After the debate that last week’s post provoked (and thanks to everyone who commented, online and offline), I thought I would write about something slightly less contentious this week – sheep, for example. But the first thing that came to mind was, um, flooding.

I’ve always remembered reading a leaflet from an environmental agency. It said that six inches of fast-running water is enough to knock a person off their feet, while two feet is enough to float a car. That sharpens my appreciation of the danger faced by people in some of the worst hit parts of England over the last few weeks. I picture the swollen River Severn within inches of the tops of the arches of Worcester Bridge and imagine the power in that torrent. It’s a salutary reminder to anyone who thinks that we have tamed the natural environment.

A few hundred yards from my house runs the River Tay. It’s the longest river in Scotland and by the time it reaches the sea it’s discharging more water than any other river in the UK. Fortunately we’re above the high-water level, which is just as well because it does flood. It used to be dredged naturally as people extracted gravel for commercial use, but these days environmental regulations, particularly to do with salmon, mean that much less dredging is allowed and when sections of bank collapse, as they do when the river is in spate, the silt and gravel simply falls to the riverbed, pushing up the water level still further.

In January 1993, shortly after I had returned to Scotland, there was a very heavy snowfall followed by a sudden thaw and a couple of days of torrential rain. The Tay’s catchment area is vast – 2,000 square miles – taking in the whole region directly south of the watershed that divides central Scotland from the Highlands. Every loch and burn in that tangle of mountains feeds eventually into the Tay. That January it roared down to engulf the low-lying areas of Perth, causing damage worth £10 million and driving 1,000 people out of their homes. It was shocking to see the now all-too-familiar images of rowing boats in housing estates.

The morning after the flooding had peaked, I was driving down the A9, the main road from Inverness, which follows the river directly for ten miles or so north of Dunkeld, where I now live. On the other side of the river, perhaps half a mile from the road, runs the railway line. At one point I glanced across and was astonished to see what looked like a length of rope dangling above an expanse of floodwater. In fact it was a 400-yard stretch of railway line where the embankment beneath had simply been scooped away by the water to leave the line, still attached at both ends, hanging in mid-air.

Later I heard someone from Scottish Hydro-Electric (now SSE) talking on the radio about the volume of water that had been flowing into Loch Faskally the previous day. Loch Faskally is the man-made reservoir contained by the dam on the river Tummel at Pitlochry, a dozen miles upstream of Dunkeld. The loch is two miles long and about half a mile wide.

The Hydro spokesman volunteered this extraordinary hypothesis: had the reservoir been completely empty at nine o’clock the previous evening, when the flooding was at its peak, it would have filled to the brim in 17 minutes. In other words, one could have stood on the bank and watched a two-mile-long loch filling up like a bath. Needless to say the floodgates on the dam were all open to the maximum and still the water was licking at its rim.

It’s easy to write this from the comfort of a warm, dry house that should be safe from all but the most apocalyptic levels of flooding. But to see your furniture and possessions floating round your living room in fresh river water, let alone foul groundwater, must be the most appalling thing imaginable. My heart goes out to the poor people in the undredged parts of the Somerset Levels and the un-sandbagged parts of the Thames Valley. For them this reminder of our powerlessness in the face of nature comes too close to home.