NAGS HEAD, N.C. — Hurricane Dorian finally made landfall in the United States on Friday morning on North Carolina’s Outer Banks, where it knocked out power, flooded homes and businesses, and temporarily trapped residents of remote Ocracoke Island, where floodwaters reached up to seven feet.

The blow to the Outer Banks, a 120-mile strand of narrow barrier islands that is a veritable magnet for hurricanes, was a reminder of the menacing power the storm retained, even as it decreased in strength to a Category 1. Forecasters expect Dorian to move on Saturday over Nova Scotia, where the Canadian Hurricane Center has issued a hurricane warning for the eastern portion of the province.

The most frightening moments Friday morning occurred on Ocracoke Island, at the southern end of the Outer Banks. Donald Shumate, a spokesman for Hyde County, N.C., said the storm had brought a rapid rush of floodwater that had risen to seven feet, sending residents scurrying to their second floors and attics.

Susie Fitch-Slater, 60, the pastor of Ocracoke United Methodist Church, was shocked by its speed. One moment, she said, she was looking at small puddles in her backyard. A moment later, she said, the entire yard was flooded. “I am from the Outer Banks,” she said. “I was born here. And I have never seen anything like this before. I went into the attic, and I have never done that in my life. There was that moment when you wondered if it was ever going to stop. It’s the most frightened I’ve been, ever.”