Engineers began releasing water from the Addicks and Barker reservoirs on Monday to ease the strain on the 70-year-old dams, but the releases were not enough to relieve the pressure after one of the heaviest downpours in USA history, the Army Corps of Engineers said. Boats and kayaks are being used to reach people stranded on rooftops.
The hope was that a controlled release would prevent Addicks and Barker - which were built in 1945 and 1948 after previous catastrophic floods devastated downtown Houston - from spilling over and causing even more uncontrolled damage.
The Addicks and Barker reservoirs, built in the 1940s and created to withstand a "1,000-year flood", are both at record high levels following days of heavy rain.
President Donald Trump and his wife, Melania, were scheduled to visit Corpus Christi and Austin on Tuesday.
With more rain to come, the ongoing storm has already capped off a three-month period in which Houston has received almost a year's worth of rain, the National Weather Service says.
The 911 system in Houston has been at capacity throughout the night as rainfall has intensified from Tropical Storm Harvey.
The centre already held more than 9,000 people, nearly twice the number officials originally planned to house there, Turner said.
Trump will travel to Texas on Tuesday for briefings on the federal government's work to help the state recover from Harvey's devastation.
A Deal with The Devil? Hezbollah Now in Talks with ISIS
The province is southeast of Raqqa, where the U.S-backed Syrian opposition forces are battling ISIS militants. Hezbollah sources in Lebanon said the Islamic State had "succumbed under fire and asked for negotiations".
Calls for rescue have so overwhelmed emergency teams that they have had little time to search for bodies, and officials acknowledge that fatalities could soar once the floodwaters start to recede from one of America's most sprawling metropolitan centres.
Portions of Brazoria County, due south of Houston, had been under a mandatory evacuation notice since Sunday. In an update for our Newscast unit, Schneider adds, "The two reservoirs hold more than half a billion cubic meters of water combined".
Up to 3 inches could fall on eastern Harris, eastern Galveston and eastern Montgomery counties by Thursday morning, according to the National Weather Service.
The National Hurricane Center, though is still saying "relentless torrential rains" will continue over southeastern Texas and southwestern Louisiana.
The centre forecasts another 6 to 12 inches of rain across the upper Texas coast through to the weekend.
Local authorities of Houston and Rockport have reportedly confirmed the two deaths.
As of midday Monday, Harvey's center was "near or just off the Texas coast south of Matagorda" and moving at almost 5 miles per hour, the hurricane center said. "This may end up being one of the worst flood disasters in USA history".
Houston has been crippled by five consecutive days of rain from Hurricane Harvey, which has since been downgraded to a tropical storm after making landfall as a Category 4 hurricane late Friday.