Mother Nature has a habit of reminding us every now and then of her power.

People were stranded at home yesterday after fords rose and cut off driveways.

Floodwaters and slips blocked roads and highways. Schools and businesses closed.
And wastewater systems became overloaded.

Napier's wastewater system occasionally overloads, in heavy rain.

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Read more: Heavy rain, flooding and thunderstorms hit Hawke's Bay

This week's rainfall was enough for the system to overload and for the council to make a plea for city residents to only release wastewater when they have to.

That means only bath or flush the toilet when you have to, and keep your showers short until Friday.

Hawke's Bay Civil Defence's group controller, Ian Macdonald, says the bad weather was a "two-to-three-year event".

Remember the 100-year-old floods a decade or so ago? We had two in close proximity.
So for the Napier system to creak after this week's rainfall, will concern the town's council and wastewater experts.

What happens in Napier isn't unusual.

Around New Zealand, town stormwater and sewerage systems sometimes mix together in heavy rainfall, and you get a diluted, disgusting sewage soup going into waterways and harbours via stormwater systems.

That's because our stormwater and sewerage systems are old, and expensive to fix. In some towns around our clean green country, stormwater goes straight into sewerage systems. Band aids don't work - eventually they bust. And at some point councils have to find the money to sort out holding tanks, or pipes, or treatment systems.

I lived in Whangarei when that town's sewerage and water treatment system was so broken, the district council had consent from the regional council to dump over 20,000cu m of sewage into the local harbour.

To its credit, Whangarei fixed the problem in response to an uprising from the locals, one of whom was so incensed he dumped a bucket of raw sewage in the council foyer.

Napier has a monitoring system that allows it to make a plea like it did yesterday - help us out before we have a spill.

And there are plans already in train to upgrade the stormwater and sewerage systems, so that Ahuriri is a pristine treasure.

Let's just hope there are no "once in a 100 years" floods.