:Photo: RNZ

By Timothy Welch – The Conversation

We’ve built our cities to be vulnerable to – and exacerbate – major weather events such as the one we saw in Auckland on Friday. While almost no city in the world could fully escape the effects of four months’ worth of rain in 24 hours, there are many things that could have been done to avoid some of the worst impacts.

Buildings, streets and car parks are all impermeable surfaces. When it rains, the water rushes off these surfaces and into gutters. From the gutters, the water drains into a stormwater catch basin, through the stormwater network, and into streams and the sea.