Floodplain Management Plan
Sound floodplain management plays a critical role in the success of the Pima County Regional Flood Control District's core mission and the well-being of Pima County. To this end, the District has worked with stakeholders and the public to create a comprehensive Floodplain Management Plan for unincorporated Pima County.
District Responsibilities
The District has a long-standing history of utilizing non-structural approaches to floodplain management wherever possible. To this end, the District is responsible for the following:
Natural and Beneficial Functions of Floodplains
Floodplains are a combination of water, geology and vegetation that are typically both dynamic and stable. Individual floods may remove or deposit sediment, cause channels to migrate, and destroy or benefit vegetation, but in the long term natural floodplain systems do not vary much over time. Even when initiated by good intentions, human modification of and intervention in floodplain systems often create an imbalance in the system that can have far reaching, unintended negative consequences. So-called "fixes" often just push the problem further downstream, which may require the expenditure of even more resources to fix.
For these reasons, maintaining the flood and erosion control functions of natural floodplains is crucial. Pima County's mountainous terrain and often impervious soil prevent rainfall runoff from quickly soaking into the ground, thus creating flash floods in typically dry washes both during and after severe rainfall events. Floodplains naturally contain and store this runoff until it is absorbed into the soil to replenish our precious groundwater supply. Best of all, floodplains provide this service to us for free! All we have to do is protect them.
Natural and beneficial functions of floodplains include:
- Stormwater/floodwater control
- erosion control
- water purification and groundwater recharge
- providing habitats which support a wide variety of plant, wildlife and fish species
- recreational opportunities for parks, walking/biking paths, open space and wildlife conservation
The Floodplain Ordinance and associated rules help keep floodplains clear to function as nature intended by establishing development restrictions and permitting requirements necessary to protect the beneficial functions of floodplains.
Pima County's washes are typically ephemeral, meaning they do not contain water year-round. This makes their beneficial functions less obvious . . . until that flood does come. Often our floodplains do not stay flooded for long, sometimes for less than an hour. However, protecting small streams reduces flood volumes and the destructive force of floods downstream, meaning people, homes, and infrastructure are safer. Protecting streams also means that less tax dollars need to be spent constructing improvements to improve flood safety.
Larger floodplains in the county that may flood for days. It is these larger floodplains, when they are in Pima County's more urban environments, that most often need human enhancement to mitigate the impacts of flooding on existing development. Just one example of this is the award winning Arroyo Chico Multi-Use Project which provides the Tucson metropolitan area with flood protection in wet weather while also providing amenities such as multi-use paths and soccer and baseball fields in dry weather.
Of equal importance to these large-scale structural enhancements of floodplains are the protections given to floodplains large and small throughout Pima County. The floodplains of the major watercourses in Pima County are especially important. In addition to their natural floodwater control properties, they provide wildlife habitat, and groundwater filtering and recharge. Floodplains can lose their ability to provide beneficial functions due human alteration. The District protects and enhances flood resilience within Pima County by acquiring and preserving natural floodplains and also by restoring damaged floodplains. One way that the District acquires land within floodplains is through the Floodprone Land Acquisition Program (FLAP). Lands acquired by the District may be managed passively if they are near natural state or may be actively restored if the land has lost some of it's beneficial floodplain function. Restoration efforts such as the Big Wash Rehabilitation Project and the Pantano Jungle Restoration Project can bring a floodplain back to its original state.
Floodplain Delineation
The District conducts floodplain delineation studies for 100-year floodplains throughout the County. Floodplain delineation involves the development of detailed topographic maps to determine where water flows, while incorporating the results of rainfall runoff relationship studies to determine peak flood discharges and depths. Along with extensive surveying and aerial mapping, drainage factors such as slope, vegetation, soil composition and land use are also analyzed and taken into account.
The delineation studies are used by the District to better manage the floodplain, to reduce or prevent flood damage, and to maintain the natural and beneficial functions of the floodplains. The studies may also be used to update FEMAs Flood Insurance Rate Maps (FIRMs), which support the function of the National Flood Insurance Program.
Flood Insurance Information
If your property is located in a FEMA Special Flood Hazard Area (SFHA) and there is a federally-backed loan on the property, you are required by your lender to purchase flood insurance. Please see the Flood Insurance Page for more information. Residents of unincorporated Pima County are encouraged to submit a Flood Hazard Information Sheet to the District to determine whether or not their property is in an SFHA, and to obtain a Flood Hazard Map for their property to determine if they are in a locally mapped floodplain. If you do need flood insurance, you will need an Elevation Certificate for the structure. The District may have a completed Elevation Certificate on file for your property. There are alternatives to purchasing flood insurance. It may be possible to obtain a Letter of Map Revision or make changes to your house or property that could move you out of the regulatory floodplain.
Floodplain Use Permits
Any development or activity within a regulatory floodplain will likely require a Floodplain Use Permit (FPUP). The District enforces floodplain regulations, which regulate the location and construction of buildings and other development within designated floodplains. The District is required to ensure improvements in the floodplain will not cause adverse impacts to neighboring properties. Please visit our Permitting page for more information.
The ALERT System and Flood Warning
The District maintains an extensive system of rainfall and stream gages throughout eastern Pima County. This system, called Automated Local Evaluation in Real Time (ALERT) system, relays critical precipitation and stream flow information to the District in real time. This data is used by the National Weather Service to provide flood warnings to the public. These warnings can be found on the National Weather Service Severe Weather Summary Page. Floodwaters can rise very quickly so it is important to be prepared for flooding before it occurs.