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Aucklanders don’t need to be persuaded that “one in a hundred years” rain can arrive in the space of a few weeks. On January 27, 2023 the Auckland Anniversary weekend storm delivered an estimated 245mm in 24 hours and around 160mm in six hours, an intensity the New Zealand Infrastructure Commission described as unprecedented in Auckland’s history.
In the weeks that followed, Cyclone Gabrielle added further strain to already sodden catchments: over 200mm fell across the Auckland region, with Waitākere recording 248mm, alongside damaging wind gusts.
Those events highlighted a underlying issue for an expanding city built around ridgelines, valleys, and coasts – flood resilience can’t rely on bigger pipes alone. It needs a mix of smarter planning rules, better site design, and property-level retrofits, because, many people won’t (and often can’t) simply relocate.
Plan Change 120: tighter rules where hazards are known
Auckland Council’s Proposed Plan Change 120 strengthens planning controls for development in places exposed to flooding and other hazards while still enabling housing growth in well-connected areas. Importantly, the natural hazard rules took immediate legal effect from November 3, 2025 even as the wider plan change continues through submissions and hearings.
For homeowners, the headline isn’t “you must move.” Council’s own Q&A states Plan Change 120 does not require anyone to leave their home, but it does tighten expectations for future builds and redevelopment, especially in higher-risk areas, so buildings are designed to be more resilient and don’t worsen risk for neighbours. In floodplains, for example, the council guidelines are that development may proceed where risk can be kept “tolerable,” including measures like safe evacuation routes and floor levels above flood levels.
Regulation matters, but it’s only half the story. Auckland already has thousands of existing homes and small businesses in harm’s way, and their resilience will be determined by what happens at the front door, the garage, and the driveway.
Think like a “sponge city” – that is, keep water out, and give it somewhere safe to go.
Globally, the “sponge city” idea describes stormwater systems that mimic the natural water cycle by infiltrating, retaining, storing, purifying, reusing and safely discharging rainwater to reduce flood peaks.
In the New Zealand context, the same approach is more commonly expressed as water sensitive design, water sensitive urban design low impact design, green infrastructure, and nature‑based solutions. These principles involve working with natural processes, avoiding further stream loss, protecting wetlands, and improving flood resilience.
Practical design moves
First, making space for water. One example is Greenslade Reserve in Northcote, where a playing field was designed to temporarily flood and then drain; during the Anniversary floods it reportedly held about 12 million litres over 15 hours, slowing flows that would otherwise have pushed through the town centre and homes.
Second, break up hard surfaces so rain can soak in or be slowed down before it reaches the street. That’s where permeable surfaces, rain gardens, swales, and tree pits come in, especially in suburbs dominated by roofs, driveways and parking.
Flood mitigation: barriers plus permeability
In a recent Hibiscus and Bays Local Board meeting, Auckland water solution’s company Watersmart presented a suite of measures that focus on making properties and communities more resilient, especially when warnings arrive with little time to spare.
One rapidly growing category is temporary or demountable flood barriers. WaterSmart’s “FloodFree” range describes demountable systems made of barrier segments with embedded seals, designed to be deployed manually by one or two people, and scalable in length. Their advantage over sandbags is reuse and speed. Modular barriers are designed to be stored and rolled out when a weather warning is issued, while sandbags are labour-intensive, and cannot be reused.
For fast-deployment at common entry points like garages, WaterSmart’s “Floody” is a portable, modular barrier that uses the weight of water to anchor itself, on flat surfaces such as asphalt or concrete.
Barriers work best when paired with measures that reduce water arriving at the wall in the first place, and permeable paving is one option. Watersmart’s “Porous Lane” product uses up to 60 per cent recycled tyre material, with stormwater and water-quality benefits (such as reducing suspended solids and certain pollutants), and a reported 20 to25 year design life. According to University of Melbourne testing, Porous Lane is eight to 10 times more permeable than an industry benchmark, In an Auckland CBD tree-pit case study on Mayoral Drive, Watersmart also reported reduced surface temperatures, which helps reduce heat-island effects and improved root-zone conditions. However, the upfront cost for installation are typically much higher than for asphalt or concrete.
Although planning rules can steer new developments away from the worst risk, the resilience for the city we already have will be built or rebuilt, through sponge-city thinking, targeted barriers, and the everyday decisions that determine whether water runs off hard surfaces into living rooms, or is slowed, stored, and safely drained away as part of the urban environment.
