02/09/2026
Auckland's stormwater design standard hasn't changed since 1999. TP108 (2026) is out for feedback now - and the movement is at the rare end. In the document's own worked example, the 100-year storm goes from 200mm to 250mm in 24 hours. That's the number used for flood levels and minimum floor levels.
Feedback closes 7 September 2026. Full breakdown and the proposed depth table: https://www.crestonproperty.co.nz/resources/tp108-2026-auckland-stormwater-update