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Stormwater: Drinking from a fire hose

Stormwater Utility Manager Mike Todnem with Town Seal

As the spring rolls into summer, residents often find themselves asking the annual question, “Are we monsoon ready?”

Wait. Is it that time already? Monsoons? Yes, we are rapidly approaching the rainy season, and as we all know, the Sonoran Desert typically sees a lot of water fall from the sky from late June through September.

May 22, 2019

A good soaking rain is almost always a good thing, but a monsoon is a potent force that illustrates just what it’s like to drink from a fire hose. Monsoons can destroy property, damage infrastructure and sadly, take lives.

So, let’s talk stormwater. Heck, I’ll even explain what a 100-year flood is and why they can happen more often than just every century or so.

Though it can be a destructive force, we also need to think of stormwater as renewable water; it’s part of an ecological cycle. And while we typically receive half our precipitation in a few summer months, the Town’s Stormwater Utility manages runoff throughout the year. Keeping drainageways and constructed washes clean and unobstructed. Preventing pollutants from entering the stormwater system. Public education projects help promote the benefits of a healthy stormwater system. All of these things are crucial.

Since the implementation of the Stormwater Utility in 2008, the Town of Oro Valley has remained diligent, taking a proactive approach that prepared the town for the active monsoon season. Street sweeping is an important aspect of stormwater preparation. Yes, it’s frustrating when you get stuck behind a street sweeper, but those vehicles are providing a necessary service by keeping pollutants out of the rainwater flowing into the storm drains.

So, it’s not an idle question to ask if we’re ready. It’s imperative that we diligently prepare, and the Town of Oro Valley works year-round to ensure its stormwater system works as effectively as it can. But it’s not just the town that has to prepare. We work hand in hand with partners, such as the Federal Emergency Management Agency, State of Arizona and Pima County.

FEMA manages floodplain issues regarding hazard identification and mapping, specifically to conduct studies and prepare flood maps. FEMA also establishes the minimum requirements for communities to adopt and apply to development with mapped flood hazard areas. They also provide federal flood insurance, which is designed to provide an alternative to disaster assistance and disaster loans for home and business owners.

The State of Arizona’s responsibility, through the Arizona Department of Water Resources, is to regulate floodplain administration, and their mission is to reduce risk to life and property by assisting local flood control and floodplain management efforts.

Pima County assists all local jurisdictions with the maintenance and monitoring of levees. The county also provides education and outreach, among other services.

The utility engages and coordinates with outside entities to find funding sources for infrastructure projects and establish procedures to help reduce the impact of severe storms, such as:

Protective road closures are set up more quickly to mitigate hazardous situations.

  • The durations of storm-related road closures are shorter.
  • Debris cleanup is more timely and responsive.
  • The amount of sediment at wash crossings has been significantly reduced.

Without knowing the severity of storms to expect, which is the biggest variable, we’re ready. But here’s the tricky part: The town’s stormwater system is built to accommodate a 100-year flood. That means the Town of Oro Valley works hard to mitigate flooding damage by planning at a 100-year storm level.   However, FEMA requires builders to build stormwater facilities to higher standards when near hospitals and senior care facilities. Simply put, probability never works out perfectly and predicting significant events is impossible. Please remember to protect your home. If you live near a wash and notice that water from that wash regularly approaches your home or business during a storm, you definitely should consider purchasing flood insurance.

Wait! You’re still wondering what a 100-year flood is.

The concept of the 100-year flood can be confusing and many people ask, “How is it possible that we can have two 100-year floods in one year?” Let’s talk about 100-year floods. Queue the drum roll, please.

A 100-year flood is just another way to define a flood that statistically has a 1 percent chance of occurring in a given year. It’s not about the time frame, it’s about the probability. And a 200-year flood has a 0.5 percent chance of occurring in a given year. A 500-year flood, a 0.2 percent chance in a given year, and so on.

Hopefully, that helps your understanding of this a little better.

Now, here’s how you can prepare for monsoon season:

Emergency kits: Put one together (

Emergency plan: Identify meeting locations and non-location emergency locations to meet, name an out-of-town contact to check in with and make sure everyone in your home is familiar with the plan

Sandbags: the town will release details on its free sandbag program in early June

And don’t forget to “Turn Around Don’t Drown.” Avoid driving your vehicle into washes when there’s flowing water present. Also be aware that the state does have what’s called the Arizona Stupid Motorist Law. Why does this law exist? Many roads which flood during monsoon season have roadblocks or barriers to keep drivers from entering. These signs and barriers must be adhered to, otherwise you could be required to pay for emergency services should you become stuck. Per Arizona State Law A.R.S 28-910, any motorist who drives past a safety roadblock into a flooded wash or channel may be liable for the expense of emergency rescue services (up to $2,000).

This law was established long before YouTube existed. Do you really want to be this year’s social media star? I didn’t think so.

By Mike Todnem, Oro Valley Stormwater Utility Manager - Explorer Newspaper, 5/22/19