As more than 30 centimeters of rain deluged the nation's fourth-largest city, inundating homes, shutting down highways and leaving at least five people dead, Houston's mayor said there was no immediate solution.

Heavy flooding has become nearly an annual rite of passage in the practically sea-level city, where experts have long warned of the potential for catastrophe.

"I regret anyone whose home is flooded again," said Sylvester Turner, the city's mayor, on Monday. "There's nothing I can say that's going to ease your frustration. We certainly can't control the weather."

"A lot of rain coming in a very short period of time, there's nothing you can do," he added.

Flash flooding and more rain were expected later after some areas saw water levels approaching 50 cm. Scores of subdivisions were flooded, schools were closed, and there was no power to thousands of residents who were urged to shelter in place.

In addition to its location, Houston's "gumbo" soft soil, fast-growing population and building boom that has turned empty pastures into housing developments all over the city's suburbs and exurbs make it vulnerable to high waters, experts said.

Harris County, where Houston and many of its suburbs are located, has seen a 30 percent jump in population since 2000. Its surrounding counties have almost grown more than 10 percent since 2000, according to the Greater Houston Partnership, a business group.

'To die in a flood'

Some of the resulting developments include adequate greenspace for water runoff, but not all of them do, said Philip Bedient, an engineering professor at Rice University.

"Could we have engineered our way out of this?" Bedient said. "Only if we started talking about alterations 35 or 40 years ago."

Samuel Brody, director of the Environmental Planning & Sustainability Research Unit at Texas A&M University, last year called Houston "the No 1 city in America to be injured and die in a flood."

Rainstorms last year over Memorial Day weekend caused major flooding that required authorities to rescue 20 people, most of them drivers, from high water. Drivers abandoned 2,500 vehicles, and more than 1,000 homes were damaged in the rain.