Summary
- Tauranga City Council (TCC) owns and operates the city’s public stormwater system, which includes 626 km of stormwater mains, five pump stations, and blue-green networks that help manage flooding.
- Other stormwater-related activities include flood modelling and hazard mapping, stormwater management planning, and consenting.
- TCC’s programme of work is a sustained response to stormwater management: “creating the resilience needed to reduce the impacts of flooding, and degradation of water quality and ecosystems caused by stormwater, in the face of challenges such as rapid urban growth and climate change.”*
- To help deliver this work, TCC’s Stormwater Panel provides innovative stormwater planning, design, and applied modelling.
- The panel’s six consultants cover four areas: Specialist Modelling Assistance, Stormwater Planning, Engineering Design, and Applied Modelling.
- Since 2018, Awa Environmental has been the sole Specialist Modelling Assistant on the panel.
- TCC has one of the most mature approaches to stormwater modelling in Aotearoa New Zealand due to its ongoing investment in data, methodology, and model updates.
- To date, Awa Environmental has delivered over 80 projects, including model builds, flood mapping, hydrology, stormwater capacity assessments, flood risk assessments, and guidelines development.
- We also provide peer review and ad hoc, expert advice on a wide range of stormwater and modelling topics to TCC, fellow panel members, third-party consultants, and others.
Challenges
- TCC is legally required to maintain a 10-year Long-term Plan (LTP) for works and expenditure, and a 30-year Stormwater Strategy.
- The current strategy (2024-2054) aspires to:
- Ensure Tauranga’s water cycle is sustainable
- Support safe, resilient communities with value for money solutions
- Manage stormwater in ways that are culturally appropriate and support Te Mana o te Wai (focused on restoring and preserving the balance between water, the wider environment, and the community).
- Delivering on these aspirations requires overcoming challenges that include:
- Reversing degradation of streams and other watercourses
- Supporting sustainable urban growth
- Improving resilience
- Working with Tangata Whenua and the wider community
- Responding to evolving regulations.
- Stormwater models are central to this work, underpinning:
- Flood risk assessment and hazard mapping
- City Plan stormwater provisions
- Impact assessments for urban growth and infrastructure projects
- Level of service assessments
- Progression of LTP projects to detailed design
- Low Impact Design (LID) / Water Sensitive Design (WSD) solutions
- Catchment base model builds, updates, calibration, and validation
- Strategic planning
- Stormwater upgrade planning and investigation.
- That means it is critical for TCC, the panel, and other stakeholders to have up-to-date, reliable, and fit-for-purpose hydrological and hydraulic models and modelled outcomes.
- For these models to remain useful, they must remain accurate and trusted, so they need regular maintenance and good management.
- They also need to be used efficiently and effectively, which means having documented, best-practice methods plus clear, readily available guidelines & support.
- Continuous innovation in methods, tools, techniques, and technology is required to ensure timely delivery of high quality, rich outputs.
Solutions
Flood Modelling Methods and Guidelines
- As Specialist Modelling Assistant, Awa Environmental steers the building, updating, and validating of TCC’s high resolution 1D-2D coupled stormwater models to reflect changes in data, advancements in technology, and emerging methodologies.
- The original models were built approximately 10 years ago, so in 2020 we conducted a comprehensive audit and are leading the work to update them and related data.
- We have generated consistent city-wide, model-ready information such as hydrological inputs, surface roughness, building footprints, rainfall, and tide boundaries, which enable greater consistency between models and easier updates.
- We also developed “cut down” models for faster optioneering and assessments.
- Beyond model builds and updates, Awa Environmental defines and sets standard methodologies and approaches, and reviews modelling software.
- For example, we produced new modelling guidelines for TCC and the Bay of Plenty Regional Council.
- We also conduct peer reviews to assure TCC that modelling work is fit-for-purpose.
- More broadly, we facilitate continuous knowledge sharing and upskilling across the panel.
Digital Solutions
- Another important aspect of Awa Environment’s panel role is model and data management.
- Our innovative Model Manager platform is a cloud-based system that streamlines modelling workflows and data management. providing:
- Secure and easy large file uploads
- Service desk technology to manage model metadata, model dissemination, and model data upload requests
- Web-based mapping to navigate through available model versions and associated data
- A knowledge base repository
- Activity tracking and reporting
- Quality assurance and data archiving tracking.
- This ensures a well-maintained database of base and project model versions, with corresponding metadata, is available for end users.
- It also supports continuous improvement of model management and maintenance.
Benefits
- As Specialist Modelling Assistant, Awa Environmental helps TCC deliver its stormwater programme effectively and efficiently, in line with the LTP and the Stormwater Strategy.
- The quality of our leadership, innovative thinking, technical expertise, responsiveness, collaboration, and project resourcing and delivery has been vital to continuous improvements in models, modelling processes, and panel operations.
- We have developed and/or refined best practices and specialist methodologies and tools to improve modelling service delivery, and enhanced the quality, usability, and traceability of TCC’s models.
- Our Model Manager platform has been pivotal, by:
- Improving efficiency of model management
- Reducing rework and data loss
- Accelerating access to insights and communication between model stakeholders
- Making it easier to update models
- Streamlining peer reviews
- Increasing institutional knowledge of things like model versions and model history metadata.
- Thanks to Awa Environmental, TCC’s models are more detailed, accurate, easier and quicker to use for a host of applications, including flood risk reduction, building community resilience, planning, and decision making.
- As models grow in complexity, size, and importance as a tool for communities to tackle major challenges such as climate change, improvements like these are crucial to ensuring their ongoing utility and value.
*30-Year Stormwater Strategy 2024 – 2054, Version 1, Tauranga City Council, May 2023
