Other, highly poisonous, cottonmouths had probably tried to escape the rapidly rising river by taking refuge amid his tables and chairs, so he abandoned a plan to save his belongings by tying them to the roof of his house.
Even the roof may not be safe for long. Mr Schriewer's house stands on stilts on the Missouri bank of the Mississippi opposite Alton, just above St Louis, where the river is about a mile wide. But when the floodwaters broke through the levee, or earth bank, behind his house last week, the width of the Mississippi suddenly more than doubled. Now the only way he can reach his house is to travel in a flat-bottomed boat two miles through fields and woods flooded to a depth of 15ft. The river is already 12ft above flood level at Alton and is expected to rise another 5ft by next week.
Flooding along the Mississippi and its tributaries has caused 16 deaths in four states since late last month. Officials estimate crop and property damage in the billions of dollars. Unrelenting rain still drenched the Midwest yesterday and the levees continued to give way, flooding farmland and small towns.
In Missouri, 7,000 people living to the north of the city of St Louis were told to head for higher ground. In the city itself, the downtown area was protected by floodgates that can hold back water up to 52ft above flood level. But water spilled on to low-lying areas outside the city centre. Heavy rain, high water and washouts stopped all the railways running through Iowa. Thousands have been forced from their homes in Minnesota, Wisconsin, South Dakota, Iowa, Nebraska and Missouri. Weather forecasts threaten thunderstorms persisting into next week.
The Mississippi is famous for bursting its banks. A 1927 flood, which did not reach 1993 levels, killed 217 people. The 300 dams and reservoirs built by the Army Corps of Engineers since the 1920s were intended to make the river more tractable. But nobody expected the flood so late in the year. The river was already at flood stage in June when a series of thunderstorms started. In Iowa last week, 8in of rain fell in one night on ground that cannot hold any more water.
One of the worst affected areas is the flood plain just north of St Louis where the Missouri and Mississippi meet. As the water rose in both rivers, the 20-mile long tongue of land between them began to disappear under water. At Portage Des Sioux, built by French traders in the 18th century, Randy Schmidt, an aircraft mechanic, was watching the water advance to within 50ft of his house. He did not expect the wall of sandbags he and other townspeople had built to do much to stop it. 'Every sandbag I've thrown down has been washed away,' he said. 'A wall of sandbags will buy you time, but if there is a weak point in the levee, the water will break through. There are no sandbags in the world that will help you then.' All other roads in the town ended in walls of sandbags, giving it a military appearance, as if it was expecting to be attacked.
Earlier in the week, the people in West Alton, 10 miles away across the flood plain, were philosophical about impending inundation, pointing to water marks left by the last big flood in 1973.
Elmer and Elizabeth Schaub said they planned to stay in their house and keep in touch by boat. They expected their basement and ground floor to be flooded, so they had piled their belongings on another floor. But the resolution to stick it out seemed to evaporate when the floodwaters broke. Going past West Alton in a boat the day after it was flooded, there was no sign of the Schaubs. Much of the levee had disappeared, and the grass that grew on its top was waving like seaweed just below the surface of the water.
Some of the home-owners were carrying guns to deter looters. Endre Schwarts, with a pistol strapped to his belt, was watching his parents' house. Warren Ryan, a skilled boatman and former member of the Coastguard, was worried his efforts to rescue neighbours' belongings in his boat might be misinterpreted. 'Some of these are real country people and they will shoot,' he said.
The flood plain between the Mississippi and the Missouri is impossible to protect, and by Friday police were evacuating people from around St Charles, the old French capital. Some towns without earth levees, such as Davenport in Iowa - where Ronald Reagan once worked as a radio sports announcer - and Grafton in Illinois, are already largely under water. In other towns beside the river, people listen obsessively to the forecasts from the National Weather Service about how high the river will rise in their region.
It is the older wooden clapboard towns, built by the first settlers on the banks of the Mississippi, that are suffering the worst damage. In addition, the heavy rain across the Midwest is costing farmers more than dollars 2bn because they cannot harvest their corn and soybean crops. President Clinton is promising dollars 1.2bn in relief funds.
The floods have also halted the tugs and 200ft-long barges that ply the Mississippi. One thousand barges, with 1.5m tons of coal, oil, chemicals and grain, have been stranded on 500 miles of river north of St Louis. They are likely to stay there until at least August.