New Orleans ? The engineers who designed the floodwalls that collapsed during Hurricane Katrina did not fully consider the porousness of the Louisiana soil or make other calculations that would have pointed to the need for stronger levees with deeper pilings and wider bases, researchers say.

At least one key scenario was ignored in the design, say the researchers, who are scheduled to report their findings at a congressional hearing today: the possibility that canal water might seep into the dirt on the dry side of the levees, thereby weakening the embankment holding up the floodwalls.

“I’d call it a design omission,” said Robert Bea, a University of California at Berkeley civil engineering professor who took part in the study for the National Science Foundation.