Flood Control District
The Flood Control District of Maricopa County works to reduce flood risk to people and property throughout the county. Residents, property owners, builders, engineers, businesses, and public agencies may interact with the District when checking floodplain status, reviewing flood maps, planning development, applying for floodplain or right-of-way permits, researching drainage studies, following flood-control projects, reviewing rainfall data, or reporting a problem. This article explains the District’s responsibilities, the official systems available to the public, the information to review before beginning a project, and common mistakes that can delay or complicate flood-related work.
District Role and Responsibilities
The Flood Control District of Maricopa County was created in 1959 to reduce the risk of flooding to people and property. Its mission includes minimizing property damage and loss of life, supporting economic development in a safe manner, and recognizing stormwater as a resource that can benefit the community and environment over the long term.
The District’s work extends well beyond responding to individual flooding concerns. It plans, designs, constructs, operates, and maintains flood-control facilities and also uses floodplain regulation, engineering studies, mapping, public education, technical resources, and partnerships with local agencies to reduce risk. The county’s official Flood Control District page serves as a central starting point for projects and studies, floodplain regulations, District programs, technical information, business resources, and common public requests.
Historically, much of the District’s work has involved dams, basins, channels, and similar flood-control infrastructure. The agency also uses modern flood-risk mapping, rainfall monitoring, drainage studies, engineering tools, and educational programs to address changing development patterns and flood hazards across Maricopa County.
District Governance
The District is governed by a five-member Board of Directors. The same elected officials also serve as the Maricopa County Board of Supervisors. The Board of Directors exercises authority involving District property, contracts, regulatory functions, and other matters normally handled by a governing body.
The Flood Control Advisory Board serves in an advisory role on flood control, drainage, floodplain management, and related matters. Its work includes reviewing planning, operations, and maintenance of flood-control facilities and recommending an annual budget that includes a five-year Capital Improvement Program.
Floodplain Status and Mapping
One of the most common reasons to contact the District is to determine whether a home, parcel, business, or proposed project is within a designated floodplain. The county provides an official GIS Floodplain Viewer and other mapping resources for this purpose. The Floodplain Information page explains how designated floodplains are identified and provides access to information about floodplain determinations and Flood Insurance Rate Maps.
Floodplain information is particularly important before construction, grading, filling, fencing, or other physical changes to property. A project that appears minor may still require District review if it is located within a designated floodplain.
Floodplain Management Jurisdiction
The Flood Control District is responsible for floodplain management and regulation in unincorporated Maricopa County. It also performs floodplain management functions in certain incorporated communities:
Buckeye
Carefree
Cave Creek
Chandler
El Mirage
Gila Bend
Guadalupe
Litchfield Park
Mesa
Queen Creek
Surprise
Tolleson
Wickenburg
Youngtown
Other municipalities conduct their own floodplain management. These include Avondale, Fountain Hills, Gilbert, Glendale, Goodyear, Paradise Valley, Peoria, Phoenix, Scottsdale, and Tempe. Property owners in those jurisdictions should direct floodplain questions to the appropriate city or town rather than assuming the Flood Control District is the permitting or regulatory authority.
This distinction matters because flood-related mapping and studies may cover a large geographic area, while responsibility for approving development or answering a parcel-specific regulatory question may belong to a municipality. Confirming the governing floodplain agency early can prevent applications from being submitted to the wrong office.
County Mapping Tools
The District provides several mapping products for different purposes. The county’s Flood Control online maps include current and pending 100-year FEMA effective floodplain maps, current and historical aerial photography, flood hazard identification studies, a Flood Control Projects Map, a floodplain and elevation certificate viewer, and structures and property information.
Different maps should not be treated as interchangeable. A map designed to display engineering model results does not necessarily establish the official regulatory floodplain for a property. Users should pay attention to the stated purpose of each map before relying on it for a permit, development decision, or floodplain question.
FLO-2D Limitations
The FLO-2D Web Access Tool is intended primarily for experienced engineers. It can assist with site drainage and grading plans and with evaluating proposed lowest-floor elevations for new structures. The tool presents modeling results from Area Drainage Master Studies and Plans and Floodplain Delineation Studies, including estimated peak discharges, dominant flow directions, and peak water-surface elevations.
The District specifically states that the FLO-2D map is not an official document for making a floodplain determination. Treating model-output data as an official floodplain designation is a significant mistake. Users applying the data for the first time are encouraged by the District to consult District staff or the appropriate governing agency to understand the basis and appropriate use of the information.
Floodplain and Right-of-Way Permits
The District issues permits for certain development activities affecting floodplains and District property. The Flood Control District permits page separates two major permit types that applicants should understand before beginning work.
Floodplain Use Permits
A Floodplain Use Permit is required for development within a designated floodplain. The requirement is broader than major building construction. According to the District, a permit must be obtained before building, grading, filling, installing walls or fencing, or making other man-made changes to property within a designated floodplain.
The permit requirement also applies to extraction of sand, gravel, or other material from a floodplain. A person should not assume that the absence of a building-permit requirement means no Flood Control District permit is needed. Floodplain regulation applies independently to covered work within a designated floodplain.
Before planning construction or site work, determine the floodplain status of the property and identify which agency has floodplain-management jurisdiction. If the District is the responsible agency, review its permit information before work begins rather than waiting until grading or construction is underway.
Right-of-Way Use Permits
A Right-of-Way Use Permit applies when development or access is requested on property the District owns, on property over which the District holds an easement, or on structures maintained by the District. This is different from a Floodplain Use Permit. The first concerns District property, easements, or maintained structures, while the second concerns development within designated floodplains.
A project can involve different regulatory issues at the same time, so identifying the physical location of the work, the applicable floodplain designation, and any District property or easement interests is an important early step.
Permit Payment Safety
Maricopa County states that it will never request permit payment by wire transfer. Permit payments are made exclusively through the County Permit Center, where applicants can review and verify invoicing information. The County also states that it will not solicit passwords or other confidential login information.
Requests for wire transfers or confidential credentials by telephone, email, or another communication method should not be treated as legitimate permit instructions. Applicants should verify questionable communications directly with Maricopa County before making a payment or releasing account information.
Projects and Drainage Studies
The District maintains an online system covering active and completed flood-control projects and studies. The Flood Control District projects system allows residents and other users to review projects by name and project type.
Active work can include construction, engineering and design, floodplain delineation studies, drainage master studies, rehabilitation work, drainage improvements, and modifications to dams or other facilities. Examples shown in the District system include projects involving Cave Buttes Dam, McMicken Dam, the East Maricopa Floodway, Gila Bend drainage improvements, Rawhide Wash, Sun City West drainage improvements, and several area drainage master studies.
The project system also lists completed work. Users looking for documents associated with completed projects and studies are directed to the Flood Control District Library. Searching by the formal project or study name is useful because project titles often identify a specific drainage area, roadway, wash, dam, flood-retarding structure, or study boundary.
Why Project Type Matters
A study and a construction project should not be confused. An Area Drainage Master Study, Floodplain Delineation Study, or similar planning effort may evaluate flood hazards and model drainage conditions without immediately constructing improvements. Engineering and design projects may be preparing future construction documents. Construction projects involve physical improvements or rehabilitation.
Understanding this distinction can help a resident interpret what an online project listing means for a nearby property. A study may generate maps, models, recommendations, or future project concepts, while an active construction project represents a different stage of District work.
Rainfall and Storm Information
The District operates an extensive rainfall monitoring network. Its official rainfall data page states that 378 automated precipitation gages are installed and maintained throughout Maricopa and surrounding counties. The gages measure the amount and timing of rainfall and transmit data by radio to District computer systems.
Public data products include real-time and historical information in tables, maps, plots, and downloadable reports. Available reports include daily precipitation totals, six-hour and 24-hour totals, and rainfall values for 15-minute, one-hour, three-hour, six-hour, 24-hour, and 72-hour periods.
Historical products include daily totals going back to October 2010, past contoured rainfall maps by storm date, annual and monsoon rainfall total maps, maximum recorded rainfall amounts for selected durations, and rainfall history documents.
These products can help users understand where rain has fallen and how rainfall varies across the county. They should not be confused with an official determination that a particular property is or is not within a regulated floodplain.
Flood Insurance Considerations
Floodplain status and flood insurance are related but are not the same question. Maricopa County states that flood damage is not typically covered by homeowners insurance and that separate flood insurance can be purchased. A mortgage company may require flood insurance when a property is in a floodplain, but coverage may also be purchased for property outside a designated flood zone.
The county’s Flood Insurance information page also explains that flood insurance generally has a 30-day waiting period between purchase and the effective date of coverage. Waiting until a storm appears in the forecast can therefore be too late for a new policy to take effect.
The Flood Control District participates in the National Flood Insurance Program’s Community Rating System. The program recognizes communities that undertake floodplain-management activities exceeding federal minimum requirements. Property owners should use current official insurance and floodplain information when evaluating their circumstances rather than assuming that a floodplain map alone answers all insurance questions.
Programs for Flood Reduction
The District administers several programs involving public agencies, localized flood-control improvements, flood-prone properties, education, and community floodplain management. The District Programs page explains the scope and eligibility of these programs.
Capital Improvement Program
Capital Improvement Program projects generally involve the design and construction of flood-control infrastructure. Eligible project types may include new infrastructure identified in a District plan or study, certain rehabilitation projects, road-drainage improvements that address flooding restricting access to specified critical facilities, and bridges or other watercourse crossings that are impassable to emergency vehicles.
Eligibility does not guarantee District funding. For a project to be included in the District’s annual Capital Improvement Program budget, an Intergovernmental Agreement must be in place and approved by the Board of Directors. The agreement must address project background and objectives, estimated costs, cost sharing, and responsibility for operations and maintenance.
This program is structured around agency partnerships rather than ordinary individual homeowner applications. Agencies may submit project-eligibility proposals through the District’s online Partnership Application at any time.
Small Project Assistance Program
The Small Project Assistance Program is designed for smaller and more localized flood-control projects that can move through design and construction relatively quickly. The program uses eligibility criteria and a scoring matrix, relies on standard intergovernmental agreements, and expects projects to be completed within two years or less.
The District contribution is limited to 75 percent of eligible design and construction costs for flood-control elements, with a maximum District contribution of $1 million. Property acquisition, utility relocation, permitting, construction management, materials testing, survey work, and operations and maintenance remain the participating agency’s responsibility.
A proposed project must score at least 40 points under the scoring matrix to be considered. Factors include addressing frequent localized flooding, road flooding that restricts access to critical facilities, the level of project design, and whether the agency has property rights in place.
Floodprone Property Assistance
The Floodprone Property Assistance Program addresses flood hazards where constructing flood-control structures is impractical. Homeowners living within delineated floodplains may apply for assistance. Eligible homeowners may qualify for a voluntary sale to the District at appraised market value and, under certain circumstances, moving-expense assistance.
Homes acquired by the District through the program are demolished, and the property remains open so the floodplain can return to its natural function. Because this is a specific mitigation program, homeowners should review the program criteria rather than assuming that every property within a floodplain is eligible for purchase.
Engineering and Technical Materials
Engineers, contractors, consultants, and agencies working on drainage and flood-control projects can access District design manuals, standards, procedures, software, modeling tools, and technical publications through the Doing Business With the District page.
Published technical materials include drainage design manuals covering hydrology, hydraulics, and erosion, as well as the Drainage Policies and Standards Manual, standard details, and other engineering resources. The District also provides software that may be used for hydrologic, hydraulic, and river-mechanics modeling associated with permit applications, floodplain studies, drainage master studies, watercourse studies, and capital projects.
The Drainage Design Management System is a Windows-based tool originally developed as a preprocessing tool for HEC-1 modeling. Later functions include storm-drainage hydraulics and river mechanics. Other technical tools include the HEC-1 cumulative drainage-area calculation tool and resources supporting customized HEC-HMS features used in Maricopa County.
These technical resources are specialized engineering materials. Public availability does not mean every tool is suitable for determining the regulatory status of a parcel. Users should distinguish engineering design aids from official floodplain determinations and permit decisions.
Reporting Problems and Complaints
Maricopa County provides an online Service Request Access system for reporting non-emergency issues. The system can be used to create a new request, view existing requests, and, where agency access permits, view requests in a neighborhood. Users may register or sign in to track requests they submit.
The service-request system is specifically identified as a non-emergency service. Emergency situations should be handled through 911 rather than through an online county request.
Nondiscrimination Complaints
The Flood Control District also maintains a separate nondiscrimination complaint process for allegations involving District programs, activities, or services. A person who believes discrimination occurred may first contact the District’s Nondiscrimination Program Coordinator in an effort to seek an informal resolution.
If the matter cannot be resolved informally, a written or verbal complaint may be submitted within 180 days of the alleged discrimination. The complaint must include:
The complainant’s name.
The nature of the complaint.
The dates associated with the complaint.
The action being requested.
Contact information.
The coordinator may request additional information. If requested information is not provided, the case may be closed. A case may also be closed if the complainant no longer wants to pursue it.
If the complaint falls within District jurisdiction and cannot be resolved informally, it is investigated. The District states that its goal is to address complaints within 60 days after receipt, although a more complex matter may require additional time. The complainant is notified in writing of the investigation results, actions taken or planned, and the timeline for requesting review.
Common Flood Control Mistakes
Many avoidable problems begin with using the wrong agency, map, permit, or payment method. Before relying on flood-control information or beginning physical work, keep the following distinctions in mind:
Do not assume the District regulates every incorporated city. Several cities and towns administer their own floodplain programs.
Do not treat every engineering map as an official floodplain determination. The FLO-2D tool is an engineering aid and is specifically identified as unsuitable for making an official floodplain determination.
Do not assume a building permit is the only approval required. Work within a designated floodplain may require a Floodplain Use Permit even when a building permit is not needed.
Do not confuse a Floodplain Use Permit with a Right-of-Way Use Permit. They address different circumstances and property interests.
Do not begin grading, filling, fencing, or similar work in a designated floodplain before determining permit requirements.
Do not send permit payments by wire transfer. Maricopa County states that legitimate permit payments are processed through the Permit Center.
Do not provide passwords in response to an unsolicited county payment or permit message. The County states that it does not request confidential login credentials.
Do not confuse rainfall measurements with regulatory floodplain status. Rainfall reports describe precipitation, while floodplain maps and regulatory determinations address a different question.
Do not use the county service-request portal for emergencies. Emergency situations require 911.
Flood Control District Office
Flood Control District of Maricopa County
2801 W. Durango Street
Phoenix, AZ 85009
602-506-1501
Flood Control District FAQs
Where can I check the District’s latest weather outlook?
Maricopa County publishes a District weather outlook that focuses on conditions affecting the county, including expected rainfall, thunderstorm potential, atmospheric moisture, temperatures, and changing storm patterns. The page also links to rainfall maps and provides rainfall and thunderstorm outlook information. Because forecasts are updated as conditions change, residents concerned about monsoon storms or approaching weather should review the official Maricopa County Weather Outlook rather than relying on an older forecast.
Does the District provide flood education materials for schools?
Yes. The District offers free STEM curriculum for educators serving grades K-8. The lessons support Earth’s water standards and were developed to align with Arizona Science Standards. The materials are intended to help students learn about water, flooding, and related science topics in a classroom setting. Educators can find information about the curriculum through the District Programs page, which identifies the STEM curriculum as one of the District’s public programs.
Has Maricopa County changed its flood-control permitting process?
The District has been working on permitting improvements with representatives from engineering firms, builders, contractors, utilities, attorneys, and other industry groups. A permitting task force held 12 meetings and developed 18 recommendations intended to streamline the process. According to the county’s published information, nine recommendations had been implemented as of May 2024. The work included separate subcommittees addressing sand-and-gravel Floodplain Use Permits and community Floodplain Use Permits. Applicants working on projects that may require District approval can review the latest permitting and task-force information on the official About the District page, since procedures may continue to change as additional recommendations are implemented.