"As a runway model, you have to keep your head up, you know," Welch, a former contestant on "The Bachelor" reality series, told KABC-TV. "So I didn't look down for a hole, particularly."
Then came the plunge. In the video, the crowd is heard howling with apparent shock. Welch, waist-deep in the hole, struggles to lift herself out, and is helped by "Heroes" actor Jimmy Jean-Louis, who modeled at the event. She regains her footing and exits stage left, raising her fist to seemingly signal that she's OK.
The video of the tumble, posted Thursday, had more than 1 million views on YouTube by Monday afternoon.
Welch, now an Internet celebrity, has a good sense of humor about it.
"It is just a really funny mishap. And I hope they're enjoying watching it just as much as I am," she said.