BROWNSVILLE, Texas (CNN) -- A downgraded Hurricane Dolly caused damage as it made landfall in Texas on Wednesday afternoon and brought the possibility of flooding over the next two days.
Dolly made landfall on South Padre Island, Texas, about 2 p.m. ET, tearing roofs off homes, flooding streets and sending residents scrambling for safety from wind gusts reaching 120 mph.
At least one person was injured as sustained winds up to 100 mph downed power lines and tore observation decks off homes and condos, CNN affiliate KPRC reported.
A 17-year-old fell from a seventh-story balcony, sustaining head injuries, a broken leg and a broken hip. He is alert and receiving treatment on the island while authorities wait for the first opportunity to get him to the mainland, KPRC reported.
Later in the day, sustained winds decreased to 85 miles an hour, prompting authorities to downgrade the hurricane to a Category 1.
"When we heard the first bang, I thought it was one of the air conditioners flying," said Jacqueline Bell, who lives on South Padre Island. "Then we went outside, and we saw the debris, and we saw the neighbors leaving."
A hurricane warning remained in effect for the coast of Texas from Brownsville to just south of Baffin Bay and for the northeastern coast of Mexico from Rio San Fernando north to the U.S. border.
But warnings in other areas had been lifted or, as in Corpus Christi, Texas, downgraded to a tropical storm warning.
CNN meteorologist Chad Myers said persistent rainfall could cause flooding upstream in the Rio Grande as long as the storm stalled over the mountains of Mexico.
Meyers said it could take two days for the rainwater to flow upstream and challenge the natural levees, which were holding for now.
"The levees are holding up just fine," said Johnny Cavazos, emergency coordinator for Cameron County, The Associated Press reported. "There is no indication right now that they are going to crest."
Even before Dolly made landfall, driving rain and wind gusts from its outer rings flooded streets and threatened to pour into homes while wind gusts shattered windows on the island popular with tourists.
The 2,400 residents began bracing for the storm Tuesday night, when strong winds forced the closure of South Padre Island's causeway to the mainland. Officials said the causeway is closed any time winds reach 39 mph.
Some chose to remain on the island and wait out the storm.
Steven Murphy took shelter with his girlfriend in his 65-foot double-decker fishing boat, Murphy's Law, and hoped for the best.
Murphy, who owns a charter fishing company with his brother on the island, lived through a more powerful hurricane, where he saw boats bigger than his tossed onto land.
"I had nightmares about that last night," he said from his boat Wednesday.
He said the wind outside sounded like a tornado and added that he'd seen several items blow past the windows of his vessel.
"It's starting to tear it up real good," Murphy said.
On the mainland, people in the path of the storm stacked sandbags around their homes, nailed plywood over windows and prepared generators to keep power going in the event of a blackout.
Maribel Vallejo of Brownsville waited in line for two hours Tuesday for bags of sand.
"It's something we have to do to avoid any flooding going into our homes," she said.
Some people unknowingly traveled into the danger zone.
Pedro Martinez Sanchez was stuck in Brownsville, Texas, on Wednesday after he and his wife drove 12 hours from Veracruz, Mexico, to do some shopping.
He said he had no idea that the hurricane was coming when he scheduled the trip. He had planned to leave Wednesday but now would be stuck in a motel until the danger had passed.
Brownsville Mayor Pat Ahumada said that the storm downed trees and dumped 6 to 8 inches of rain but that emergency workers were ready to respond once the wind and rain died down.
Ahumada said reports that the city's levees are in danger of breaching were exaggerated.
He said it would take 20 inches of rain to top nearly all of the city's levees, which had been reinforced to federal standards or above.
"People think we're facing a Katrina," he said. "That's not the case."
More than 13,000 customers were without power in Cameron County, where Brownsville is, utility company AEP Texas told The Associated Press.
Dolly's arrival also had the military scrambling. The Navy moved 89 aircraft from its Corpus Christi post to other locations in Texas and New Mexico.
Texas Gov. Rick Perry issued a disaster declaration for 14 counties before Dolly arrived. The declaration "allows the state to initiate necessary preparedness efforts," according to a statement from Perry's office.
More than two dozen state agencies and organizations, including the Red Cross, are on standby to help with evacuations and other needs.
The National Guard has set up staging areas in Houston, Austin and San Antonio, officials said. As many as 1,200 National Guardsmen have been called to help, and 700 are deployed to targeted areas.
An incident management team has been pre-positioned in South Texas, including six UH-60 helicopters, to provide support to first responders.
"We have been preparing for this kind of event for well over a year," said Col. William D. Meehan, a spokesman for Texas Military Forces.
Some people appeared to try to take advantage of what they believed would be the distraction of law enforcement.
"Often times during these type of tragic circumstances, criminal organizations try to exploit what they believe to be is a weakened position of law enforcement," Jayson Ahern, deputy commissioner with U.S. Customs and Border Protection, said Wednesday.
Ahern said authorities stopped three groups suspected of engaging in illegal smuggling into the United States from Mexico as the hurricane approached.
One group was trying to smuggle an estimated 5,000 to 8,000 pounds of marijuana on a truck that was stopped on U.S. 77 south of Kingsville, Texas, officials said.
The other two groups were believed to be trying to smuggle in illegal immigrants, Ahern said.
