Flood Risk Management Strategy – Inner City Council

A Melbourne Inner City Council requested a Flood Risk Management Strategy, which commenced in December 2024 and is being delivered in four phases by Rain Consulting. The Strategy looks to the year 2100 and creates a 70-year implementation roadmap of actions within a monitoring framework.

Phase 1: Rain Consulting prepared Phase 1 of the Flood Risk Management Strategy in December 2024. The first deliverable reviews how new climate-adjusted flood mapping for the year 2100 affects the municipality, validates the modelling with historical and community data, and frames a path toward a comprehensive mitigation plan. The work combines technical flood analysis, stakeholder engagement and policy integration to lay the foundation for long-term resilience.

Phase 2: Rain Consulting is preparing Phase 2 – Deliverable 2: A detailed action plan for the Flood Risk Management Strategy. The plan converts new climate-change flood mapping into a prioritised, 70-year program of mitigation actions. It weaves together engineering, planning and community engagement to guide the council toward safer, more resilient neighbourhoods.

Phase 3: Rain Consulting is delivering Phase 3 – Development of the Prioritisation Program for the Council’s Flood Risk Management Strategy. This stage transforms high-level flood-risk findings into an actionable, 70-year roadmap by ranking mitigation works, defining responsibilities and establishing a monitoring framework. The work builds on earlier strategy phases and aligns with Council policies, Melbourne Water inputs and national flood guidelines.

Phase 4: Rain Consulting is undertaking an independent peer review of Melbourne Water’s draft flood models covering several Council catchments. The review will assess the technical robustness, planning scheme readiness, and property scale accuracy, enabling the Council to confidently transition the program from its current “hold point” to completion.

Above & Beyond Strategies

Phase 1: The Council required an evidence-based understanding of future flood hazards under climate change, so it could prioritise investment, embed flood risk into planning controls, and communicate clearly with its community. Rain worked to validate recently produced city-wide models, reconcile them with on-the-ground and social media observations, and transform complex data into an actionable, council-wide risk-reduction roadmap.

Phase 2: Council needed a clear path from raw flood-hazard data (including projections to 2100) to shovel-ready projects and policy changes. This work required reconciling technical modelling, multiple internal strategies and external stakeholder input while ensuring alignment with national flood guidelines.

Phase 3: A clear and defensible approach will determine which flood-mitigation projects to fund first, sequence over time, and track success while accounting for climate change, community expectations, and budget constraints. Rain converted diverse technical data and stakeholder priorities into a single, transparent investment framework.

Phase 4: The Council must decide whether the draft models constitute the “best available information” and are therefore defendable for a planning scheme amendment, while avoiding unreasonable burdens on the community. The challenge is to confirm technical quality, spatial accuracy and compliance with Planning Practice Note 12 within tight timeframes.

Rain is delivering the following solutions.

Phase 1:

• Review Australian Rainfall & Runoff v4.2 hazard classifications and tailor them to local conditions – delivered a municipality-specific hazard matrix.
• Collate, quality-check, and map historic flood evidence (including community, First Nations, and social media sources) – set up workflows and guidance for ongoing data capture.
• Validate new 2100 climate-change flood models – reran events and produced side-by-side maps for transparency.
• Identify properties where floodwaters could enter buildings – generated parcel and building-level depth datasets for two design events.
• Audit internal policies, capital works programs and planning controls – completed gap-analysis memos and ran two targeted staff workshops.
• Benchmark best-practice flood management legislation and external council strategies – produced comparative tables and recommendations.
• Classify high, medium and low municipal flood-risk zones – created GIS layers to support service-level decisions.
• Estimate Average Annual Damages (tangible and intangible) – agreed criteria with Council and completed calculations.
• Draft a high-level Flood Risk Reduction Plan that links modelling, risk appetite and community education – issued for review with visual maps and tables.

Phase 2:

• Produce a detailed, cost-effective action plan covering WSUD, open-space actions, maintenance, education and planning controls.
• Prioritise capital drainage upgrades with GIS analysis and add up to ten additional high-risk locations for future works.
• Rank existing and proposed integrated water solutions (rain gardens, tree pits, GPTs, wetlands, permeable paving) for the most flood-risk reduction.
• Estimate roof-water harvesting and open-space detention potential to support reuse and attenuation targets.
• Incorporate policy changes and planning-scheme amendments using Tract’s specialist advice.
• Deliver a funding and investment framework that links hazard reduction and average annual damage (AAD) benefits to business-case decisions.
• Identify education actions, emergency management improvements, and advocacy opportunities with Melbourne Water and state agencies.
• Map and rank Council assets needing resilience upgrades, and propose maintenance enhancements such as sensor-enabled pits.

Phase 3:

• Analyse new flood-mapping data to 2100 and quantify Average Annual Damages reduction — Rain’s flood-modelling team will assess up to 20 capital works and 10 WSUD/IWM options across two AEP events.
• Create a practical, ranked program of works using a custom criterion and investment framework rooted in AAD, hazard reduction, longevity and multi-functionality.
• Integrate with existing Council strategies (WSUD, open space, and planning overlays) and align with Australian Rainfall and Runoff v4.2.
• Facilitate collaborative workshops to refine rankings and assign roles, ensuring cross-department accountability.
• Develop a tabulated implementation plan that details timeframes, budgets, and responsibilities for the next 5-10 years and beyond.
• Establish a reporting framework and KPIs that enable two-yearly reviews and embed community feedback loops.
• Provide robust project management and fortnightly progress reporting to keep the Council fully informed.

Phase 4:

• Determine if model outputs are suitable for a planning scheme amendment.
• Confirm the usefulness of outputs for day-to-day development advice (such as setbacks and finished floor levels).
• Assess whether the results can inform future projects and flood-risk strategies.
• Review reports against Melbourne Water Technical Specifications and PPN12 criteria.
• Audit flood-extent delineation and check levels against terrain using GIS diagnostics.
• Analyse hazard mapping to distinguish depth-driven versus velocity-driven risk areas.
• Provide confidence notes and tabulated defendability assessment for each study.
• Cross-check proposed overlay extents against the updated cadastre (Digital Cadastre Modernisation).
• Deliver a concise public-facing report that sets out methodology, recommendations and clear conclusions.
• Facilitate progress meetings to keep the project on track.

Phase 1: Rain produced validated flood-extent maps, a property-level impact database for 5 % AEP and 1 % AEP + CC events, a prioritisation framework tied to Council’s service levels, preliminary whole-of-city mitigation cost estimates, and a draft Flood Risk Reduction Plan that sets strategic actions, responsibilities and community-engagement measures. These outputs give Council a clear, defensible basis for programming works and updating planning overlays.

Phase 2: Rain will provide a draft and final Action Plan report containing spatially mapped priorities, project timelines, responsible teams and funding pathways. The work packages enable the Council to stage implementation, secure co-funding, and update priorities as climate data evolves.

Phase 3: Rain has prepared a ranked portfolio of flood-risk reduction projects, a costed implementation schedule, a roles-and-responsibilities matrix, and a KPI-driven reporting framework. These are all consolidated in the Draft Flood Risk Management Strategy Report. These outputs give the Council a clear, evidence-based pathway to reduce flood risk over the next seven decades.

Phase 4: Rain will supply a defendable matrix for all six models, with GIS diagnostics highlighting any critical issues, and a succinct peer-review report suitable for public exhibition. These deliverables will provide the Council with a clear yes/no position on using the models for overlays, development advice, and strategic planning.

A Flood Risk Reduction Roadmap to 2100.

Phase 1: Rain will refine the Flood Risk Reduction Plan based on stakeholder feedback and progress optional remodelling in light of the latest climate change scenarios. Deliverables 2 and 3 will detail the 70-year implementation program and business case development.

Phase 2: Council and key stakeholders will review the draft, followed by a workshop to refine actions and agree on delivery sequencing. Subsequent modelling of shortlisted mitigation options will confirm performance before detailed design.

Phase 3: Council will review and endorse the prioritisation program, then proceed to detailed design and funding of the highest-ranking works. Rain will support biennial progress reviews and update rankings as new modelling or community feedback emerges.

Phase 4: The work will run over a two-month program, with interim findings shared to support the Council’s dialogue with Melbourne Water. The team will schedule progress meetings and prepare the final report for Council endorsement.