4 county-level rules, plus city-specific rules for 4 cities in Pima County, Arizona.
Verified from official government sources
Pima County enforces stormwater management through the Pima County Regional Flood Control District (RFCD) and the county MS4 permit under the Clean Water Act. The Sonoran Desert monsoon season (July-September) drives strict drainage and retention requirements. All new development must retain the first inch of stormwater on-site per county standards.
Pima County requires erosion and sediment control plans for all grading and construction activities in unincorporated areas. The Sonoran Desert landscape with sparse vegetation and intense monsoon rainfall makes erosion control critical. Grading permits through Development Services require detailed erosion mitigation before work begins.
Pima County Regional Flood Control District administers the Floodplain Management Ordinance (Title 16, Ordinance 2010-FC5). The District maps both FEMA FIRMs and local Special Study Floodplains covering more than half of known county flood hazards. FEMA updated Pima County flood maps January 2026 (appeal through April 29, 2026). Building in/near washes requires flood control approval.
Pima County requires grading permits for land disturbance in unincorporated areas and enforces strict drainage standards through the Regional Flood Control District. All new construction must demonstrate that post-development drainage does not increase runoff to adjacent properties. Washes and arroyos have mandatory setback buffers.
4 cities in Pima County have their own environmental rules rules. Each link goes to that city's dedicated page with code citations.
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Pima County Ordinance Hub →