Arizona’s dry desert climate can give property owners a false sense of security when it comes to water management. Tucson and the surrounding region receive most of their annual rainfall in a compressed monsoon window from July through September, and when those storms hit, they hit hard.
A properly designed and installed storm drainage system is what stands between a functioning property and one that floods, erodes, or fails its foundation.
What Is a Storm Drainage System?
A storm drainage system is a network of inlets, pipes, channels, retention basins, and drainage structures designed to collect and redirect rainfall runoff away from buildings, paved surfaces, and vulnerable infrastructure. Unlike sanitary sewer systems that carry wastewater to treatment facilities, storm drainage systems handle precipitation only, moving water where it needs to go so it doesn’t cause damage where it lands.
Storm drainage infrastructure ranges from simple swales graded into a landscaped area to engineered underground pipe systems capable of handling thousands of gallons per minute during heavy rainfall events. The scale and complexity of the system depend on the size of the property, its location, the amount of impervious surface area, and local jurisdiction requirements.
Why Is Storm Drainage Particularly Important in Southern Arizona?
Southern Arizona experiences what hydrologists call high-intensity, short-duration rainfall. Monsoon storms can drop over an inch of rain in less than an hour, which is more than many other regions receive in a month.
The ground, which has been baked dry and hardened by summer heat, cannot absorb water at that rate. Runoff is rapid and, without a proper storm drainage system, it has nowhere to go but across parking lots, into buildings, and along roadways.
The National Weather Service’s Arizona Flash Flood Awareness page documents flash flooding as the number one weather-related cause of death in Arizona. The combination of desert terrain, intense monsoon precipitation, and properties that weren’t built with adequate drainage creates serious hazards every storm season. A properly designed storm drainage system manages these conditions before they become dangerous.
What Are the Main Components of a Storm Drainage System?
Storm drainage systems are made up of several interconnected components, each serving a specific function:
Catch Basins and Inlets
These are the collection points where surface water enters the underground pipe system. They’re positioned at low points in parking lots, along curb lines, and at other areas where runoff naturally accumulates.
Underground Storm Drain Pipes
Reinforced concrete or high-density polyethylene (HDPE) pipes carry collected water from inlets to discharge or retention points. Pipe sizing is calculated based on the drainage area and expected rainfall intensity.
Retention Basins
Common throughout Pima County and Tucson, retention basins hold storm water on-site and allow it to slowly percolate into the ground. Many commercial and industrial developments are required to retain a certain volume of runoff before any water can discharge off-site.
Detention Basins
Similar to retention basins but designed to temporarily hold water and release it slowly into the drainage system rather than retain it indefinitely. These are used when full retention isn’t feasible due to soil conditions.
Concrete Channels and Swales
Open channels lined with concrete or rip-rap direct surface water to collection points or discharge areas. They’re often used along property boundaries and in areas with high runoff velocity.
How Are Storm Drainage Systems Designed for Arizona Properties?
Storm drainage design in Arizona follows standards published by the Pima County Regional Flood Control District. The district’s Hydrology Manual outlines how engineers calculate runoff volumes and size drainage infrastructure for both 10-year and 100-year storm events.
Properties with large impervious surfaces, including parking lots, rooftops, and driveways, generate significantly more runoff than undeveloped land, and the design must account for that difference.
From those calculations, engineers size the pipes, basins, and inlets needed to handle peak flow. ADOT’s Drainage Design Manual also influences drainage requirements for both public infrastructure and private development throughout Arizona.
Once the design is approved, installation becomes a civil construction project. Our team works from engineered drainage plans, installing underground pipe runs, forming and pouring concrete structures, and grading retention basins to specified depths and slopes.
What Happens When Storm Drainage Is Inadequate?
Properties without adequate storm drainage face a range of problems that compound over time. Ponding water accelerates asphalt deterioration, undermines subgrade stability, and creates safety hazards for pedestrians and drivers.
The Federal Highway Administration’s Pavement Distress Identification Manual identifies water infiltration beneath paved surfaces as one of the leading causes of premature pavement failure across the United States.
Beyond pavement damage, standing water near building foundations creates hydrostatic pressure that can crack concrete slabs and footings. In desert soils, where expansive clay content is common, repeated wet-dry cycles cause significant soil movement that damages structures over time.
Buildings in low-lying areas without proper drainage are also at risk of interior flooding, which creates mold and structural repair costs that far exceed what a well-designed drainage system would have cost.
What Are the Regulatory Requirements for Storm Drainage in Southern Arizona?
Most commercial development in Southern Arizona requires storm drainage plans approved by the local jurisdiction before a grading permit is issued. In Pima County, the Flood Control District reviews drainage reports for developments that could affect downstream water flow. The City of Tucson has its own drainage review process through its Development Services Department.
Projects that disturb more than one acre of land are also subject to federal stormwater permitting requirements under the Clean Water Act. In Arizona, these are administered through the AZPDES Construction General Permit, which requires a Stormwater Pollution Prevention Plan outlining erosion and sediment controls during construction. Learn more about how we handle civil construction permitting and site work.
How Does Storm Drainage Connect to Paving and Site Development?
Storm drainage installation happens during site preparation, before paving or concrete flatwork begins. This is intentional: underground pipe runs, inlet box forms, and retention basin shaping all have to be in place and correctly graded before any surface work covers them. Once the drainage infrastructure is buried and the subgrade is compacted, paving can begin.
The connection between drainage and pavement longevity is direct. A parking lot or access road that sheds water efficiently and keeps moisture out of the subgrade will last significantly longer than one that holds water or allows it to infiltrate beneath the surface.
Our team installs storm drainage systems as part of complete site development packages that include grading, drainage, and paving. Visit our services page to see the full scope of what we offer.
Protect Your Southern Arizona Property With the Right Storm Drainage System
Storm drainage isn’t a secondary concern for Arizona property owners; it’s one of the most important investments a site can have.
Properly designed and installed systems protect pavement, foundations, landscaping, and the people who use your property every day. When storm drainage is overlooked or undersized, the repair costs during and after monsoon season make the original investment look very reasonable.
We design and install storm drainage systems for commercial, industrial, and residential properties throughout Southern Arizona. If you’re planning a development or dealing with drainage problems on an existing site, we can help. Reach out to our team to discuss your drainage needs.
