What it means
A wash is a desert streambed that is usually a strip of sand, rock and mesquite and occasionally, for a few hours after a storm, a brown, fast, loud river. Arizona uses the word where the rest of the country says creek, gully or ravine, and Scottsdale is cut by hundreds of them, from ankle-deep runnels behind subdivisions to broad channels with bridges over them. The desert floor sheds rain rather than absorbing it, and the washes are where it goes.
Locals use the word two ways. “A wash” is any of them: the dry wash behind the house, the sandy wash a trail follows, the one the javelina use as a highway at dusk. “The Wash,” capitalized in speech if not in print, is Indian Bend Wash, the drainage that runs down the middle of the city and is now the Greenbelt, eleven miles of parks, lakes and paths built to flood. “Meet you on the Wash” means somewhere on the bike path.
You will also meet the word on yellow signs at road dips: do not enter when flooded. The monsoon field manual calls ignoring them the one thing that kills people.
Where you’ll meet it
The Greenbelt, from Tempe’s border north past Shea; trail names like Lost Dog Wash in the Preserve; dip crossings on desert-edge roads in north Scottsdale; and every hike that uses a sandy wash bed as its trail.
Where the word came from
Wash is an old English word that the American West bent to a new meaning. Merriam-Webster gives the regional sense, chiefly Western, as “the dry bed of a stream,” also called a dry wash, a channel defined by what the water does when it comes, which is wash everything out. Who first used it this way in Arizona is not recorded. The Spanish word for the same landform is arroyo, which survives in place names across the Southwest; Arizonans mostly say wash.
Scottsdale’s most important wash made the word civic. Indian Bend Wash runs about twelve miles through the middle of the city. For most of the twentieth century it was a dry channel that neighborhoods were built across. On June 22, 1972, a stalled thunderstorm dropped 3.85 inches of rain in about 80 minutes; the wash ran bank to bank, destroyed 17 homes and flooded hundreds more. The flood ended a long argument over whether to put the wash in a concrete ditch, and voters chose parks instead. The finished Greenbelt was dedicated in 1985, and the Greenbelt entry tells that story.
What it is not
Not a canal: the Arizona Canal and the Crosscut carry irrigation water year round on a schedule, while a wash carries rain on its own schedule. Not a river, though the Salt was one before the dams. And not a safe place to stand during a storm.
The fine print
The physics are the reason for the rules. The Flood Control District of Maricopa County puts it in two numbers: six inches of moving water can sweep a person off the ground, and two feet can float a truck or SUV. Rain falling on the McDowells or the hills north of the city can send water down a wash that is dry and sunny where you stand, and dip crossings, where a road runs down through a wash instead of over it on a bridge, are the most dangerous spots because they are hard to see in the dark and can flood before anyone puts out a barricade. The Flood Control District and ABC15 list Indian Bend Wash, Cave Creek Wash, the New River crossings, Skunk Creek and the Agua Fria corridor among the Valley’s most flood-prone channels.
The law adds a bill. Arizona’s Stupid Motorist Law, ARS 28-910, enacted by the legislature in 1995, makes a driver who goes around a flood barricade onto a flooded road, and needs rescuing, liable for the cost of the emergency response, capped at $2,000 per incident. Insurers may exclude that cost, and towing and repairs are separate. The fine matters less than the message the flash flood record keeps repeating.
On foot, the rules are simpler. Do not hike a wash bed when storms are building upstream, do not wait out rain in one, and cross a running wash only when it has dropped and you can see the bottom. The Greenbelt cycling guide adds the urban version: after a monsoon storm the underpasses can hold water or silt for a day, so check before you ride.