Desert washes and arroyos: collecting in dry stream beds

Desert washes are dry for most of the year but function exactly like a stream bed during the rare heavy rain events that do occur, meaning the same sorting principles that concentrate material in a permanent creek apply here too, just compressed into infrequent, sometimes violent flash flood events rather than steady year round flow. This makes washes genuinely productive for tumbled agate, jasper, and petrified wood in many desert regions. The real safety point worth repeating here, never enter a wash or narrow canyon when rain is falling or threatening anywhere upstream, flash flooding in these environments moves fast, can arrive with little warning, and is a genuine, well documented cause of death in desert regions every year.