Wadi, alternatively wād, Maghrebi Arabic Oued, Hebrew: וָאדִי, romanized: wadi, lit. 'wadi') is the Arabic term traditionally referring to a river valley. In some instances, it may refer to a wet (ephemeral) riverbed that contains water only when heavy rain occurs.

An arroyo, from Spanish arroyo, also called a wash, is a dry watercourse that temporarily or seasonally fills and flows after sufficient rain. Flash floods are common in arroyos following thunderstorms.