Rainfall Intensity

Rainfall intensity can be taken off the maps for 50-year average return intervals (ARI). When the co-ordinates of a site are known, site-specific values can be obtained using NIWA’s HIRDS tool at

As NZBC E1 requires that rainwater from events having 2% likelihood of occurring annually shall not enter buildings, the COP uses figures for 50-year Average Return Interval, rather than the 10% probability figures published in E1/AS1.


Revision Category: 
2 - Editing and rearrangement
Revision Detail: 

Rainfall intensity maps have been added to this clause. Links to rainfall maps have been included in the calculators.

Draft Clause: