Washes, Flash Floods and
Flash Flood Safety Tips

One thing, however, is certain. When the monsoons come, flash floods will come with them.

Arizona's monsoon thunderstorms are spectacular.

They bring much needed rain and cool the temperatures just when it's getting hottest.

But when all of that rain falls in a short period of time, flash flooding often results.

Unfortunately, motorists and pedestrians often ignore safety warnings and cross flooded washes and roads.

A flash flood closed the road through Madera Canyon in August 2005

A wash is a drainage channel rather like a dry stream bed. They generally remain dry for most of the year.

Washes - also known as arroyos - usually originate up in the nearby mountain ranges and act as a funnel, draining water from storms off the mountain sides.

Because washes have water at some time during the year, you'll generally see plants that need more water growing along the edges of washes, such as mesquite and blue palo verde trees, desert willow, and desert lavender.

However, the two primary causes are how much rain falls and how long it lasts.

When a summer monsoon storm blows through, so much rain can fall in such a short period of time that those normally dry washes, as well other low lying areas such as fields and roads, fill with water.

In just a few minutes, the sandy ground turns into a roaring, frothy wall of water, mud, tree limbs, giant boulders, plant debris, gravel, and anything else caught in the water's rush.

Dry for most of the year, the Santa Cruz River in Tucson flooded with water after a powerful monsoon thunderstorm on August 23, 2005

Flash floods are so powerful that they can literally destroy everything in their path.

Desert areas are very susceptible to flooding because the hard, dry desert soil doesn't allow rains to soak in before the water moves across the dry ground.

Flash floods don't just happen in the desert, however. They can occur in burned areas after forest fires, after a dam or levee break, or when water is suddenly released from an ice jam.

Sometimes they occur due to a very slow moving thunderstorm, or from storms that repeatedly move over the same area, or from the heavy rains caused by tropical storms and hurricanes.

Remember that it doesn't have to be raining where you are for a wash or roadway to become flooded.

Washes originate up in the mountains, miles away, where it may be storming even though it is dry and sunny down on the desert floor.

Within a short period of time, the water falling on those mountains will be racing down the washes.

You could be caught in rapidly rising water even though not one drop of rain fell where you are.

Even large pickup trucks and SUVs can get stuck or swept away.

Remember:

• The strength of the flow is the critical force, not the depth of the water.
• As little as 10 inches of water can float average-size cars and trucks.
• Control of a vehicle is lost in 6 inches of water.
• Flash flooding usually occurs within 6 hours of a rain event.

To learn about what it's like to be caught in powerful Arizona flash floods, read author Craig Childs' highly compelling and beautifully written book The Desert Cries.

His re-telling of the dramatic and tragic events that occurred over several parts of the state in September 1997 is a story you won't soon forget.

Over 107 people have been killed in Arizona flash floods and many more have had to be rescued.

But no one needs to be a victim and another statistic on the nightly news.

With a little precaution and common sense, you can stay safe by following some simple flash flood safety tips.

• Listen to the weather forecasts for flash flooding advisories, watches, and warnings as well as urban and small stream advisories.
• Pay attention to environmental cues when you're outside: listen for distant thunder and watch for rapidly rising water.
• Always be careful when approaching a wash, even if it's not raining where you are. A wash can become flooded by a thunderstorm that is occurring several miles away.
• If you're out hiking or walking and flooding begins, get to higher ground as quickly as you can.
• Do not allow children to play in washes.
• Avoid camping in a wash or at the bottom of a canyon with steep sided slopes.
• Be extra cautious at night when it is harder to spot water dangers.
• If a wash or roadway is flooded, do not cross it, even if it is not barricaded. Turn around and take an alternate route. Or, wait until the water recedes. The waters generally take an hour or so to drop.
• Remember the Arizona "Stupid Motorist" Law: a motorist who drives onto a flooded public road or highway, or a wash that is barricaded due to flooding is liable for the costs of any emergency response required to rescue the driver, any passengers and for removal of the inoperable vehicle.
• Heed all warning signs. If a sign says Do Not Enter When Flooded, don't enter.
• Do not drive around barricades. Not only is it illegal, it could cost you your life or the life of someone you love.
• Stay away from roads that appear flooded, even if there are no warning signs.
• In the event that you or someone else is trapped in water, call 911.
• If you are caught in a flooded wash or roadway, try to climb out onto the roof of your vehicle. Call 911 and wait for help.
• If the water is still low and you can wade to safety, do so, but be careful of floating debris.

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