Auckland in New Zealand has the most densely populated coast in the country and is facing a series of major challenges, including rapid growth, against a backdrop of declining coastal water quality. Biodiversity, cultural values, fisheries and broader ecosystem services are at risk of degradation while simultaneously benefiting from investment as Auckland grows. Through a contaminant assessment using an integrated model from DHI and Auckland Council, as well as by implementing an online Coastal Receiving Environment Scenario Tool, the city can now better evaluate and predict implications to coastal water quality.

 

Auckland Council’s Freshwater Management Tool FWMT predicts water quality and flows in each of the region’s catchments, however, the tool does not simulate outcomes in estuaries or harbours, creating uncertainty about current and future effects on Auckland’s coast. This makes growth more challenging and increases risks for poorly targeted investment and degraded harbours.

 

Solution:

A contaminant assessment of the inner and outer Waitematā Harbour was carried out by DHI using a coupled Freshwater Management Tool-Coastal Hydrodynamic Model. This helps estimate the contribution of freshwater-derived contaminants to the coastal receiving environment at close to 100 sub-estuary/harbour domains. Furthermore, an online Coastal Receiving Environment Scenario Tool (CREST) system was developed to view the baseline model results and compare them against agreed thresholds for each contaminant.