A powerful urban planning tool
An innovative model that predicts long-term accumulation of contaminants in estuaries, including heavy metals, pesticides and hydrocarbons, is proving a powerful tool for planning development around the sensitive Upper Waitemata Harbour.
NIWA’s USC-2 (Urban Stormwater Contaminant) model can predict the likely environmental effects of different planning options in a timely and cost-effective way.
The model has highlighted some tricky tradeoffs. For example, the largest supplier of zinc to the middle main body of the harbour is the heavily urbanised Lucas subcatchment, but this also supplies a significant sediment load which dilutes contaminants.
‘The way forward’, says NIWA principal scientist Dr Malcolm Green, ‘is to run the model in a kind of iteration, with scientists and planners discussing results after each loop until an acceptable development strategy can be found. In the case of the Upper Waitemata Harbour, stormwater treatment alone may not deliver acceptable environmental outcomes in some critical parts of the harbour, which points at the need to control generation of contaminants at source. The USC-2 model is providing planners with the information they need to develop, and defend, their policies.’
The work has been funded by the ARC, Transit NZ, North Shore City Council, Waitakere City Council, Rodney District Council, and the Foundation for Research, Science & Technology