneled water that flows over land, for example during a storm when the ground is too saturated to absorb any more water; if it lasts long enough, such flow forms rills and then larger channels.
(n) :
A thin layer of unchanneled water that flows over land, for example during a storm when the ground is too saturated to absorb any more water; if it lasts long enough, such flow forms rills and then larger channels.