NY Times (reg. req'd):
Even as many found cheer that floodwaters along the Mississippi River here would fall well short of what had been predicted, residents and the authorities in this town discovered a stark reminder of what might lie ahead: a sand boil on the aged levee that protects the town, a telltale sign that the swollen river had begun eroding the structure from beneath.[..]
As the river at nearby St. Louis leveled out at around 12 feet below the record set during the 1993 flood and about two feet below what had been predicted for the weekend, investigators had identified and contained several more boils on the levee, and the marshland that sits just behind it had crept to within 100 yards of the village hall.
Last year, the Federal Emergency Management Agency, after consulting with the Army Corps of Engineers, found that the five-levee system that protects the metropolitan area of East St. Louis, Ill., did not meet its standards for flood protection.[..]
(A)s cities, towns and farms north of here have yielded in the past few weeks to the Mississippi's tremendous flooding, scientists have again emphasized a sharp increase in flooding in recent history. They say established communities like East St. Louis and neighboring Cahokia would be well advised to repair their levee systems.
"We have had two almost 100-year floods and two almost 500-year floods in a 35-year period," said Nicholas Pinter, a professor who specializes in flood hydrology at Southern Illinois University, Carbondale. "Flood levels all along this stretch of the Mississippi have climbed upward, not just by inches but by 8, 10, 12 feet - up to 18 feet over historical 100-year flood conditions. So the simple answer is that floods are higher and more frequent.
"But the underlying theme to everything that's going on," Dr. Pinter added, "is that the current estimates for flood frequency and intensity appear to be grossly underestimated."
Dr. Pinter maintains that while climate change and levee construction have contributed to increased flooding in the St. Louis area, the real culprits are river modifications made to ease navigation, which put further stress on the levee systems.