Floodplain and Floodplain Use Permit FAQ

This page answers some frequently asked questions about Floodplains and Floodplain use Permits (FPUPs). It is recommended that you also review the other resources on this web site, such as the Floodplain Use Permit Guide, and other floodplain information on our Outreach page.

Note: Throughout this FAQ, the regulatory flood event will be referred to as the "base flood." The base flood is defined as a flood event that statistically has a 1 out of 100 (or one percent) chance of being equaled or exceeded on a specific watercourse in any given year. A flood event of this magnitude is often referred to (somewhat incorrectly) as a 100-year flood. A regulatory wash is a wash with a discharge of 100 cubic feet per second (cfs) or greater during the base flood or areas that are prone to sheet flooding. For more definitions of terms used within this FAQ, please see the Glossary of Flood Control Related Terms.

A Floodplain Use Permit is referred to throughout this FAQ as an FPUP.

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Do I need a permit for a culvert?

A culvert requires an FPUP if it is placed within a regulatory wash or, in most cases, within a regulatory floodplain. The District encourages the public to visit us and discuss your plans with a hydrologist, who can make the determination of whether a permit is required or not. Even if a permit is not required, the District highly recommends having the culvert designed by an Arizona registered civil engineer, as culverts that are not designed properly often do not do the job they are intended to do. Common culvert sizes convey relatively small amounts of water.

For example, a 24 inch culvert may convey 20 cfs or less. Even a non-regulatory base flood discharge of 90 cfs would require five 24 inch culverts to adequately convey the base flood. The number of culverts doesn't even take into account installing them correctly to make sure the culverts aren't damaged by erosion or to prevent downstream erosion. Improperly installed culverts could increase flood hazards to yourself and to adjacent properties, which may put you at risk of a civil lawsuit should damages occur.

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Do I need a permit for a shed or other structure which is less than 200 square feet?

All structures must be constructed in compliance with the Ordinance, but an FPUP is required only if the structure is 150 square feet or larger or if a structure less than 150 square feet in size is found to be non-compliant with the Ordinance. In order to comply with the Ordinance, ALL structures, no matter the size, must be either elevated to the Regulatory Flood Elevation or, in the case of structures used solely for the parking of vehicles and limited storage, flood-vented and flood-proofed. No structures of any size may be placed within a floodway or within an erosion hazard area unless justified by an engineering analysis. In addition, sheds must be anchored to prevent flotation or lateral movement.

Current Building Codes requirements exempt buildings less than 200 square feet. The District has a lower threshold of 150 square feet based on state and federal guidelines for structures within a floodplain.

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Do I need a permit for a wall/fence less than 5 feet high?

If the wall lies within a regulatory floodplain, an FPUP is required. While Zoning and Building Codes are concerned about the height of walls for visibility and structural reasons, it's usually the bottom 1-3 feet that have the greatest impact on flood waters. For this reason, even short walls and fences have the potential to push water onto adjacent parcels, causing increased erosion and/or flooding adjacent homes and are thus of concern to the District. Technical Policy TECH-005 (PDF format) discusses permit requirements for walls and fences in greater detail.

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Do I need a permit for an improved, concrete or asphalt, wash crossing?

If the improvement is within a regulatory wash then an FPUP is required. Improved wash crossings can be dangerous if not constructed properly. Unless the improvement is for a driveway that serves a single residence, all improved regulatory wash crossings require an engineering analysis/study, prepared by an Arizona-registered civil engineer, which demonstrates that the proposed improved crossing will be safe during the base flood and must be reviewed and approved by the District prior to issuance of any FPUP. Please visit the District to determine if the wash is regulatory.

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What is the average wait time for a permit?

FPUP processing time can vary due to workload and seasons. It is the goal of the District to respond to FPUPs within 15 working days, though turn-around times are frequently less than that. However, during the rainy (monsoon) season, wait times tend to increase.

The time it takes the District to complete a permit also depends greatly on the information that is submitted to the District. Permits can be significantly delayed if violations are found on the property, if the site plan does not adequately or accurately show proposed or existing improvements, if proposed improvements are not located appropriately in the floodplain, if the District requires additional information to properly evaluate the hazard to the proposed improvements, or if the proposed improvements are in a high hazard area.

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Do I need a permit to grade a driveway on my property?

If any portion of the proposed grading is within a regulatory floodplain an FPUP may be required. If the driveway includes any improved wash crossings (concrete, asphalt, culverts, bridge) an engineering study may be required to design the crossing so that it will withstand the base flood.

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Do I need a permit to change the direction of a wash?

Redirection or other modification of a regulatory wash requires an FPUP. In addition, an engineering analysis prepared by an Arizona-registered civil engineer must be submitted to prove that changing the wash location will not adversely affect adjacent properties. If the wash in question has a discharge of less than 100 cfs but is part of a larger floodplain a permit may be required, as the diversion may significantly adversely impact adjacent properties.

However, for any modification or redirection of a wash it is strongly recommended that the modification be designed by an Arizona-registered civil engineer to minimize the likelihood of damaging yourself or a neighbor and to avoid any civil law suits by adjacent properties as a result of your actions. Please visit the Pima County Regional District to determine if the wash is regulatory.

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How do I determine if a wash is regulatory?

To determine if a wash is regulatory, it is recommended that you visit the District’s customer service counter. In some cases, where the District is unable to determine the regulatory status, the District may request that an Arizona-registered civil engineer prepare a hydrology report to determine if the wash is regulatory.

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How high do I need to elevate my manufactured home?

The elevation requirement for manufactured homes in regulatory floodplains depends on the flood zone the manufactured home is placed in. Pima County has a variety of flood zones and each one dictates the amount of elevation necessary to protect the manufactured home. In some instances where the hazards are unknown the District may require an engineering study/analysis prepared by an Arizona-registered civil engineer to be submitted to and approved by the District prior to issuance of an FPUP. Manufactured homes must be elevated one foot above the base flood water surface elevation, as measured from the bottom of the lowest horizontal structural support member (usually the I-beam).

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How high do I need to elevate my single-family residence?

The elevation requirement for single-family residences (SFRs) in regulatory floodplains depends on the flood zone the SFR is placed in. Pima County has a variety of flood zones that require elevation of SFRs, and each one dictates the amount of elevation necessary to protect the SFR. In some instances where the hazards are unknown the Pima County Regional Flood Control District (District) may require that an engineering study/analysis, prepared by an Arizona-registered civil engineer, is submitted and reviewed prior to issuance of an FPUP. Elevation requirements for SFRs are one foot above the base flood water surface elevation measured to the lowest floor of the structure, which also includes attached garages.

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Is there a way to avoid having to elevate my detached shed or garage?

In lieu of being elevated, any fully enclosed, non-habitable structure or attached garage with a finished floor below the Regulatory Flood Elevation (RFE), which is usable solely for vehicle parking or limited storage, must be flood vented to equalize flood forces by allowing for the automatic entry and exit of floodwaters and shall be constructed of flood-proof materials up to the RFE in accordance with 44 CFR §60.3. 

Flood venting must be on at least two opposing exterior walls in the direction of flow with the bottom of the vents within one foot of grade.  The total area of flood vents must be equal to at least one square inch of venting per square foot of enclosed area. 

Flood-proof materials are those that can be inundated by floodwaters with little or no damage, such as concrete, stone, masonry, pressure-treated lumber, and epoxy paint.  See Technical Policy TECH 021 for more information. Vented and/or flood-proofed areas or structures must remain non-habitable unless brought into compliance.  The size and location of flood vents and the types of floodproof materials used must be shown on the site plan and/or building plans.

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Why do I have to complete an Elevation Certificate for my structure?

Section 16.20.070 of the Ordinance requires that for all structures within a regulatory floodplain that an Elevation Certificate must be submitted to the District for review and approval. This purpose of the Elevation Certificate is to ensure that the structure is elevated and/or flood vented as required by the FPUP for the structure. All Elevation Certificates must be completed by an Arizona-registered land surveyor or civil engineer.

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How can I determine if I am in a regulatory floodplain?

To determine the floodplain status of a property you will need to visit the Pima County Regional Flood Control District customer service counter. Floodplain information is not given over the phone.  In addition to floodplain information, District staff will also be able to give you guidance on other issues that may affect the property at our customer service counter.

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What is a local floodplain and how does it differ from FEMA floodplains?

FEMA Floodplains are mapped by the Federal Emergency Management Agency. However, there are many floodprone areas in Pima County that are not mapped by FEMA, many of them extremely hazardous. Local floodplains are mapped by or for the District to assess flood hazards affecting the citizens of Pima County. To determine the floodplain status of a property you will need to visit the District's customer service counter.

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If I have a wash on my property how far do structures need to be away from it?

Wash setbacks, also known as erosion hazard setbacks, depend upon the base flood peak discharge (flow rate) going through the wash at the property. For regulatory washes, the setback can range from 25 feet to 500 feet. In some cases the District may be unable to determine the base flood discharge of the wash and may require that a engineering analysis/study, prepared by an Arizona-registered civil engineer, be submitted to and reviewed by the District prior to issuance of an FPUP. Please visit the District to determine what erosion hazard setback distance, if any, is required.

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How do I obtain an Elevation Certificate for my Mortgage/Insurance company?

If the Pima County Regional Flood Control District has a completed Elevation Certificate on file for your structure, you can view and print it from our Elevation Certificate Listing page. If you can’t find the Elevation Certificate on the web site then it will be necessary for you to hire an Arizona-registered land surveyor to complete a new Elevation Certificate form. You may also visit the District customer service desk to obtain a blank Elevation Certificate. More information is available on the Elevation Certificate page and the flood insurance page.

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Do I need a permit to replace a manufactured home on my property?

Yes, any time a manufactured home is replaced within a regulatory floodplain a new FPUP is required. This is to ensure that the new manufactured home will be set in compliance with the current Ordinance.

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My neighbor is blocking/altering a wash or floodplain. Who should I contact?

If a neighbor is blocking or altering a wash or regulatory floodplain it may constitute a violation of the Ordinance and may cause adverse affects to adjacent properties. As such, the District should be contacted. Please read the Drainage Complaints page for more information about drainage complaints.

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My house was flooded during a storm event. Should I contact the Regional Flood Control District?

If the house was flooded during a storm event you should contact the District. A representative of the District will contact you and/or visit the site to review the cause of the flooding and to provide recommendation on how to remediate the damage to the structure and can provide advice for protecting the structure from future flood events. The structure may experience mold problems if proper steps are not taken to dry out any moisture. In addition, repairs to the structure may require an FPUP.

Other than providing advice, the District is limited in the amount of other assistance, including financial assistance, which can be provided. The District is prohibited from spending public money on private property.