Honolulu Vegetated Swale Requirements

This Honolulu Ordinance defines vegetated swales (or grass swales) as shallow, plant-lined channels for runoff conveyance. It requires that they have side slopes no steeper than 3:1 (unless otherwise approved), a bottom width ≤10 feet, water depth ≤4 inches, flow velocity ≤1 ft/sec, and a minimum 7-minute residence time.