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Ahead of the World Surf League (WSL) event in Raglan, a new operational platform has been launched: SeaScope Surf. The system provides a high-resolution digital twin of the Raglan coastal domain, designed specifically for surf forecasting, operational oceanography, and coastal decision support.
The platform integrates real-time observations, multi-source numerical modelling, and statistical wave diagnostics to deliver a unified representation of surf conditions across all major Raglan breaks, including Manu Bay, Whale Bay, Indicators, and Ngarunui Beach. As outlined in a previous post, we implemented a high-resolution hydrodynamic domain to drive dispersion modelling of the untreated wastewater continuing to be discharged from the long outfall at Moa Point, Wellington. This also provides useful insights into the circulation within Lyall Bay and implications for water quality. Lyall Bay can be thought of as two connected systems; the inner Bay, with a mostly clockwise flow regime, and the outer Bay which typically has a counter clockwise circulation pattern. See Figure 1 for the main flow patterns.  Figure 1. The red cross indicates the outfall location. During low wave conditions, the inner Lyall Bay water remains quite isolated from the outer Bay and the adjacent coastal circulation and its strong tidal flows. This amount of disconnection has two important effects from a water quality perspective. While untreated sewage from the offshore outfall has no direct path to the inner Bay, any sewage that does enter the inner Bay (for example due to previous weather conditions) is not readily flushed out. See Figure 2 for a typical low wave flow map.  Figure 2. During high waves and southerly wind conditions, a very different picture emerges - particularly during the outgoing tide stage. Here, sewage discharge from the outfall connects with a strong onshore directed flow along the west side of the outer Bay, directing sewage toward the inner Bay and the shoreline. During these southerly storms the inner Bay has a distinct clockwise circulation pattern, which means the sewage is distributed all along the beach and only slowly disperses out to the adjacent coast. See Figure 3.  Figure 3. During energetic waves events, onshore Stokes drift will further enhance the potential for pollutant connection with Lyall Bay and should be included in dispersion simulations (Figure 4). Our modelling has also shown it can lead to an underestimation of intrusion within the harbour if omitted.  Figure 4. Overall, this is not a straightforward process — the configuration of these circulation cells is strongly modulated by the interplay of tidal stage, wind, wave energy, and wave incidence. A high-resolution model is therefore valuable to reliably drive the dispersion modelling.
These insights can be applied operationally to help time outfall shutdowns or flow reductions during periods when connection with Lyall Bay is most likely. We hope these tools serve as a valuable resource for identifying and planning around expected pollution peaks while the issue remains unresolved.
Pollution in coastal waters is a growing concern, affecting marine ecosystems, fisheries, and local communities. To better understand the current conditions in Wellington Harbour, we have developed an interactive map showing the distribution and movement of pollutants in near-real-time.
The map is based on hydrodynamic simulations using our 3D SCHISM model, which accounts for tides, currents, and water mixing, combined with a Lagrangian model that tracks water masses over time.
Using the slider below, you can explore the spread of the wastewater plume at different times of the day. Click on the map to view a timeseries for a specific location. The values range from 0 to 1, where 1 represents the maximum concentration at the pipe, and 0.5 indicates the plume has been diluted by half. Using this tool, residents, researchers, and decision-makers can:
About the Data
Our model is updated daily using data from the Oceanum Datamesh platform. The map shows surface pollution concentrations. The app can access directly here www.seascope.io Over the past years, Calypso Science has been developing high-resolution hydrodynamic representations of New Zealand’s coastal and shelf waters. Early work focused on a national hindcast, which provided a 3D baroclinic reconstruction of currents, temperature, salinity, and tides across the country (National data cube). Building on that work, thanks to PredictWind, we have now deployed a fully operational, national-scale forecast using SCHISM, capable of delivering hourly 3D fields of velocity, temperature, and salinity across the entire New Zealand domain.  |
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