HOUSTON—Across this city, residents came out to assess the damage Hurricane Harvey wrought on homes, churches and businesses and started the difficult task of clearing out furnishings, carpeting and keepsakes ruined by the record rainfall.

At the Norchester neighborhood in northwest Houston on Thursday, Beth Smith’s driveway was piled with ruined couches and end tables and carpeting soaked by the 4 feet of water that poured into her two-story home, the first time the 40-year-old house has flooded.

As she walked through the area where she has lived all her life, she pointed out homes where neighbors had been rescued. She wrinkled her nose at the musty, chemical smell that grew stronger near the standing water.

“You can smell oil, gasoline, anything you put in your garage,” she said.

A former consultant for a scrapbook company, the mother of two wiped away tears as she talked about returning home through knee-deep water to find most of their possessions waterlogged, including her daughters’ baby scrapbooks.

“I had to carry them out,” she said. “I was crying, taking them out.”

Hurricane Harvey is expected to be one of the costliest storms in U.S. history, affecting 100,000 homes and sending more than 30,000 people to emergency shelters around the state. At least 42 deaths have been attributed to the storm by local officials, a tally that is likely to climb.

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Harris County Flood Control District meteorologist Jeff Lindner tweeted that an estimated 70% of the 1,800-square-mile county, which includes Houston, was covered with 1½ feet of water.

But the storm’s wreckage on this sprawling city of 6.7 million was uneven. Businesses were open on one block but closed on the next; traffic signals worked at one intersection but not another. In the Coles Crossing subdivision along Cypress Creek in northwest Houston, some houses flooded with a foot or more of water while others were dry.

C.K. Fong, a 45-year-old software engineer, wore safety glasses while using bleach and a power washer to help his neighbor clean a flooded garage. Mr. Fong said he was feeling lucky that his own house didn’t flood, after watching from the window while water rose within a foot of his front door early Tuesday.

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“It was terrifying,” he said.

Next door, Csilla Fodor learned that her family would be kept out of her house for weeks, if not months, after water seeped into her 2,600 square foot home through weep holes in her walls.

“I don’t know what I’m hoping for at this point,” she said. “The good thing is we can at least rebuild. So many people are still underwater. I’m trying to hold on to that.”

At nearby Cypresswood Cleaners, the losses ranged from a wedding dress meant to be worn Saturday to the store’s computer system and the motor powering a $100,000 suit-cleaning machine. The bride was crestfallen when she showed up Wednesday in hopes of retrieving her dress, said owner Sam Dang.

“She cried but there’s nothing I can do,” he said.

Photos: Tropical Storm Harvey Causes Record Flooding in Texas The tropical storm dumped more than 50 inches of rain in parts of Texas in a new record for the contiguous U.S. Floodwaters from Tropical Storm Harvey surround homes and businesses in Port Arthur, Texas, on Thursday. Gerald Herbert/Associated Press 1 of 21 • • • • • 1 of 21 Show Caption Floodwaters from Tropical Storm Harvey surround homes and businesses in Port Arthur, Texas, on Thursday. Gerald Herbert/Associated Press

With the clothes floating in 4 feet of water, the tags came off items hanging from the bottom half of the mechanized racks, Mr. Dang said.

He said he purchased “a little, not enough” flood insurance after paying $20,000 in repairs after a 500-year flood in 2016. He said he can’t even estimate how much he will need to pay out of pocket to get his 2,750-foot store up and running, as there was twice as much water, and for a longer period, this time. The store employs 10 people and handles 800 garments a day, Mr. Dang said.

“We will try to rebuild,” he said. “This is how we make a living.”

Not far away at the sprawling campus of nondenominational church Bayou City Fellowship, crews of volunteers were buzzing about. Forty teams of 10 volunteers gathered supplies to help people needing assistance tearing up carpet, knocking out drywall and hauling out furniture and prized possessions.

None of the church buildings took in water, said Pastor Robbie Seay, but half the church parking lot was submerged, with a lone pickup truck sitting in water up to its wheel well.

It is eerie how some homes and neighborhoods in Houston flooded, while adjoining neighborhoods stayed dry, said Eric Moore, a church member. But he said it was wrong to say only some people were affected. With the widespread devastation and the city coming to a halt for a week, “everyone’s impacted,” he said.

Back in the Norchester neighborhood, Daniel Rawson was smarting at his bad bet. He closed on a two-story house in the tree-lined community on Aug. 15 and moved in last Thursday. The house had never flooded since its construction 40 years ago.

Mr. Rawson, 34 years old, said he and his wife and three young children didn’t even get to spend the night at the house before the flooding occurred. They deposited boxes and other goods and then sought permission to stay a few more nights in their former house across town.

On Thursday, he showed the debris marking the line where water filled the house, nearly 4 feet deep. The front yard was filled with cleaning supplies and plastic bins and the inside of the house had a dehumidifier and fans ordered by friends and family from Amazon on his behalf several days ago.

The contractors he had hired weeks ago to redo the kitchen were at work sorting through debris. Friends including Barry Mills nursed beers while they pulled up flooring.

“The generosity of people I haven’t met, and people I’m close to, is overwhelming,” he said. “Now it’s time to dry this place out and start over.”

Write to Valerie Bauerlein at valerie.bauerlein@wsj.com