Amid flooding, rainfall amounts varied widely with weekend storms

Some areas got ten inches, way too much for the pumps

Dave Cohen, WWL First News early edition
August 07, 2017 - 8:14 am

There are still loads of questions surrounding the rains that flooded several New Orleans neighborhoods on Saturday.

The New Orleans City Council is holding a hearing Tuesday to try and get some answers.

Many residents are asking why the water got so deep so fast.

WWL TV Meteorologist Dave Nussbaum says the biggest problem was that so much rain fell so quickly.

"It varied anywhere from six to eight inches, maybe a few spots as much ten inches," he explained.  "And that fell in a two to three hour time frame."

He says it was just too much for the flood control system and pumps to handle.

"When you have that much water; things get inundated, and they can't handle that much water."  

City officials said it was a very rare event.

"As much as 8 to 10 inches of rain fell in isolated areas of the city within three to four hours.  Many neighborhoods of the city saw rainfall amounts equaling a 1 percent chance of occurring in any year, a so-called 100-year event," according to a news release from the mayor's office.

The release says that the city’s drainage system can remove one inch of water from streets in its first hour of operation and a half-inch in subsequent hours. 

"The Sewerage & Water Board has reported that all 24 of its pumping stations were on and working throughout yesterday's event."

Mayor Mitch Landrieu's office stressed that it was just too much for the system to handle.

"There was widespread street flooding across the city, including in Gentilly, Lakeview, Mid City, Treme and the CBD."

Some have questioned if the new pumps at the outfall canals were operational.

The mayor's office says that was not a factor as the flood gates were open and it was not necessary to use the pumps.

"The permanent pump stations at the 17th Street Canal, London Avenue Canal and Orleans Avenue Canal were not operational as they are intended for use during a tropical storm surge event when the flood gates are closed.  They are not operational during heavy rains only."

Those pumps are only used if they flood gates are closed and the water can't flow out into the lake.

The isolated nature of the rain was notable too.  While some areas were inundated, the National Weather Service says others were not nearly as impacted.

New Orleans International airport only recorded half an inch of rain Saturday, Lakefront Airport got .49 inches and Slidell recorded 2.48 inches.  The New Orleans Downtown Heliport at the Superdome measured 5.49 inches.   

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