Author(s): Malcolm Green; Jonathan Moores; Mike Timperley; Shane Kelly; Matthew D. Davis
Linked Author(s):
Keywords: Models; Sediments; Copper; Zinc; Harbour; Waitemata Harbour; Manukau Harbour; Auckland; New Zealand
Abstract: This paper provides an overview and sample results of two studies to predict the accumulation of sediment, zinc and copper in the Central Waitemata and Southeastern Manukau Harbours in the Auckland region, New Zealand. The study aims were to identify significant sources of contaminants, forecast their accumulation over a 100 year planning horizon and assess the efficacy of selected stormwater treatment and contaminant source control measures. The approach developed involved the application of three linked models: (1) a sediment generation model (GLEAMS), (2) an urban Contaminant Load Model (CLM) and (3) a harbour sediment/contaminant accumulation model (USC-3). The USC-3 model is underlain by other models simulating the dispersal of sediments by physical processes such as tidal currents and waves. Model development was supported by the collection of data describing physical and chemical properties of the harbour, its sediments and freshwater inputs, and by the analysis of spatial information describing catchment characteristics such as land use, topography and soil type. Sediment, zinc and copper loads estimated by GLEAMS and CLM for each subcatchment in the study area provided input data to the USC-3 model. Using hindcasted loads, the USC-3model was calibrated against sediment accumulation rates over the past 50 years and presentday zinc and copper concentrations in harbour sediments. The calibrated USC-3 model was used to predict future rates of contaminant accumulation in harbour subestuaries given variations in input loads reflecting alternative stormwater management scenarios. The predictions identify the areas within the harbour most at risk and the subcatchments where stormwater management interventions may be of greatest benefit.
Year: 2010