What type of river is the oued or wadi found in the valleys of North Africa and Arabia?

Wadi (or oued) is the Arabic term traditionally referring to a valley. In some instances, it may refer to a dry (ephemeral) riverbed that contains water only during times of heavy rain, a so-called episodic river. Periodic / Non-Perennial Rivers only flow during the rainy season. Exotic Rivers rise in humid areas with high rainfall and flow through dry areas.