Autumn leaves are the stuff of poetry. I’m especially fond of the French chanson standard with lyrics by Jacques Prevert, especially when sung by Yves Montand, who imbues the metaphor for a waning love affair with impeccable Gallic charm (I can almost smell the Gauloises).

But it would seem autumn leaves are rather less romantic in Cornwall. Anyone who drives through Truro will have encountered considerable inconvenience last week, when biblical downpours caused the city centre to flood. Especially afflicted was the area around Trafalgar roundabout, a nexus of the A39 ring-road which carries an estimated 30,000 to 40,000 vehicles daily.

Cars backed up towards Arch Hill, while some unlucky drivers had to abandon stranded vehicles in standing water, including one on St Austell Street outside Halfords. Police closed roads and implemented diversions; Cornwall Council later confirmed the floods had been caused by heavy rain close to high tide, with leaves and debris carried to the lowest points of the road to block drains.

This is a problem which has affected Truro’s streets in the past. Long-term residents took to Facebook with black-and-white images of waterlogged Kenwyn Street in the 1980s, and I myself recall having to pack a snorkel to navigate a particular underpass during wet conditions (I might be exaggerating). There are apparently plans for water storage tanks to alleviate drainage issues in the area.

It all reminded me of a keyboard warrior I saw on Facebook a year ago, moaning that the council was wasting precious time and money by clearing autumn leaves. “Don’t they know more are going to fall? That’s how deciduous trees work,” they snarked.

“You should try living on my hill,” I replied. When the monsoon hits, it turns into Niagara Falls, bouncing off drains which are clogged with leaf litter and parked on by school-run parents to boot (but that’s a whole other column).

Said council-botherer would have been happy to hear the National Trust’s woodland experts predicting a drawn-out display of autumnal colour, with trees considerately clinging onto their leaves thanks to a wet spring followed by a cool summer.

"It certainly feels like we are in for a wet, cold autumn, so it's more important than ever to go out and enjoy the last sunny days as the first signs of the changing emerge,” said John Lanyon, head gardener at Trerice, Trelissick and Glendurgan. “Soon we’ll be able to enjoy the stunning russet brown of our oaks, which are likely to hang on throughout the season.”

Forestry England, whose sites include Idless near Truro and Cardinham near Bodmin, agreed that abundant rainfall had helped forest trees grow well and produce lots of leaves full of sugars. They also took me back to the classroom with an explanation of why leaves change colour.

Remember photosynthesis? For the benefit of those who, like me, have forgotten most of the content of their science classes, here’s a reminder.

In order to grow, trees take water and nutrients from the soil, and use their leaves to capture sunlight, which green chemical chlorophyll transforms into sugary food. When the days get shorter and temperatures drop, the chlorophyll is broken down and stored in the tree roots over winter. As the green colour disappears, other pigments are revealed: carotenoids and xanthophylls, which can turn different shades of yellow, orange and red.

The bad news, according to the National Trust, is that while tree crowns remain at ‘full sail’, high winds and storms could cut the spectacle short before it reaches its colourful peak. It would have been alarmed by BBC warnings last week of hurricane-strength winds, not only in Cornwall but all over the UK. A glitch in the weather app caused predictions of wind speeds reaching 16,000mph — biblical indeed.

Looking out the window now, it’s lovely and sunny, and the rabbits are in their pen on the patio. It’s a good job they weren’t out there a few days ago; they would have been battered by the elements, namely rainwater bouncing out of our inadequate guttering in a way I have never seen before.

There was also a terrible smell. I asked Daughter discreetly if she or her visiting friend had, ahem, broken wind. “NO!” she insisted. I took a walk around the house; the stench was emanating from the back garden, where the sewers were clearly struggling with their load.

It was all very worrying, and it would seem that disaster awaits around every fall-tinged corner. Rural insurance experts Lycetts have warned of public safety issues around scarecrow festivals, bonfires and other outdoor gatherings, urging landowners and event organisers to ensure adequate permissions, insurance and safety measures are in place, and that bonfires are placed well away from dry crops and hay stores to prevent catastrophe.

But with this much rain, that might not be a concern.