Tropical Storm Harvey has continued to batter Texas, hurling record rainfall at the nation’s fourth-largest city, forcing thousands of people to flee their homes and testing flood control systems to their limits.
Parts of the Houston area saw more than 22in (55cm) of rain in a 24-hour period to Sunday evening; too much for the bayous to handle, too much for roads to remain passable and threatening to overwhelm emergency teams.
The army said late on Sunday that it planned to release water from two reservoirs south-west of the city in a bid to protect the city and surrounds. Water is to be released from the Addicks reservoir from 2am on Monday and from the Barker Reservoir about 24 hours later, the army engineer corps said.
The rising waters forced thousands of people to rooftops or higher ground as rescuers struggled to keep up with the constant calls for help. Helicopters landed near flooded freeways and high-water vehicles ploughed through water-logged intersections while some householders fled in kayaks or canoes or even swam to safety.
The Twitter account of the sheriff of Harris County, which includes most of Houston, was inundated with rescue requests and his team was unable to respond quickly to all of them. County officials said people should not call 911 if their lives were not threatened.
The White House said Donald Trump would visit Texas on Tuesday. By then, according to National Weather Service (NWS) statements, rainfall totals will be around 40in (101cm) or more on average in Houston, with some isolated spots hitting or exceeding 50in (127cm).
South-east Texas, including the Houston metropolitan area, was threatened by “significant to catastrophic flash flooding”, the NWS said, while neighbouring Louisiana also faced flash flooding as soils saturated.
It added: “Historic flooding is expected to continue in the Houston metropolitan area through the foreseeable future.”
Steve Bowen, chief meteorologist at reinsurance firm Aon Benfield, said: “What we’re seeing is the most devastating flood event in Houston’s recorded history. We’re seeing levels of rainfall that are unprecedented.”
More than 6.5m people live in the region, which is one of the country’s most flood-prone, with thousands of homes on floodplains and next to bayous and creeks. The city endured severe storms in 2015 and 2016 that caused loss of life and widespread damage. Early on Sunday, the NWS described events as “unprecedented and all impacts are unknown and beyond anything experienced”.
Texas governor Greg Abbott told a press conference 3,000 national guard and state guard troops had been activated, and 500 vehicles and 14 aircraft put into service. There were 250 highway closures around Texas, he said. Abbott also said he had not managed to speak to Houston mayor Sylvester Turner, despite calling him “several times”.
Houston’s office of emergency management said on Twitter that 911 received more than 56,000 calls from 10pm on Saturday to 1pm on Sunday, compared with 8,000 on an average day.
Two deaths have been confirmed but the toll was expected to rise as the storm triggered additional tidal surges and tornadoes, with parts of the region expected to see a year’s worth of rainfall in a week.
Harvey continued to send bands of rain to south-east Texas, long after it made landfall 200 miles away near Corpus Christi as a category four hurricane that first hammered coastal towns and the inland city of Victoria on Friday night. The evacuation of a city hospital was delayed by waist-high water but shelters were set up across Houston, including in a major convention centre.
The storm’s epic scale piled pressure on one of Houston’s most critical – and oldest – flood defence systems: US army reservoirs and dams 20 miles west of downtown.
Interstate highway 45 is submerged. Photograph: Richard Carson/Reuters
The Barker and Addicks reservoirs and dams were built in the 1940s and protect much of the city by controlling the amount of water that gushes into Buffalo Bayou, one of the rivers that winds towards the centre – languidly, in normal times. When water rises to extreme heights, constricting flow to the bayou to save central areas comes at the expense of places surrounding the dams. Water rushes west instead.
As Houston’s population has expanded, thousands of homes have been built near the reservoirs, which are under repair because the army engineer corps classified them as “extremely high risk” several years ago, though the federal agency has in the past denied they are under imminent danger of failing.
The release of water from the Barker and Addicks reservoirs would cause a rise of up to 6 inches (15 cm) per hour in the Buffalo Bayou – which runs through Houston – and would cause water levels to rise both upstream and downstream for a time. “This flood event will exceed the 2016 tax day flood elevations,” said Colonel Lars Zetterstrom at a press briefing. “Structures will be impacted upstream from both locations; the number of structures affected will depend on weather conditions.”
The corps said the flooding around the Barker reservoir might affect several thousand homes. It would take up to three months to empty the reservoirs, according to Zetterstrom.
Also on Sunday night, Fort Bend county, south-west of Houston, issued a voluntary emergency evacuation order on Sunday night for a neighborhood next to a reservoir that is set to see water released to protect much of central Houston. A statement said: “Imminent flooding is expected in the area. Residents are advised to make preparations now to remove all persons, pets, and livestock out of the flood-prone area.”
The storm also struck at the heart of the country’s oil and gas industry, forcing operators to close several refineries and evacuate and close offshore platforms. Gasoline futures rose 7%. Port Houston facilities would be closed on Monday.
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