Old man river just keeps on rising and rising: Patrick Cockburn in West Alton, near St Louis, sees the Mississippi take its toll

ON THE earth embankment protecting the town of West Alton, just north of St Louis, the muddy brown water of the Mississippi was beginning to trickle through a line of sandbags. Men from the local air force base stopped trying to build the embankment any higher when they realised that the river was rising faster than they could build.

They expected the Mississippi to break through the levee, rising 15 feet (4.5m) above the fields, at any moment. Within a couple of hours the white clapboard houses of West Alton, already evacuated by most of its 500 people, would be half under water. 'We know it is going to happen, but I still hate waiting for it,' said Michael Yarbrough, the local sheriff.

Nerves are on edge. A local man, Alan, said that earlier in the day he and other men had waved their guns at a helicopter hired by a television company which landed on the embankment to let a cameraman film the flood waters. 'You could see the levee quiver where the helicopter set down,' he said. 'It would not take much more weight for it to go. We made the cameraman get back in the helicopter and take off again.'

Heavy rain over the last week has made the flood the worst in the Mississippi valley for over 30 years. In West Alton, the Roman Catholic Church of the Immaculate Conception still has a mark halfway up its walls showing the high point of the record flood of 1973. The few families still in the town say that if the waters do not get much higher than they did then, they will be safe in the top storeys of their houses.

That may be over-optimistic. The floods this year have kept getting worse just when they were expected to recede. In April heavy rain in the upper Mississippi - the river drains one-third of the US - saturated the soil in the region. When thunderstorms broke in early June, water drained off rapidly into the rivers. This week further storms deposited 6in (15cm) of rain in a day in some parts of Missouri, with the result that by next Tuesday the Mississippi will be 16 feet above normal flood level at St Louis.

In 1927 a flood like this killed 214 people in the lower Mississippi. Over the next half-century the US Army Corps of Engineers built 300 dams and reservoirs to make sure it did not happen again and, on the whole, they have succeeded in protecting the main towns.

Although sodden with rainwater, most levees are still holding, though the fields behind them are often unplanted because of the downpour.

It may get worse yet. In Grafton, a town of 1,000 upriver from West Alton, where the Mississippi and Illinois rivers meet, the only way to get down the main street is by boat. Vince Arnold, the retired owner of a bait and tackle shop, said: 'People don't realise that so long as the water is muddy it means that there is floodwater coming down from the north and nothing will get better.' He earns money by taking men from the local electricity company around the flooded houses in his boat, to cut off the electricity supply ahead of the rising water.

Navigating down the main street of Grafton, now under 6 feet of water, Mr Arnold said with some proprietorial pride: 'If it doesn't stop rising this is going to be the greatest flood in history.' The main danger, apart from the swirling floodwaters, is the live electric cables which are now only 4 or 5 feet above the water. Nobody in Grafton has died yet in the flood, but the town, which depends on visitors from St Louis, is cut off apart from one back road, and all its businesses are closed.

In Grafton city hall, which is still above water, Wilma Dillon, owner of the Two River Drive-In, is trying to arrange a boat to take her to see her restaurant. But boatmen say she is better off not going: it has almost disappeared beneath the Mississippi.