It never rains…
…but it pours, especially in Porirua today, causing sudden flooding and serious disruption.
I downloaded the hourly rainfall data from Greater Wellington’s site (a rather painful manual process, but a big improvement from not long ago, when you could only get the charts as static images) and put together a quick graph. Here are cumulative rainfall totals for today, for selected stations in the region arranged roughly from north to south.
Unfortunately there’s no station in Porirua itself, but the one just upstream in Tawa received the greatest total. 60mm in a day is not a huge total in itself, but most of it came in two or three hours before 9am, peaking at a torrential 20mm/hr. MetService’s radar caught the deluge at its height:
— MetService (@MetService) May 4, 2016
Taupo Stream (just north of Plimmerton) also caught a good 50mm, and I suspect that there were very localised falls in Porirua that were even higher. I saw a few complaints on social media along the lines of “Typical! A little bit of rain and the infrastructure can’t handle it”, but when you get half a month’s rainfall in a couple of hours, most drainage systems would struggle to cope…especially in floodplains and reclaimed mudflats.