Environmental Rules in Honolulu County, HI (2026)

5 county-level rules, plus city-specific rules for 11 cities in Honolulu County, Hawaii.

Verified from official government sources

Note: These county rules apply to unincorporated areas of Honolulu County. If you live within an incorporated city, that city's own rules apply — see the city list below.

Stormwater Management

Honolulu County regulates stormwater under ROH Chapter 43, Article 11 and Chapter 14, requiring connections to the city's separate storm sewer system and prohibiting non-stormwater discharges across all Oahu watersheds.

Oahu Stormwater and MS4 Discharge Controls

Heavy Restrictions

Full ordinance details →Official source ↗

Erosion Control

ROH Sec. 18A-1.6 requires approved erosion and sediment control plans for any building, grading, stockpiling, or trenching permit across Honolulu County, protecting Oahu's streams, reefs, and nearshore waters from construction runoff.

Erosion and Sediment Control Plans for Land Disturbance

Heavy Restrictions

Full ordinance details →Official source ↗

Coastal Development

ROH Chapter 25 implements Hawaii's coastal zone management program for all of Oahu, requiring SMA major or minor permits for development within the Special Management Area boundary that circles the island.

Special Management Areas Governed by Chapter 25

Heavy Restrictions

Full ordinance details →Official source ↗

Flood Zones

ROH Chapter 21A applies FEMA flood insurance rate maps to Oahu and requires development in special flood hazard areas to elevate to or above base flood elevation, with variances available only under strict Sec. 21A-1.12 standards.

Flood Hazard Area Development Standards

Heavy Restrictions

Full ordinance details →Official source ↗

Grading & Drainage

Honolulu County regulates grading and drainage under ROH Chapter 18A, requiring permits, bonds, and inspections for land alteration across Oahu to protect slopes, streams, and downstream properties.