Harvey: Thousands await rescue as estimated 30,000 to 40,000 homes destroyed in Houston area The storm made its third landfall Wednesday morning, west of Cameron, Louisiana.

 -- Thousands of people likely remain stranded, and an estimated 30,000 to 40,000 homes have been destroyed in the Houston area as Hurricane Harvey, now a tropical depression, continues to batter the Gulf Coast with torrential rains, flooding and strong winds, Harris County Judge Ed Emmett said.

Harvey made its third landfall, just west of Cameron, Louisiana, Wednesday at 4 a.m. CDT, with maximum sustained winds of 35 mph, according to the National Weather Service. As of 11 p.m. EDT, the slow-moving storm had picked up some speed, moving northeast at 9 mph, with its center was about 30 miles northeast of Alexandria, Louisiana.

The storm was starting to fall apart overnight, with rain scattered in nature and falling over Mississippi and Arkansas. Residents in western Tennessee, around Memphis, should expect heavy rains on Thursday morning and possible flash flooding as up to 8 inches of rain are possible locally.

Before that, it battered the Beaumont-Port Arthur area in southeastern Texas, dumping more than 2 feet of rain in some parts. By Wednesday evening, the storm had weakened from a tropical storm to a tropical depression.

"We have people who are on the second floor of their homes. They're riding it out, and they're waiting for the waters to go down," Emmett, who is also the director of Texas' Harris County Office of Homeland Security and Emergency Management, said in an interview Wednesday with ABC News Chief Anchor George Stephanopoulos on "Good Morning America."

"We've got probably [30,000] to 40,000 homes that have been destroyed," Emmett added.

Power outages in the Houston area are down to 75,000, but 32,000 of those outages are inaccessible to crews, officials said Wednesday.

The brunt of the storm's impact has begun to shift to western and northern Louisiana. Now, for Harris County, "the biggest challenge is going to get people back in their homes," Emmett said. "We've got to get those people back into their normal lives as soon as possible."

The Houston Airport System announced that it has lifted restrictions on commercial operations. On Saturday, Southwest Airlines will ramp up the number of flights, according to the airport system.

A curfew from midnight to 5 a.m. will take effect in Houston for the second night in a row, Mayor Sylvester Turner said in a press conference. No arrests were made during Tuesday night's curfew, a spokesperson for the Houston Police Department said at the press conference.

The Houston Fire Department has received about 15,000 calls for assistance, a spokesperson said Wednesday evening. The fire department will begin recovery operations in certain areas and conduct door-to-door checks of accessible homes that got more than 3 feet of water, the spokesperson said.

Houston Police Chief Art Acevedo said 911 calls for water rescues were down to about 40 an hour as of this morning. Still, the Coast Guard is taking more than 1,000 calls per hour from people needing rescue.

The Navy is sending two ships -- the USS Kearsarge and the USS Oak Hill -- to the Gulf of Mexico to held with storm relief efforts, it announced Wednesday.

Vice President Mike Pence said on Wednesday that he will travel to Texas Thursday. "@POTUS asked me to travel to Texas tomorrow with his message: 'We will be with you every single day to restore, recover, and rebuild,'" the vice president tweeted.

Harris County Flood Control District meteorologist Jeff Lidner told reporters this morning that the lowest homes near the Addicks and Barker reservoirs have 3 to 6 feet of water.

Harvey, which first came ashore last Friday in Texas as a category 4 hurricane, dumped more than 51 inches of rain on some parts of the state, according to preliminary reports from the National Weather Service. The storm led to at least 31 deaths over the past five days, according to The Associated Press. Harris County officials, where Houston is located, confirmed six new deaths late Wednesday.

Texas Gov. Greg Abbott -- who spoke by phone Wednesday with the president while the commander in chief was on board Air Force One, returning from Missouri -- said most of the deaths were due to people driving vehicles into high water.

An undetermined number of people are missing. The Coast Guard is leading a search for two volunteer rescuers missing after their boat crashed and capsized on Cypress Creek near the North Freeway early Wednesday. Authorities found a third rescuer clinging to a tree, according to the Harris County Sheriff's Office.

The Harris County Sheriff's Office urged people awaiting rescue to "hang a towel or sheet prominently" for rescuers to see because addresses are difficult to spot.

Harvey is expected to weaken and continue moving to the north and east across the Lower Mississippi Valley and Tennessee Valley through Thursday. But the National Weather Service said Harvey still has the potential to cause "life-threatening flooding."

"Catastrophic and life-threatening flooding continues in southeastern Texas and portions of southwestern Louisiana," the service said in an advisory this morning. "Excessive runoff from heavy rainfall will cause flooding of small creeks and streams, urban areas, highways, streets and underpasses, as well as other drainage areas and low-lying spots."

The situation became serious in eastern Texas Wednesday. The National Weather Service issued a flash-flood warning for parts of southeastern Texas, including the cities of Beaumont and Port Arthur, which received more than 26 inches of rain in some areas on Tuesday alone.

Port Arthur Mayor Derrick Freeman urged residents to get to higher ground in a Facebook post early Wednesday.

"Our whole city is underwater right now but we are coming!" Freeman wrote in one post. "Please get to higher ground if you can, but please try stay out of attics."

The largest oil refinery in the United States is shutting down because of the devastating floods. Its owner, Motiva Enterprises, announced in a statement early Wednesday that it began a "controlled shutdown of the Port Arthur refinery in response to increasing local flood conditions."

The refinery won't reopen until floodwaters recede, the company said.

Officials were forced to evacuate the shelter at the Bob Bower Civic Center in Port Arthur this morning after it began to fill with water. One witness, who was forced to relocate, said some areas of the center had almost 4 feet of water inside.

Displaced residents were taken to a secondary evacuation site at the Carl Parker Center, according to ABC Texas affiliate KBMT-TV.

The disastrous rainfall Wednesday led the National Weather Service to further extend a flash-flood emergency for the cities of Beaumont and Port Arthur until 4:30 p.m. CT in anticipation of additional rain that morning.

The worst is not over for Texas, Abbott warned Wednesday. He said 24,000 National Guard troops, including all of Texas' force, have been deployed in the state and will be crucial in the weeks and months to come to help restore order.

The National Guard has made 8,500 rescues, evacuated 26,000 people and done 1,400 shelter-in-place welfare checks in Texas so far. Meanwhile, there are 32,000 people in shelters throughout the state, Abbott said.

Five days after Harvey first made landfall, FEMA said it's still in "life-saving, life-sustaining" mode, with recovering survivors being the top priority. FEMA Administrator Brock Long said at a news conference Wednesday that there are more than 12,000 emergency staffers on the ground in Texas and Louisiana, spread across 50 counties. The agency is operating more than 230 shelters in Texas, housing more than 30,000 people.

The George R. Brown Convention Center in Houston is no longer accepting evacuees, Turner said. About 8,000 people are currently at the convention center, down from 10,000 people on Tuesday night. The city had opened up the Toyota Center as an additional shelter to ease the overcrowding at the convention center.

Long said the FEMA travel trailers used after Hurricane Katrina are a "last resort" and the agency will first try to move displaced residents into local hotels before helping them clear out their inundated houses so they can return to them. FEMA has already placed more than 1,800 flood survivors in hotels, he said.

The Air Force said it was providing aircraft assistance in response to Harvey, including two HC-130J Combat King IIs, three HH-60G Pave Hawks, air crews and other support personnel to College Station, Texas. Two C-17 Globemaster IIIs are carrying more than 30 tons of relief supplies to Louisiana's Alexandria International Airport.

Help is also coming from overseas. Gov. Abbott said on Wednesday that Texas is accepting resources from Mexico, including boats, food and other supplies. And Israel's embassy in Washington tweeted, "A team from the Israeli Rescue Coalition will arrive in #Houston on Thursday to help victims of #HurricaneHarvey."

ABC News' Max Golembo, Serena Marshall, Whitney Lloyd, Luis Martinez and Zunaira Zaki contributed to this report.

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