The U.S. government will help the flooded city of Minot "for the duration," the Cabinet secretary responsible for federal disaster assistance said Wednesday, but also cautioned that North Dakota residents should better prepare for future disasters.

Homeland Security Secretary Janet Napolitano said the federal government "does not have deep pockets, nor is it a panacea," after taking a helicopter tour over the city where 4,100 homes have been damaged by Souris River floodwaters and more than 11,000 people have had to temporarily leave.

North Dakota also has seen record flooding along the Missouri River this summer, and eastern North Dakota went through its third consecutive battle against a flooding Red River last spring. Napolitano urged state residents in flood-prone areas to get flood insurance if they do not already have it.

Only 375 homes in the flooded areas of Minot had such insurance, according to the Federal Emergency Management Agency. The agency is making federal aid available to owners of private homes and businesses in the city and surrounding area. But Napolitano told residents that they should not expect the federal government to make them whole, because assistance is capped under federal law.

"We will provide what we can provide," she said at a podium placed against a backdrop of floodwaters in Minot. "Individuals may not be able to have what they had before."

Napolitano said about 7,900 North Dakota residents already had applied for federal assistance to help with flooding costs, and the U.S. government has doled out $13.3 million so far.

"We are prepared to do more as requests come in," she said.

Maj. Gen. David Sprynczynatyk, commander of the North Dakota National Guard, called Napolitano's visit "critical."

"Not just to hear about the costs but to also see the emotion and devastation," he said.

Sprynczynatyk said flood-related costs in North Dakota this year are expected to top $1 billion and that he thinks the state has met the threshold at which the federal government will cover 90 percent of the bill for public infrastructure repairs rather than the usual 75 percent.

He said the costs include about $410 million in flood-fighting and damage to public infrastructure, along with more than $600 million in damage to homes throughout North Dakota. The bulk of the damage is in Minot and surrounding Ward County, Sprynczynatyk said.

Gov. Jack Dalrymple told The Associated Press that the estimate of flood-related costs at more than $1 billion is "probably conservative."

He said Napolitano's visit was "pretty darn important for her to see the flooding firsthand, and I think she thought it looked very severe."

Dalrymple and Napolitano also took a helicopter tour Wednesday over the Devils Lake Basin in northeastern North Dakota, where the governor said hundreds of structures are flooded and some 30,000 acres of farmland has been lost to the rising lake since spring.