For days, the rain came down in sheets, pounding Beijing and areas around it in what the government said was the heaviest deluge China’s capital had seen since record keeping began 140 years ago.

When the extreme downpour finally stopped on Tuesday, most of Beijing had been spared the worst — but partly because officials made sure the floodwaters went elsewhere.

Officials in Hebei Province, which borders Beijing, had opened flood gates and spillways in seven low-lying flood control zones to prevent rivers and reservoirs from overflowing in Beijing and the region’s other metropolis, Tianjin, state media said. The Communist Party leader of Hebei, Ni Yuefeng, said he ordered the “activation of flood storage and diversion areas in an orderly manner, so as to reduce the pressure on Beijing’s flood control and resolutely build a ‘moat’ for the capital.”

That move further inundated the adjacent city of Zhuozhou in Hebei, which had already been struggling to contain its own floods after a levee broke and a local river overflowed. Its streets and neighborhoods turned into a brown, muddy lake, with water up to 23 feet deep destroying homes and businesses.

Nearly a million people have been forced to evacuate in the province and in adjacent villages on the fringes of Beijing. In some areas, the flooding has disrupted power supplies as well as internet and mobile connections. Residents have posted online pleas for help finding hundreds of missing people.

China is not the only country that sometimes opens spillways to divert floodwaters from big cities to areas with fewer residents — an emergency, last-resort measure aimed at reducing destruction and loss of life. The Morganza Floodway in central Louisiana, last opened in 2011, has 125 huge gates that can open to drain floodwaters coming down the Mississippi River away from New Orleans and into the sparsely populated, swampy Atchafalaya Basin.

But in China, the crisis in Zhuozhou has set off widespread anger, in part because help was initially slow to arrive in some areas, leaving many stranded. Survivors have also complained that they were not given ample warning about the discharge of floodwaters, and questioned if they would be compensated for their losses.

In particular, people have denounced what they perceive as a Hebei leadership that has been more interested in appeasing national leaders in Beijing than in safeguarding millions of Chinese citizens. Mr. Ni’s “moat” comment, seemingly insensitive to the losses endured by his residents, became a hashtag that quickly amassed more than 60 million views before censors began suppressing the online discussion.

“To protect Beijing, no one cares if we in Hebei are being flooded,” a resident of a village on Zhuozhou’s outskirts complained on Friday morning, speaking on condition of anonymity for fear of reprisal for criticizing the government.

Another Zhuozhou resident stood at the edge of a field next to his partly submerged village on the city’s outskirts on Friday, waiting for lingering, thigh-deep water to subside. He said that he had put his belongings on chairs and put the chairs up on beds before fleeing his house as the waters rose. But water flowed at least six feet deep through his home, ruining his possessions and destroying his nearby pile of construction materials.

“No one ever informed us of the flood discharge or told us to prepare to evacuate — if we had known this information, we would not have left so many things behind,” said the villager, who gave his family name, Yu. “Everything is soaked in water. I can barely calculate my loss.”

Crumpled chunks of steel siding, a white dressing table and a steeply leaning wood shed were strewn across the field near Mr. Yu, showing the force with which floodwaters had surged through the area.

The driver of a large yellow front loader used its bucket to carry a gray-haired woman in a wheelchair out of a deeply flooded street, then carried cases of drinking water in to residents still there. A gray minivan towing two red inflatable motorboats waited nearby to enter the neighborhood.

The government and party have set aside at least $20 million for flood prevention, relief and reconstruction efforts in Beijing and Hebei; another $63 million was allocated on Friday to Beijing, Tianjin and Hebei for the restoration of dams, reservoirs and other water facilities. Zhuozhou’s government issued a national appeal on Thursday for donations of money and relief supplies.

The official China Daily newspaper published a commentary that called for residents who suffered losses because of the flood diversion to be compensated, as required by Chinese law at least for those living in designated flood diversion areas. It said the authorities should be better prepared for future disasters, describing the recent deluge as a “wakeup call.”

“Ensuring the safety of people in flood diversion areas, ensuring adequate compensation, and assisting in the swift reconstruction of their homes and livelihoods are essential aspects of disaster management,” the newspaper said.

But the flooding extended beyond designated diversion areas, which could complicate compensation. And many living in Zhuozhou are migrants from other provinces who lack legal residency in Hebei.

“Do you think we migrants are eligible to receive compensation?” said another resident, who makes a living by gathering discarded trash in Beijing and selling it to recyclers in Hebei. “It’s impossible.”

The flooding wreaked havoc elsewhere in Zhuozhou: a book publisher lost more than $3.5 million worth of books in a single hour; some animal shelters were inundated.

Two Chinese partner groups of Humane Society International, the Capital Animal Welfare Association in Beijing and Dalian Vshine, estimated that floodwaters carried away 400 dogs and 300 cats from shelters, although some were later found clinging to rooftops and treetops downstream.

Much of the water flowing through Zhuozhou did not come from Beijing. State media said that downpours in the mountains of Hebei had caused Hebei’s Juma River to flood in Zhuozhou. A levee on the nearby Baigou River, into which the Juma River flows, gave way near Zhuozhou, forcing the evacuation of four villages.

But state media also reported that during a severe flood in Beijing and Hebei in 2012, which killed 145 people and left 26 people missing, the water barely reached the doorsteps of Zhuozhou residents.

During previous inundations of southwestern Beijing, the water had somewhere else to go: a vast expanse of fairly low-lying land in the Xiong’an area of Hebei along the Beijing border. But in the past decade, China’s top leader, Xi Jinping, has ordered extensive construction in Xiong’an, to develop the area into an alternate capital.

Many municipal government agencies and state-owned enterprises have been required to move to the “Xiong’an New Area,” to relieve crowding in downtown Beijing.

China has also built one of the world’s largest international airports in southernmost Beijing next to the Hebei border, with five runways instead of the usual two or three. After commercial jetliners ended up sitting wheels-deep in water there on Monday, closing the airport, top officials ordered action.

“Ensure the absolute safety of key defense targets such as Xiong’an New Area and Beijing Daxing Airport,” Li Guoying, China’s minister of water resources, ordered on Tuesday.

China has for several years been dealing with extreme weather emergencies across the country. The world’s heaviest single hour of rain ever recorded in a major city occurred two years ago in the central city of Zhengzhou, flooding a subway train and road underpasses. This week’s downpour along the Beijing-Hebei provincial border, with almost 30 inches of rain falling in northwestern Beijing, came soon after the most severe heat wave in Beijing since modern temperature readings began in 1961.