Charles Cotton, thank you for raising with me your concern regarding the amount of weed growth in the Orphanage Stream. 
Charles, I am advised that there are two main pest plants - Vietnamese Parsley (Oenanthe javanica) and Water Celery (Apium nodiflorum) that are affecting our streams in the Stoke area. Both plants grow rapidly & regenerate by rooting from very small, detached fragments and/or seed.
You will be pleased to learn that NCC’s Biosecurity & Parks teams share your concern & are working together with urgency around the appropriate management of these two invasive aquatic pest plants.
NCC is developing a range of management options for dealing with these plants. It is likely that any management of the weeds will incorporate levels of mechanical/physical removal, as well as agrichemical management to deliver effective & efficient control. 
Council contractors are presently trialling hand removal of the weeds in the affected waterways, such as Orphanage Stream at Saxton Road, Saxton Creek at Ngati Rarua Street.