Officials with the county said they had contingency plans in place for such an emergency.
"We did see a huge increase in call volume during that time span," 911 coordinator Kathi Yost said.
Yost said the 911 system never went down even though their main call center was without power.
"We never lost communication with our first responders. We never lost communication with the citizens," she said.
During Tropical Storm Allison, Yost said a similar emergency happened and, though they maintained communication with the public, they lost the ability to speak to first responders.
After the power outage last week, 911 calls immediately transferred to the Greater Harris County 911 call center. Personnel eventually transferred there as well, Yost said.
However, many people reported frustrations and delays. Officials said to stay on the line, but frustrated callers hung up.
"It's like they just said forget about [them]," Jason Orphey said.
Orphey lives in Kashmere Gardens in northeast Houston, which was badly flooded. He was able to drive his truck out, but his neighbor called 911 trying to get a 94-year-old woman to safety.
They never made it through to an operator. Volunteers eventually got her out, neighbors said.
Orphey said his neighborhood is full of similar stories.
"The neighbor directly across the street from me had the same situation. I couldn't even reach her from where I was. I can't walk through five feet of water and pick up a woman who can't walk," he said.
Now that the rescuing is over for the most part, people in northeast Houston still fear being forgotten during recovery efforts.
Many voiced frustrations with FEMA and criticized city leaders for sending resources like trash collecting trucks to more affluent areas like Kingwood.
"I don't have housing. I'm still sleeping in my truck," Orphey said. "You were able to save the majority of us from flooding, from drowning but where's the help now?"
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