Taming the water

A bout of devastating rain in the 1940s led to the floodcontrol system that protects South Florida’s people and property.

A September hurricane in 1947 brought 155 mph winds and 8 inches of rain. Another storm the next month deposited 11 more inches in the space of three hours.

Those storms, along with a tropical disturbance, dumped enough water to put 90 percent of southeast Florida under water. Some parts of Broward County were 8 feet under.

“It was a defining event for South Florida, and it led to the design what is now in place for flood protection,” MacVicar said.

South Florida’s floodcontrol system has some advantages when compared with Houston’s, Willoughby said.

The system’s network of man-made canals allow more water to be moved to the ocean and reservoirs than Houston’s system, which is more reliant on natural waterways, he said.

But no drainage system can conquer nature, said Lenny Vialpando, deputy director for Broward’s Environmental Protection & Growth Management Department and the county’s former flood plain manager.

About 40 percent of the county would be flooded in a 100-year storm event — about 15 inches of rain in a three-day period. A 500-year event — 20 inches of rain over a three-day period — would inundate 80 percent of the county.

The 50-plus inches brought by Harvey could swamp everything.

But predicting the flooding impact of a storm can’t be determined just by looking at rain totals, Vialpando said.

He said the amount of flooding would depend on many things: how saturated the ground was before the storm hit, how much canal water was released by water managers prior to the storm, where exactly the rain falls, does the deluge come during high tide?

The South Florida Water Management District has not done modeling on how 40 inches or more of rain would affect its system, said Randy Smith, an agency spokesman.

A storm like Harvey would be unprecedented, but emergency managers are now preparing for the possibility.

Emergency officials are now looking at the county’s flood plain to identify critical facilities — such as nursing homes and hospitals — that would need evacuation if record rains are being predicted, said Miguel Ascarrunz, emergency management director for Broward County. Keren Bolter, climate policy analyst for the South Florida Regional Planning Council.

Even storms that didn’t reach hurricane status have caused problems this year.

In June, heavy rain forced the closure of the Sawgrass Mills mall in Sunrise for three days. Earlier this month, several inches of rain that fell from remnants of Tropical Storm Emily overwhelmed Miami Beach’s drainage system, sending water spraying out of manholes and flowing through the streets.

Like Houston, South Florida hasn’t focused on the need to preserve open land to absorb rain, and as available land grows scarce, even golf courses are being converted into more homes, Bolter said.

“I am not against development, but at the same time, it’s not smart to build in these low-lying areas,” she said.

Researchers at State University Louisiana identified