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Whangarei Catchment Upgrade and Options Model

Background and Objectives

Since 2009, Ewaters has been involved in the modeling of Whangarei's rivers. In 2022, we embarked on an ambitious upgrade of the existing Infoworks RS river models to Innovyze InfoWorks ICM (Integrated Catchment Management), incorporating the urban pipe network to better analyze and address flood risks in both riverine and urban areas.

The NRC initially engaged Ewaters to upgrade the Infoworks RS river models for the Whangarei catchment. This upgrade aimed to improve the understanding of catchment hydrology and hydraulics for accurate flood risk assessment. In May 2022, WDC requested the inclusion of the urban pipe network in the model, prompting NRC to extend our engagement to integrate this component during the model upgrade.

Comprehensive Model Upgrade

Technical enhancements in the model upgrade include mainly the following aspects.

·    Model Conversion: Ewaters team converted the Infoworks RS model to Innovyze InfoWorks ICM to handle the complexities of large pipe systems.

·   Expanded Coverage and Features: The upgraded model now covers the Hatea, Limeburners, Raumanga, and Wairohia River catchments. This 1D/2D coupled model includes essential features like the Waiarohia reservoir, various waterfalls, and newly built flood mitigation structures.

·   Enhanced Terrain Data: The 2020 LiDAR data acquisition enabled us to provide complete 2D coverage of urban areas, which were previously not covered.

·    Pipe Network Inclusion: By incorporating pipe sizes of 450 mm and greater, we ensured a comprehensive assessment of flood risks within the urban areas, addressing pipe capacity and localized flooding issues.

Benefits of Integrated Model

·   Enhanced Analysis and Mitigation: The upgraded model facilitates the analysis of dynamic interactions between the river and pipe systems, considering tidal influences and future climate change scenarios. This integrated approach enables more accurate flood risk mapping, model calibration, and testing of flood mitigation options for both NRC and WDC.

Supporting the Blue Green Strategy: The recently adopted Blue Green strategy by WDC emphasizes efficient urban water management. Our upgraded model supports this ethos by accurately describing local flooding and stormwater management. It provides a tool for testing traditional and water-sensitive solutions, promoting sustainable urban infrastructure development.

GIS Geometric Network: Total pipe + river network

Future-Ready FEWS System

By upgrading the existing model to Innovyze InfoWorks ICM and incorporating 2020 LiDAR data, Ewaters have achieved a highly accurate and comprehensive analysis of both riverine and urban flood risks of Whangarei Catchment. To further enhance flood risk management, Ewaters has explored the integration of the upgraded model with the FEWS system, enabling advanced monitoring and early warning capabilities.

FEWS (Flood Early Warning Systems) system is a customizable information management tool designed to meet diverse water resource needs. Originally developed for flood early warning, FEWS now integrates GIS mapping functionality with time series data, offering comprehensive analysis and display capabilities.

FEWS can process and display time series information, making it invaluable for planning, design, operations, and civil defense. It supports a wide range of data analysis, including river cross sections, pipe network capacities, and real-time storm events. This flexibility ensures that both NRC and WDC can utilize the model for efficient asset management and infrastructure decision-making.