In 2006, Waipā Stream on the North Shore of Kaua‘i, Hawai‘i, was placed on the state's Clean Water Act Section 303(d) List of Impaired Waters after sediment and poor stream conditions damaged water quality and aquatic habitat. Dense stands of unmanaged hau bush had grown into part of the stream, trapping sediment and plant litter and making it difficult for native fish to move through the waterway, as per a report by the U.S EPA Hawaii Department of Health, Clean Water Branch.
Years of restoration work have since brought measurable changes. Average turbidity in the freshwater portion of Waipā Stream fell by 62%, while native fish populations returned to levels two to four times higher than when the project began.
