As relentless floodwaters continued to rise, thousands of Houston residents moved to higher floors and rooftops to avoid rapidly rising floodwaters. Emergency numbers – 911, 311, local police and Coast Guard – were overwhelmed with calls for help.

City officials confirmed in a news conference that emergency lines were at capacity.

So residents turned to social media.

“Help my sister and her 2 kids. They been waiting on coastguard for a whole day, NEED HELP,” one man tweeted Monday morning.

A woman pleaded: “We’re stranded and flooding in, please help us! There’s about 20 people, mainly kids!”

And an army of social media volunteers responded, urging residents to head for their rooms and wave sheets to help rescuers find them.

MORE: Plano granddaughter helps rescue her grandmother stuck in Houston

The Cajun Navy, a group of boat owners and operators made famous after Hurricane Katrina, took the lead, along with Texas search and rescue groups, in responding to social media pleas for help.

Using a walkie-talkie style app, dispatchers worked day and night to collect addresses and match them up with available volunteers in boats and high-water vehicles.

“Thirty people are on the roof,” a volunteer rescue organization blasted across the app Monday afternoon. “Their phones are dead. There are children. We’re hearing reports that several have already drowned.”

A website,, allowed volunteer rescuers to register and search for people near them in need.

Rescuers from as far away as Pensacola and Pennsylvania checked in with offers of help.

At 5 p.m. Monday, there were about 100 rescue requests on that site.

There have been eight confirmed deaths related to Hurricane Harvey and the flooding it brought to Houston. But the desperate pleas on social media suggested that number could be much higher.

Monday morning, a volunteer dispatcher kept a young woman on the phone while rescuers tried to find her house. The woman had experienced seizures and was confused; her medication was under water. She couldn’t find one of her children.

About 4:45 p.m. a desperate call went out for boats to respond to a nursing home.

The staccato drumbeat of requests was so rapid, it was difficult to distinguish individual requests.

4:56 p.m. “Can anyone hear me? We need help.”

4:57 p.m. “I have five different rescue requests. Are there any boats available?”

4:59 p.m. “Are there any boats available for a male and an infant, 1 week old?”

5 p.m. “Apartment complex with one adult and one child. They’ve been stranded for about 24 hours now and are taking on a lot of water.”

5 p.m. “I have two grandparents and two young children. They’re taking on water rapidly and need rescue as soon as possible.”

“We didn’t know how we were going to get out,” she said.

Unfortunately, the crisis seems long from over in Houston. Now a tropical storm, Harvey had moved back out to the Gulf of Mexico Monday evening and was gaining strength, spinning off heavier bands of rain across eastern Texas and southwestern Lousiana.