In July 1994, the Hydrological Services Group was commissioned by the
Rivers Department to analyse and report on the flood hydrology for the
Waiwhetu Catchment. The study was commissioned as part of supporting
information for a proposed planning tribunal hearing over clearing of
aquatic weed using the chemical diaquat in the Waiwhetu Stream.
The intended us of the hydrological information is to develop a hydraulic
model of the Waiwhetu Stream which will then be used to route design
flows though the Waiwhetu Stream with and without the aquatic weed
within the channel. The degree of flood risk will then be evaluated from
both scenarios.