Early Saturday brought a foretaste as the Missouri, whose level has risen nearly two feet in 24 hours, smashed through another levee, flooding some 3,000 acres of farmland near the suburban community of Chesterfield, about 15 miles west of the city. Hundreds of people were forced to abandon their homes.
Another 1,000 have been ordered from their homes in south St Louis, where the St Peres river, a normally dry drain-off channel now 50 feet deep in places, meets the Mississippi. The risk lies in 50 tanks of propane gas half torn from moorings by the raging waters. Overnight thunderstorms were pre venting divers yesterday from securing the tanks, heightening fears of a huge explosion.
If forecasters' current predictions are correct, however, the moment of truth will come today, when the Missouri crests at a record 39 feet at the largely submerged St Charles peninsula, just before it joins the Mississippi a few miles north of St Louis. At almost the same moment the Mississippi's own crest, driven by a month of torrential rains across its northern basin, is due.
The two-pronged onslaught will create an unprecedented crest of 49.3 feet on the Mississippi as it surges past central St Louis, more than two feet above the previous record of a fortnight ago.
With every passing day, even the dollars 4.1bn ( pounds 2.7bn) of emergency relief approved by Congress looks more inadequate. Estimates of total damage, including lost crops, wrecked factories and flooded homes, now range up to dollars 12bn. Across eight states, around 50,000 people have been evacuated; directly and indirectly, at least 43 people have been killed.