SAE Ltd ? Technical Writing
Technical writing on stormwater, flood assessment, and subdivision engineering in New Zealand. Written by Andre Magdich CPEng.
We have processed the latest 2024 LINZ LiDAR at 1m resolution across Auckland to produce 1.17 million overland flow paths. Free interactive map now live.
Read post →Impervious surface area is the primary input to every stormwater neutrality calculation. This guide covers what counts, how to measure it, how it drives runoff, and what NZ councils expect.
Read post →Every detention system will overflow - that is a design condition, not a failure. This post covers bypass capacity, overflow path sizing, freeboard requirements, and what NZ councils expect in the engineering report.
Read post →Stormwater treatment controls water quality, not flow rate. This guide covers swales, proprietary filters, and gross pollutant traps - what each does, how they are sized, and what NZ councils require.
Read post →SUDS works well on pumice soils and in Auckland SMAF areas, but fails on pallic soils, heavy clays, and steep sites. The decision should be driven by soil testing and council requirements, not sustainability aspirations alone.
Read post →Auckland, Wellington, and Hamilton all require stormwater neutrality, but the detail differs. This multi-council comparison covers typical consent conditions for detention, flood hazard, ESC, and three waters.
Read post →ROW drainage is almost always private infrastructure. This post covers ownership, maintenance responsibilities, design standards, easement documentation, and what NZ councils require at consent stage.
Read post →Retaining walls and stormwater fail together when designed separately. This post covers drainage behind walls, subsoil drains, erosion control, and NZ council building consent requirements.
Read post →Developer liability for flood risk in NZ subdivisions. LIM reports, floor levels, flood hazard overlays, insurance implications, and what proper disclosure looks like.
Read post →In February 2023, Cyclone Gabrielle delivered flood peaks consistent with the design scenarios used in the Tukituki River flood assessment. The assessed lots remained dry while surrounding properties flooded. Here is what the modelling predicted and what actually happened.
Read post →If your resource consent mentions stormwater neutrality and you're not sure what it means, this post explains the rule, the design approach, and why getting it wrong costs more than getting it right.
Read post →Auckland Council resource consent conditions are increasingly requiring 2D HEC-RAS flood studies ? not 1D. This post explains the difference, when each method applies, and what a 2D model actually produces.
Read post →Napier City Council formalised its stormwater neutrality standard SW-S1 in 2025. Here is how the first compliant subdivision at Barker Road established the methodology for every Napier development.
Read post →A 13mm orifice plate made a six-unit Napier subdivision stormwater-compliant. This post covers the hydraulic principles, design inputs, and sizing process for flow control devices on real NZ projects.
Read post →A 290-metre swale in Bulls or four underground tanks in Napier? The right stormwater detention solution depends on site constraints, soil type, and council standards.
Read post →Rangitikei stormwater rules differ from Auckland and Napier. Pallic soils rule out soakage, and Horizons RC requires careful interpretation of TP108 for Whanganui-region catchments.
Read post →Detention volumes come from the difference between pre- and post-development hydrographs. This step-by-step guide covers rainfall inputs, runoff methods, and which storm event controls the design.
Read post →A flood hazard assessment covers hydrological analysis, hydraulic modelling, climate change uplift, and site-specific flood depths. Here is what goes into one and what the outputs mean.
Read post →Three SCS variants produced Q100 estimates of 894, 1,129, and 1,186 m3/s on the Tukituki River. Understanding why they differ is what separates defensible methodology from guesswork.
Read post →How much climate change uplift to apply, and which RCP scenario, depends on your council, catchment, and design life. This post explains how HIRDS data flows through to flood design.
Read post →The Tukituki River flood study used 120 million LiDAR points. LiDAR processing for consent-grade terrain models requires filtering, datum correction, and validation against survey benchmarks.
Read post →Section 224(c) of the RMA is the final engineering gate before new titles issue. This post covers the documentation bundle, common delays, and how to plan your settlement timeline.
Read post →From feasibility through S224c, the engineering workload is front-loaded. This post maps every stage with realistic timeframes, deliverables, and fee distribution.
Read post →The fastest way to delay a resource consent application is to engage your engineer without the right information. Here is the seven-item checklist for the initial brief.
Read post →A 90-lot subdivision is rarely built in one go. Staging the consent correctly at resource consent stage allows S224c sign-off on completed stages without waiting for the full development.
Read post →A 0.543 m datum offset at Hereford Heights Marton propagates through every elevation-dependent calculation. This post explains the NZ vertical datum transition and how to apply the correct offset.
Read post →Potable water, wastewater, and stormwater each involve different council standards, design software, and approval pathways. Here is what the engineering deliverables look like at each stage.
Read post →TP108 is Auckland Council's primary stormwater reference, but applying it to a specific site requires judgement on design storms, pre-development cover, and attenuation sizing.
Read post →Auckland Council's flood viewer uses regional-scale modelling. A site-specific 2D HEC-RAS model at 1m resolution often reveals flood extents materially different from the regional mapping.
Read post →Whether your Auckland site has an OLFP1 or OLFP2 fundamentally changes the engineering response. Flow path categories affect lot layout, setbacks, fencing, and development viability.
Read post →Marton subdivision sits at the intersection of two regulatory frameworks. Getting both Rangitikei DC and Horizons RC consents to proceed in parallel requires an engineer who knows both.
Read post →Two Horizons-managed watercourses dominate Marton's drainage landscape. Understanding the discharge points and capacity constraints of each is non-negotiable for subdivision feasibility.
Read post →Pallic soils drain at millimetres per day, not metres per day. In the Rangitikei, your stormwater solution will involve detention and surface discharge, not infiltration.
Read post →A 1:500-year flood has a 0.2% annual probability and roughly 10% chance of occurring over a 50-year design life. Understanding return periods is fundamental to interpreting flood hazard maps.
Read post →The brief you provide determines the scope, fee, and programme. This checklist covers what to prepare, what to ask, and what deliverables to expect at each milestone.
Read post →Realistic programme ranges based on actual project timelines in Hawke's Bay, Rangitikei, and Auckland. Council processing times, engineering queries, and S224c completion.
Read post →Council flood maps are regional-scale models that sometimes classify safe land as flood-prone. Challenging the designation requires a peer-reviewed hydraulic model and a clear technical case.
Read post →Measured infiltration rates of 800 to 1,720 mm/hr in Bay of Plenty pumice soils. The design adopted a conservative 400 mm/hr. Understanding safety factors for high-permeability soils is critical.
Read post →At Kensington Road Marton, historical aerial photography from 1942, 1949, and 1982 demonstrated 80+ years of modified agricultural use, preserving the 41-lot subdivision yield.
Read post →EV charging conduit costs $400 to $800 per lot at subdivision stage. Retrofitting costs $3,000 to $6,000. This post covers power supply capacity, conduit specs, NZ Building Code, and council expectations.
Read post →Industrial and residential subdivisions share the same statutory framework but differ in stormwater treatment, NES-CS contamination requirements, pavement design, and fire-fighting water supply.
Read post →Every subdivision road is a stormwater catchment. NZS 4404 cross-sections, kerb and channel capacity, sump spacing, and pipe network integration - designed together, not sequentially.
Read post →Development contributions can exceed $500,000 on a 20-lot subdivision. Deferred payment through bonds, staged arrangements, and infrastructure credits under s200 LGA can ease the cash flow burden.
Read post →Have a project that needs a flood assessment or stormwater design? Contact us ? we respond within one business day.
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