Most of Mililani Town is outside high-risk flood zones, but drainage ways and gulches fall under ROH Chapter 21A elevation and variance standards where they apply.
Chapter 21A adopts FEMA Flood Insurance Rate Maps under Sec. 21A-1.5. Much of Mililani sits on the elevated Leilehua plateau, which reduces overall flood exposure, but mapped flood zones exist along Kipapa and Waikele gulches and along other intermittent streams. Section 21A-1.8 requires structures in flood fringe areas to meet base flood elevation standards, and Sec. 21A-1.12 sets narrow conditions for variances. Residents along gulch edges, behind neighborhood drainage basins, or near Mililani's golf course drainages should verify their flood status before building additions, ADUs, or pools.
Construction below base flood elevation without a variance or without elevation certificates can void permits and complicate flood insurance.
Some links below are affiliate links — we may earn a commission if you sign up or buy, at no extra cost to you. We only recommend services we’d send a friend to.
See how other cities in Honolulu County handle flood zones.
See how Mililani Town's flood zones rules stack up against other locations.
Help us keep this page accurate. If you notice an error or outdated information, let us know.