225 households that are permanent residences in a series of fishing camps. Mississippi state Rep. John Mayo, D-Clarksdale, pointed to a house flipped on its side as he surveyed the damage. "I don't know what these people are going to do. This is where they live," he said. Water from the river is expected to remain high into the summer, and flooding already has left in its wake flooded homes, weakened levees, thousands of evacuees and devastated farmland. The Atchafalaya River in southern Louisiana, overflowing with Mississippi water diverted through the Morganza spillway, was expected to crest Monday at Morgan City. It will be the final place along the Mississippi River system to get the highest water. Although the water has started dropping in northern Mississippi and Memphis, Tenn., an environmental crisis could be on the horizon in southern Louisiana. The fresh water rolling into the Gulf of Mexico could pose a serious setback for the badly damaged oyster industry, struggling to recover from last year's BP oil spill. Too much fresh water can kill oysters. "The worst is not over yet," said John Tesvich, the chairman of the Louisiana Oyster Task Force, an industry group. "We're starting to see freshwater in various areas. The next couple of weeks will be critical." The floodwaters have been the highest on record at more than half of the gauges along the fortress-like levee system built up between Missouri and Louisiana. Sandbags and emergency barriers have been placed around towns, at gaps in the levee system, and around businesses, power facilities and other critical infrastructure. So far, the Army Corps of Engineers is confident its flood system will hold up. And it's performed well so far, though crews up and down the river have had to chase sand boils -- where water undercuts the levee and land on the other side seems to boil. There will be a lot to watch over the coming weeks. Engineers say levees are weakened when floodwaters recede and erode the earthen ramparts. Also, there is the possibility for water levels to rise again as more storms dump water into the Mississippi River valley. At the southern end of the Atchafalaya River, there was a guarded sense of relief last week as the corps began closing bays at the Morganza spillway, source of the water threatening Morgan City, an oil and seafood town of about 10,000 people. The Atch