AS IF the current spate of earthquakes and volcanic eruptions were not a sufficient reminder of nature's capriciousness and strength, two Louisiana State University professors have noted that the Mississippi River is still trying to do in New Orleans. Raphael G. Kazmann and David B. Johnson claim the river will change channels about 200 miles north of that city in "30 or 40 years at the outside." When it does so, they predict, the costs will be astronomical.

The Corps of Engineers, which is responsible for watching and controlling the Mississippi, is more sanguine. "We can't let it happen," a Corps spokesman recently told The New York Times. "We are charged by Congress not to let that happen." The official position of these official river-watchers is that it simply won't happen. To make sure, the corps will begin construction next summer on a $216 million auxiliary flood control system to back up the system that is already trying to keep the Mississippi where it is.

This is, so far as we know, the first major confrontation between modern engineering and a large river intent on going its own way. The Mississippi has changed course before -- several times in modern history -- and its effort to slop over into the Atchafalaya River basin was first spotted about 40 years ago. It would probably have made the switch by this time had not the Corps intervened so aggressively. As it is, every major flood holds a threat that the river will have a new channel when the water goes down.

What happens if the river, instead of the Corps, wins? Profs. Kazmann and Johnson suggest plenty might. In a report to the Louisiana Water Resources Research Institute, they predicted first-year costs at a "very conservative" $4 billion. The current channel might become a salt-water estuary requiring constant dredging to keep the docks in New Orleans open. Hundreds of factories along that channel might have to close down or modify their equipment to handle salt, instead of fresh, water. The pipelines that supply most of the East with natural gas might have to be rebuilt.The list goes on.

That's why nobody takes Old Man River lightly. The professors worry about it. The Corps fights it. Others wonder if the river ought to be allowed to make a tightly controlled shift.

Who will win as this slow-motion confrontation between humankind and nature goes on? No one really knows. But after watching Mt. St. Helens and listening to the guesses about its performance, if we had to bet, we would be on the river.