One of Houston's two major reservoirs overflowed Tuesday for the first time in its history, overburdened by torrential downpours from an "historic" storm.
The Addicks Reservoir crested above its 108-foot (32.9-meter) top, Jeff Linder, a meteorologist with the Harris County Flood Control District, said on Twitter.
The overflow happened one day after officials decided to allow emergency releases at the dam and the Barker Reservoir to thwart potential failures, staving off feared flooding in Houston's downtown area but jeopardizing thousands of nearby homes.
When officials decided to carry out the controlled releases, they said doing so would mitigate damage to surrounding neighborhoods.
"If we don't begin releasing now, the volume of uncontrolled water around the dams will be higher and have a greater impact on the surrounding communities," Galveston District commander Colonel Lars Zetterstrom said in a statement at the time.
Both levees are at record highs, and the Army Corps of Engineers is reportedly bracing for the Barker Reservoir to begin overflowing later Tuesday.
The dams are surrounded by residential areas in the western part of the U.S.'s fourth largest city.
Linder said officials were unable to measure water levels at the Barker Reservoir because the gauge flooded overnight.
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.
But the effects of widespread flooding prompted by nearly 50 inches (1.27 meters) of rainfall have overburdened search and rescue efforts.
At least six people have been reported dead due to the storm, which broke a state record for a tropical storm with 49.3 inches of rain it dumped in an area just southeast of Houston, according to the National Weather Service.
Responding to criticism of Houston Mayor Sylvester Turner's decision not to evacuate the city, Police Chief Art Acevedo told reporters this is an unprecedented catastrophic event.
"There is no hindsight for an event that's never occurred," he said.
United Nations Secretary-General Antonio Guterres is "following with great concern the flooding and extensive damage caused by Hurricane Harvey," his office said in a statement Tuesday emailed to Anadolu Agency.
Guterres is "saddened by the loss of life and extends his condolences to the government and people of the United States of America", the statement added
Shelters around Houston are filling up with more than 9,000 residents seeking refuge from the storm. Turner said the city is seeking additional space for "mega shelters" to house those in need.
President Donald Trump arrived in nearby Corpus Christi to tour affected areas.
As the storm heads east toward southwest Louisiana, New Orleans Mayor Mitch Landrieu said 13 of that city's 120 critical drainage pumps are not operational.
The system is critical for New Orleans, which sits below sea level near the Gulf of Mexico.
Landrieu and other officials warned residents that Harvey has the potential to create flash flooding.
