Residents of several neighborhoods in the New Orleans area that were hardest hit by flooding after Hurricane Katrina can sue the Army Corps of Engineers over their claims that a government-built navigation channel was largely to blame, a federal judge ruled yesterday.

Successful lawsuits against the corps could result in billions of dollars in damage payments.

Since the flood, those who lived in the devastated neighborhoods near the east side of New Orleans -- including the Lower Ninth Ward, New Orleans East and St. Bernard Parish -- have contended that the Mississippi River Gulf Outlet caused much of their damage by intensifying the surge from the storm. The damage, they say, was foreseeable.

After residents filed lawsuits, the government tried to get them dismissed. The corps argued that it was protected from lawsuits by the Flood Control Act of 1928, which grants it immunity from liability for flood damage caused by flood-control projects, like levees.

But yesterday, Judge Stanwood R. Duval Jr. of the Federal District Court for the Eastern District of Louisiana, cited previous cases saying that the channel was not a flood-control project. Instead, Judge Duval said, the cases say the channel -- known locally as Mr. Go -- was built as an aid to navigation, so the protection from liability might not apply. And so, he said, the questions deserved to be decided at trial.