Washes, Flash Floods and
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On a typical sunny and hot summer day in Arizona, it’s hard to worry about flood safety.
By the start of June, there isn’t a cloud in the sky and the thought of rain is but a distant memory for desert dwellers.
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| A flash flood closed the road through Madera Canyon in August 2005 |
However, sometime in late June or early July, the summer monsoon season will begin.
When exactly? No one can predict.
But one thing is certain, when the monsoons come, flash flooding will come with them.
Arizona’s monsoon thunderstorms are spectacular.
They bring much needed rain and cool the climate 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 often ignore safety warnings and cross flooded washes and roads.
They then get caught in the water and must abandon their vehicles and/or need to be rescued.
What Is a Wash?
Even very experienced Arizona drivers often forget that many of Arizona’s roads - including paved primary travel routes - cross washes. |
| The Cactus Forest Drive in Saguaro National Park’s eastern unit crosses several washes along its route |
A wash is a drainage channel rather like a dry streambed.
Washes - also known as arroyos - generally originate up in the nearby mountain ranges and act as a funnel, draining water from storms off the mountainsides.
Because washes have water at some time during the year, you’ll find plants that need more water growing along the edges of washes, like mesquite and blue palo verde trees, desert willow and desert lavender.
You can often pick out a wash from the surrounding landscape because it looks like a vibrant, green ribbon standing out from the dusty tans of the surrounding desert.
What Is a Flash Flood?
Washes remain dry for most of the year.When a summer monsoon storm blows through, so much rain can fall in such a short period of time that those normally dry washes fill with water.
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| Dry for most of the year, the Santa Cruz River in Tucson flooded with water after a powerful monsoon thunderstorm on August 23, 2005 |
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.
These events are commonly known as flash floods.
They 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.
Remember that it doesn’t have to be raining where you are for a wash or street 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 a flash flood even though not one drop of rain fell where you are.
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| Ignoring basic safety rules, this pair crosses a flooded roadway. Photo: iStockphoto |
Even large pickup trucks and SUVs 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.
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 of flash flooding and another statistic on the nightly news.
With a little precaution and common sense, you can avoid flash floods by following some simple safety tips.
Flash Flood Safety Tips
- 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.
- 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.
- 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.
- Do not allow children to play in washes.
- Avoid camping in a wash or at the bottom of a canyon with steep side slopes.
- Be extra cautious at night when it is harder to spot flash flood dangers.
Sources: City of Phoenix; National Weather Service; Pima County Sheriff’s Department; Pima County Office of Emergency Management and Homeland Security
Note to the Reader: This page is intended for informational purposes only. It is not a substitute for professional advice. This information is not meant to cover every possible scenario or outcome. Before you travel, do your homework. YOU are solely responsible for your personal safety. Road conditions, weather and your personal knowledge and abilities all vary considerably. We cannot assume responsibility for you or anyone else’s safety that reads and uses this information. Safety really comes down to common sense and being aware of your abilities and limitations. Always inquire locally before traveling. Always be conservative when planning your trips and routes.
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