This map shows the cumulative calls for help compiled by the Harvey Relief and Harvey Rescue volunteer groups, which have gathered information from social media and through Google Forms. Many of these people have since been rescued.

“Someone send a boat our way 3 kids and 7 adults. one adult is a handicap mother that is diabetic who can’t walk in this water or get on a roof Please send someone!” Leticia Rodriguez, who lives in East Houston, posted on Facebook during threatening floodwaters.

Nowhere in the city did those cries for help on Twitter and Facebook seem more pronounced than its northeast corridor extending from Lake Houston and the San Jacinto River to nearly the city’s center.

Hurricane Harvey doused Houston with record-setting rainfall and flooding, bringing the nation shocking social media posts of people stranded and desperate for rescue.

BuzzFeed News spoke to nearly 30 people in those those three ZIP codes and two neighboring ZIP codes that saw a high volume of social media posts, offering a glimpse into how people used social media as they grappled with the devastation Harvey left behind.

BuzzFeed News crunched data compiled by a group of coders and organizers — some members of the #AltGov movement, one a Snopes employee, and some former government officials who worked on Katrina relief — known as @harveyrescue and Harvey Relief . They are compiling and mapping rescue requests from social media and entering them directly on a spreadsheet being circulated on social media. And while every post hasn’t been verified, and the list of posts isn’t definitive and is consistently evolving, it appears as though the highest concentration of distress calls came from three ZIP codes — 77044, 77049, 77078. The neighborhoods are largely black or Latino with relatively low incomes.

Many people reported that 911 calls were not going through to operators, and according to the Federal Communications Commission, 16 of the area’s 911 call centers were having problems dealing with the deluge of calls.

Houston officials pleaded with people to call 911 and hold the line if they needed rescue. But, unwilling to waste phone battery on call waiting, people or their friends and family members posted their location and details of their situation, replied to government accounts posting official information, and pleaded for help after waiting for hours with no food, no water, and without important medications. It seems most of the people have since been rescued.

“All the lines here were jammed,” East Houston resident Trina Moore said about 911. Her photo of her children on a kitchen counter with floodwater as high as the cabinets below them went viral. “It was just so many people needing help that you couldn’t get through. To me, it was easier to post on social media.”

The footage of people desperate for rescue evoked Hurricane Katrina in 2005. But unlike today, smartphones didn’t exist during Katrina. Twitter hadn’t been invented yet. And Facebook was still reserved for college students.

Some amateur rescue workers were monitoring the social posts. Jose Reyna, 33 — who has been responding to calls for help on social media since Sunday — told BuzzFeed News, “There’s just not enough boats to get to people.”

Reyna said he expects to see a jump in casualties, especially the elderly, sick, and people with disabilities.

“There was a cancer patient on support that lost power in the neighborhood, and I just couldn't get to him at that moment,” he said. Reyna has been going live on Facebook sharing where he is — and people commented and tagged others who need help.

The East Houston neighborhood — zip code 77078 — is 62.3% black and 32.6% is Hispanic or Latino of any race, according to Census data from 2015. More than 92% of the area’s population has not finished college and more than 60% of individuals makes less than $35,000 a year.

In the 77049 zip code, which includes parts of Channelview and sections of Sheldon, has a population of 31,111. Approximately 60% is Hispanic or Latino of any race and about 24% is black. The median individual income is about $26,500.

The 77044 area which includes Summerwood has a population of 37,753 with 45% being Hispanic or Latino of any race and 26% black. The median individual income is $38,225.

Rodriguez, 25, who ended up being rescued by a civilian — who told her he saw a screenshot of her Facebook post on Reddit — told BuzzFeed News she never saw authorities in her East Houston neighborhood.

“I don’t think they took us seriously,” Rodriguez said of officials.

Yolanda Jackson, 45, said she was waiting on the roof of her house with her husband and three children for almost 24 hours before she was rescued by a volunteer.

“We were out of food. Dehydrated. It was raining, and windy, and cold,” she told BuzzFeed News.

